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Luigi ROVATI

Professore Ordinario presso: Dipartimento di Ingegneria "Enzo Ferrari"


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Pubblicazioni

- DEVICE CONNECTABLE TO A MACHINE FOR EXTRACORPOREAL TREATMENT OF THE BLOOD OF A PATIENT [Brevetto]
Carletti, Umberto; Cattini, Stefano; Lodi, Lorenzo; Lugli, Lorenzo; MAZZA CARLO, Martino; Meglioli, Davide; Rovati, Luigi
abstract

A device connected to a machine (29) for extracorporeal treatment of blood of a patient comprises a sensor element (17) positionable on the patient's body for detecting the electrical potential (VI) of the blood in the patient's body and varying means (18) for modifying the electrical potential of blood treated by said machine (29), the varying means (18) being so programmed as to make the difference between the electrical potential (V2) of the blood exiting said machine (29) and the electrical potential (VI) measured by the sensor element (!7) lower than present value.


- dispositivo collegabile ad una macchina per il trattamento extracorporeo del sangue di un paziente [Brevetto]
Carletti, Umberto; Cattini, Stefano; Lodi, Lorenzo; Lugli, Lorenzo; MAZZA CARLO, Martino; Meglioli, Davide; Rovati, Luigi
abstract

L’invenzione concerne un apparato per trattare il sangue20 di un paziente al di fuori del corpo umano,particolarmente un apparato per la circolazioneextracorporea, ossia un apparato che consente ditrattare il sangue di un paziente al di fuori del corpodel paziente stesso esercitando temporaneamente la25 funzione di propulsione circolatoria normalmenteesercitata dal cuore e la funzione di ossigenazionenormalmente esercitata dai polmoni.


- INTERFEROMETRICAL, OPTICAL RETROREFLECTION WITH LOW COHERENCE SOURCE [Brevetto]
Rovati, Luigi
abstract

Carrying out measurements of distances and thicknesses also in the presence of optical/electronic disturbances and noises and in industrial environments by means of interferometric optical retroreflection using incoherent light with superluminescent diodes.


- Method and Apparatus for Non-invasive Measurements of Blood-glucose Levels in Humans [Brevetto]
R. R., Ansari; Rovati, Luigi
abstract

An apparatus (10) for determining a diagnostic glucose level in a human subject includes a light source (30) that produces collimated light at a selected wavelength. The collimated light is arranged such that it passes through a portion of an eye (12) of the subject and reflects off an eye lens (16) at a selected angle (.theta..sub.B) as reflected light. A polarization analyzer (70) measures a polarization of the reflected light that exits the eye (12). A path length processor (68) determines an optical path length (L.sub..lambda.) of the reflected light within an aqueous humor (22) of the eye (12). A glucose level processor (90) computes a glucose concentration based on the measured polarization and the determined optical path length (L.sub..lambda.).


- METHOD AND DEVICE FOR MEASURING THE LEVEL OF SECONDARY RADIATION PRODUCED BY PRIMARY RADIATION INCIDENT ON A ZONE OF AN OBJECT [Brevetto]
Ricka, Jaroslav; Frankhauser Franz, Jun; Duerr, Ulrich; Rovati, Luigi
abstract

n order to measure the level of secondary radiation (4, 25) produced by primary radiation focussed on a zone (5) within an object (3), the invention calls for the primary and secondary radiation coming from or going to the zone (5) to be directed, in a common beam (17, 25), towards the same optical element (21) which focusses the primary radiation and collimates the secondary radiation into an optical fibre (30) leading to a measuring unit (29). In this beam, the primary and secondary radiation (i.e. the radiation transmitted into and retransmitted by the zone (5)) are conveyed parallel and cylindrically coaxial, but spatially separated from each other. Scattering and luminescence of light which can come only from the zone (5) within the object can be measured or otherwise determined. In addition, a relatively high light intensity can be produced at certain points within the object (3) being examined, the light intensity rapidly decreasing outside the object so that there is no danger of damage to the surrounding areas or the walls of the object (3). It is also possible to determine scatter and luminescence in the interior (1) of an object (3) which is only accessible to rays via an aperture (32), the position of the scatter and luminescence zone (5) being definable to such a degree of certainty that it can be kept away from radiation-sensitive zones.


- METHOD AND INSTRUMENT FOR THE NON-INVASIVE MEASUREMENT OF THE OXYGENATION/SATURATION OF BIOLOGICAL TISSUE [Brevetto]
A., Bandera; M., Donini; Rovati, Luigi
abstract

An instrument for the measurement of the oxygenation/saturation of biological tissue comprising at least one optical source generating continuous intensity luminous radiation, an optical probe to convey the radiations onto a part of the tissue and to collect the radiations in exit from the tissue at a set distance, a receiver unit and an electronic control unit. The instrument is adapted to interface to a personal computer in order to obtain indicative absolute levels of the oxygenation of the tissue based on the collected signals. The optical source is made up of at least three independent optical modules for the emission of the same number of different luminous radiations with wavelengths belonging to the near infrared spectrum, with at least one of said wavelengths in correspondence to a water absorption peak.


- METHOD FOR MEASURING A FLUID VELOCITY AND RELATED APPARATUS [Brevetto]
Norgia, Michele; Porro, Giampiero; Pozzi, Roberto; Rovati, Luigi; Torinesi, Alessandro
abstract

A method for measuring the mean velocity (VH) of an extracorporeal blood fluid or infusion fluid, by means of retroinjection interferometry, comprises the step of emitting a first laser light beam (41), from the laser cavity (40) of a semiconductor laser source (60), reflection of a second laser beam (45) by the fluid (50) and consequent generation of interference with the first laser beam (41) inside the laser cavity (40), detection of the interference signal by a monitoring photodiode (46), and processing, by means of an electronic processing and control circuit (100), of the interference signal detected. The invention also comprises an apparatus (62) for implementing the method described and an extracorporeal circuit (58) comprising said apparatus. The invention also comprises a method for replacing a laser source in said apparatus.


- Metodo di misurazione della velocita' di un fluido e relativa apparecchiatura. [Brevetto]
M., Norgia; G., Porro; R., Pozzi; Rovati, Luigi; A., Torinesi
abstract

The present invention relates to a method for measuring the velocity of fluids, in particular infusion fluids, used generally in the sanitary field, or blood flowing in extracorporeal circuits, and the description which follows is provided with reference to this area of application solely in order to simplify illustration thereof. The invention also relates to the apparatus for implementing this method. Measuring the velocity of the fluid is useful for obtaining other important measurements such as the flowrate within a pipe.


- metodo e strumento per la misura non invasiva dell'ossigenazione⁄saturazione di un tessuto biologico [Brevetto]
A., Bandera; M., Donini; Rovati, Luigi
abstract

metodo e strumento per la misura non invasiva dell'ossigenazione⁄saturazione di un tessuto biologico


- Monitoring of retinal temperature during laser therapy [Brevetto]
Rovati, Luigi; G., Staurenghi
abstract

In a laser eye treatment apparatus, a probe light source generates a secondary emitted light emanating from a treatment area of retinal tissue that is irradiated by a treatment light source. An optical detector detects the secondary emitted light. A processor statistically analyzes the secondary emitted light to determine a temperature of the treatment area of retinal tissue.


- poligono di tiro [Brevetto]
Pancaldi, Fabrizio; Rovati, Luigi
abstract

L’invenzione descrive un poligono di tiro comprendenteuno schermo (5), su cui vengono proiettate immagini dibersagli (9) e su cui tiratori sparano con armi diqualsiasi natura, mezzi emettitori (17) di fasci diradiazioni diretti verso lo schermo (5).Un’unità di controllo (30) si occupa di rilevare un tiroe di calcolare se è stato realizzato un centro. [FIG. 1]


- Procedimento per effettuare misure di distanze e di spessori mediante retroriflessione ottica e relativa apparecchiatura [Brevetto]
Rovati, Luigi
abstract

Procedimento per effettuare misure di distanze e di spessori mediante retroriflessione ottica e relativa apparecchiatura


- sistema di antifurto per biciclette e oggetti in genere [Brevetto]
Aliscioni, Marco; Artioli, Alberto; DELLA CASA, Emiliano; Rovati, Luigi; Tesauri, Lorenzo
abstract

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2020 - Characterization of a premixed flat combustor through plasma current measurements [Relazione in Atti di Convegno]
Pintori, Luca; Verzellesi, Giovanni; Rovati, Luigi
abstract

Chemical reactions inside hydrocarbon flame can generate charged species that can be collected by a polarized electrode placed near the flame front. Such current can give valuable information about the combustion status. In this paper, methane combustion was investigated analyzing the current-voltage characteristic curves at different thermal loads and gas mixture fractions. The considered experimental setup consists of a flat burner at the atmospheric pressure where certain premixed fractions of air and fuel were fed to. A preliminary simple model was introduced to describe the characteristic system response and the relation between fitting parameters and different combustion regimes has been discussed.


2020 - Comparison of the VLP-16 LiDAR system with an absolute interferometer [Relazione in Atti di Convegno]
Cattini, S.; Rovati, L.; Di Cecilia, L.; Ferrari, L.
abstract

Many new technologies for ADAS are emerging in recent years. In this scenario, LiDARs are becoming one of the pillars for environmental sensing needed in ADAS.Driven by the automotive industry, nowadays many new manufacturers are continuously putting new LiDAR systems on the market, thus increasing LiDARs availability and concomitantly reducing prices. As a result, LiDARs are today finding many new applications in fields such as agriculture and industrial automation.In this paper, we describe and discuss a measurement procedure for the analysis of the performances of LiDARs and, we report the results obtained from the characterization of one the most widespread LiDAR systems -namely VLP 16 by Velodyne. In particular, we compare the estimates provided by the LiDAR with the estimates provided by an absolute interferometer. To the best of our knowledge, these are the first published data obtained comparing a LiDAR and an absolute interferometer.The proposed tests investigated both warm-up and stability and, errors in the measured coordinates.The obtained results indicate a warm-up times of about 42 min and errors of few millimeters over a measuring interval of about (2, 21) m.


2020 - Design and performance of a hyperspectral imaging system: Preliminary in vivo spectral reflectance measurements of the human iris [Articolo su rivista]
Di Cecilia, L.; Rovati, L.
abstract

In this paper, we present a novel hyperspectral system designed for imaging the human iris in vivo. The instrument is based on a tunable light source (from 480 nm to 900 nm) and a monochrome camera. The system can acquire hyperspectral cubes in 4 s, with spatial and spectral resolutions of 11 μm and 20 nm, respectively. The optical characterization of the new instrument is described, and we demonstrate its safety with respect to ANSI standards. Preliminary in vivo measurements in human volunteers are also presented.


2020 - Optical characterization of the beams generated by 3D-LiDARs: proposed procedure and preliminary results on MRS1000 [Articolo su rivista]
Cattini, Stefano; Di Cecilia, Luca; Ferrari, Luca; Rovati, Luigi
abstract


2020 - Performances and robustness of a fluorescent sensor for nearly-neutral pH measurements in healthcare [Articolo su rivista]
Cattini, Stefano; Truzzi, Stefano; Accorsi, Luca; Rovati, Luigi
abstract


2019 - Guest editorial guided lightwaves for sensors and measurement systems: Advanced techniques and applications [Recensione in Rivista]
Xiao, G. G.; Guo, T.; Rovati, L.; He, Z.
abstract


2019 - On the feasibility of Absolute Distance Measurement by using Optical-Feedback into a Superluminescent Diode Cavity [Articolo su rivista]
Rovati, Luigi; Di Cecilia, Luca; Cattini, Stefano
abstract

The development of accurate absolute distance interferometers is a long-term research goal. The key impact of this paper is the demonstration of an absolute distance interferometer based on the optical-feedback into a superluminescent diode cavity. Thanks to the optical-feedback, we obtained huge interference fringes even with diffusive targets and without using high-sensitivity and low-noise detectors, but directly exploiting the monitor photodiode enclosed in the same package of the optical source. The low coherence of the optical source makes the system robust to any stray-light along the optical path and thus suitable to work in biological media and dusty industrial environments. The proposed signal processing exploits a zero-crossing approach to determine the absolute target position. Preliminary results show a 95% expanded uncertainty to measuring interval ratio of about 60 ppm over a measuring interval of 50 mm.


2019 - Optical feedback into a superluminescent diode cavity for absolute distance measurements [Relazione in Atti di Convegno]
Rovati, L.; Cecilia, L. D.; Cattini, S.
abstract

The development of accurate absolute distance interferometers is a long-term research goal. The key impact of this paper is the development of an absolute distance interferometer based on the optical feedback into a superluminescent diode cavity. The proposed approach employs a two arms interferometer feeds by a superluminescent diode. Thanks to the optical feedback, we obtained huge interference fringes even with diffusive targets. The proposed signal processing exploits a zero-crossing approach to determine the absolute target position. Preliminary results show a ratio between measurement uncertainty and range of about 50 ppm.


2019 - Performance analysis of a hyperspectral system for human iris imaging [Relazione in Atti di Convegno]
Di Cecilia, L.; Rovati, L.
abstract

Hyperspectral images of the human iris, containing spectral and spatial information of the iris, are acquired by a custom developed instrument. We developed this instrument specifically to perform in-vivo spectral reflectance measurements of the human iris. The significance of the data cube acquired is strictly related to the acquisition system performance. This paper analyzes the qualitative and quantitative in-vivo performances of our instrument considering in-vivo repeatability tests and comparing left and right irises of normal subjects, without visually assessed heterochromia of the irises.


2018 - Fluorescence pH Sensor Based on Polymer Film [Relazione in Atti di Convegno]
Rovati, L; Cattini, S; Fabbri, P; Ferrari, L
abstract

Modern flexible circuit systems can include sensing elements. In this paper, possible implementation of a fluorescence pH sensor suitable for measurement of near neutral solution based on a polymer film is presented. Polymer films can satisfy the requests of the modern flexible systems, such as miniaturization, flexibility and enhanced sensitivity, allowing high performance sensing at low cost. Design, development and performance evaluation of the sensor are presented.


2018 - Imaging the human iris: a hyperspectral approach [Abstract in Rivista]
Di Cecilia, L; Marazzi, F; Rovati, L
abstract

Purpose: Hyperspectral (HS) imaging is a promising optical technique that allows the detection of both spatial and spectral information in a single data acquisition. Here we investigate the capability of a prototype HS instrument to measure the iris spectral reflectance in vivo. Moreover, we evaluate the intra- and inter-session repeatability of quantitative HS measurements of the human iris. Methods: Eight healthy volunteers (all males, average age 27 ± 2 years) participated in the study. Irises colors were classified using the grading system of Franssen et al [Grading of Iris Color with an Extended Photographic Reference Set, J Optom 2008; 1:36-40]. Each HS acquisition (duration: 4125 ms) consists of 22 images (HS cube) captured between 480 – 900 nm, in 20nm intervals. Each acquisition was repeated 6 times. The instrument was calibrated using a NIST white reflectance standard, to ensure quantitative and repeatable measurements. Reflectance was analyzed across the 22 spectral bands in an annular region of interest concentric to the pupil. Repeatability was assessed from images captured in 3 sessions, at the same exposure time, with realignment of the iris and refocusing between each session. Results: Inter-subject variability was highest at short wavelengths (Fig. 1) and reflectance exhibited opposite trends in the visible and near infrared. This might be the result of melanin scattering. The influence of water absorption is detected above 850 nm. Repeatability was highest for lighter irises and for wavelengths from 520 to 900 nm. In that range, the coefficient of repeatability (95% of confidence interval) for measurements between sessions was ±10% and ±5% for dark and light irises, respectively. The within-session repeatability was ±7.5% and ±4%, respectively. Conclusions: Automated in vivo HS imaging of the human iris appears to be reliable and reproducible. This technique could potentially be exploited for monitoring iris pigmentation changes with time induced by prostaglandin analogues. In addition, the iris spectral reflectance could be correlated with the development of certain ocular pathologies.


2018 - IOT-Based Measurement System for Wine Industry [Relazione in Atti di Convegno]
Masetti, Gianluca; Marazzi, Francesco; DI CECILIA, Luca; Rovati, Luigi
abstract

An IoT-based measurement system designed to monitor wine fermentation during vinification process is presented. The system consists in a network of sensorized buoys, placed inside the tanks where fermentation occurs, and access points used to share the data to a cloud web platform. The access to the collected data is performed by an intuitive web interface. The system architecture could provide multiple services for the farmers and winemakers, such as vinification monitoring, but also market oriented services (e.g.Traceability of the product). Preliminary experimental results demonstrated the capability of the system in measuring the wine pH, liquid level and temperature in a 24 hours interval with low uncertainty, along with the possibility to upload data on a website.


2018 - Spectral Repeatability of a Hyperspectral System for Human Iris Imaging [Relazione in Atti di Convegno]
Di Cecilia, L.; Marazzi, F.; Rovati, L.
abstract

The present study was conducted to evaluate the measuring performance of a prototype hyperspectral imaging system. This instrument was developed to measure the human iris spectral reflectance in vivo. Several previous works highlighted how changes in the iris pigmentation and morphology may provide an indication of the development and progression of certain eye pathologies. The use of hyperspectral imaging could aid physicians in the early detection of such diseases, by exploiting both the spatial and spectral features that this optical technique is able to collect. We evaluated the measurements repeatability from images acquired across 22 spectral bands in the visible and near-infrared range (480-900 nm), from 8 healthy volunteers. Moreover, we assessed the intra-and inter-session repeatability of the quantitative hyperspectral measurements. Repeatability was lower for darker irises and for wavelengths from 520 to 900nm. In particular, the coefficient of repeatability (95% of confidence interval) for measurements between sessions was ±10% and ±5% for dark and light irises, respectively. The within session repeatability was ±7.5% and ±4%, respectively. The obtained repeatability coefficients confirm the reliability and reproducibility of the hyperspectral data collected by our system.


2017 - A hyperspectral imaging system for the evaluation of the human iris spectral reflectance [Relazione in Atti di Convegno]
DI CECILIA, Luca; Marazzi, Francesco; Rovati, Luigi
abstract

According to previous studies, the measurement of the human iris pigmentation can be exploited to detect certain eye pathological conditions in their early stage. In this paper, we propose an instrument and a method to perform hyperspectral quantitative measurements of the iris spectral reflectance. The system is based on a simple imaging setup, which includes a monochrome camera mounted on a standard ophthalmic microscope movement controller, a monochromator, and a flashing LED-based slit lamp. To assure quantitative measurements, the system is properly calibrated against a NIST reflectance standard. Iris reflectance images can be obtained in the spectral range 495-795 nm with a resolution of 25 nm. Each image consists of 1280 x 1024 pixels having a spatial resolution of 18 μm. Reflectance spectra can be calculated both from discrete areas of the iris and as the average of the whole iris surface. Preliminary results suggest that hyperspectral imaging of the iris can provide much more morphological and spectral information with respect to conventional qualitative colorimetric methods.


2017 - An improved imaging system for hyperspectral analysis of the human iris [Relazione in Atti di Convegno]
Di Cecilia, Luca; Marazzi, Francesco; Rovati, Luigi
abstract

We have developed an instrument and a method to perform in vivo hyperspectral imaging of the human iris in order to quantitatively measure its spectral reflectance. Understanding age-related changes in the reflectance properties of the iris is important for multiple aspects of vision research. The images are acquired in the spectral range 450-810nm from three healthy volunteers. The spectral resolution is equal to 30nm, while each image of 1024×768 pixels has a spatial resolution of 22.5μm. The instrument appears suitable for measuring iris pigmentation changes over time. These measurements could offer new diagnostic possibilities in ophthalmology.


2017 - An improved optical scheme for self-mixing low-coherence flowmeters [Relazione in Atti di Convegno]
DI CECILIA, Luca; Rovati, Luigi; Cattini, Stefano
abstract

In this paper we present a fiber-based low-coherence self-mixing interferometer exploiting a single-arm approach to measure the flow in a pipe. The main advantages of the proposed system are the flexibility offered by fiber-connected optical head, a greater ease of alignment, the rejection of “common-mode” vibrations, and greater stability. Thanks to the use of a low-coherence source, the proposed system investigates the velocity of the scattering particles owing only in a fixed and well defined region located close to the duct wall itself. The reported experimental results demonstrate that in laminar flow regime the developed system is able to determine the flow and it is quite robust to variation in the scatterers concentration. Increasing the scatterers concentration of about 24 times, the sensitivity S has reduced of less than 30%. © (2017) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.


2017 - Effects of the density and homogeneity in NIRS crop moisture estimation [Relazione in Atti di Convegno]
Lenzini, Nicola; Rovati, Luigi; Ferrari, Luca
abstract

Near-infrared spectroscopy (NIRS) is widely used in fruits and vegetables quality evaluation. This technique is also used for the analysis of alfalfa, a crop that occupies a position of great importance in the agricultural field. In particular for the storage, moisture content is a key parameter for the crops and for this reason its monitoring is very important during the harvesting phase. Usually optical methods like NIRS are well suitable in laboratory frameworks where the specimen is properly prepared, while their application during the harvesting phase presents several diffculties. A lot of influencing factors, such as density and degree of homogeneity can affect the moisture evaluation. In this paper we present the NIRS analysis of alfalfa specimens with different values of moisture and density, as well as the obtained results. To study scattering and absorption phenomena, the forward and backward scattered light from the sample have been spectrally analyzed.


2017 - Hyperspectral imaging of the human iris [Relazione in Atti di Convegno]
Di Cecilia, Luca; Marazzi, Francesco; Rovati, Luigi
abstract

We describe an optical system and a method for measuring the human iris spectral reflectance in vivo by hyperspectral imaging analysis. It is important to monitor age-related changes in the reflectance properties of the iris as they are a prognostic factor for several eye pathologies. In this paper, we report the outcomes of our most recent research, resulting from the improvement of our imaging system. In particular, a custom tunable light source was developed: the images are now acquired in the spectral range 440-900 nm. With this system, we are able to obtain a spectral resolution of 20nm, while each image of 2048 x 1536 pixels has a spatial resolution of 10.7 μm. The results suggest that the instrument could be exploited for measuring iris pigmentation changes over time. These measurements could provide new diagnostic capabilities in ophthalmology. Further studies are required to determine the measurements' repeatability and to develop a spectral library for results evaluation and to detect differences among subsequent screenings of the same subject.


2017 - On the behavior of LED lamps under non-sinusoidal voltage conditions [Relazione in Atti di Convegno]
Peretto, Lorenzo; Tinarelli, Roberto; Rovati, Luigi; Bernabei, Mario
abstract

The diffusion of LED lamps on the market is becoming increasingly wide and it is expected that, in a few years, they become a sort of standard de facto for lighting of houses as well as offices. As a consequence, they can be considered for replacing the incandescent bulb in the international standard for flicker measurement given that, as it is well known, this last lamp is banned from the market and hence the measurement of flicker severity is no more related with the actual annoyance caused by the light fluctuation. In this connection, this paper will investigate the behavior of several same-power LED bulbs under nonsinusoidal voltage conditions to verify if it is possible to choose a specific LED source as a reference for flicker evaluation.


2017 - On the feasibility of a CENTA-based biosensor to measure antibiotics concentration in milk [Relazione in Atti di Convegno]
Ferrari, Luca; Rovati, Luigi; Costi, Maria Paola; Venturelli, Alberto; Luciani, Rosaria; Cattini, Stefano
abstract

In veterinary practice antibiotics are used and abused all over the world both to treat diseases and prevent infections and, to increase feed efficiency thus promoting growth in food producing animals. With more than 30 years history, β-lactam antibiotics are nowadays one of the most important group of antibiotics in veterinary medicine. In this paper we investigate the possibility to realize a measurement method suitable for field testing and we propose a competitive biosensor based on a relatively low-cost chromogenic cephalosporin (CENTA) for the quantitative analysis of β-lactams concentration in milk. In particular, the reported preliminary study has been focused on cloxacillin and the reported results indicates that the method is potentially able to detect cloxacillin at a concentration of about one order of magnitude lower than the maximal residue limits (MRL) set by the European Commission.


2017 - Single-arm Self-mixing Superluminescent Diode Interferometer for Flow Measurements [Articolo su rivista]
DI CECILIA, LUCA; CATTINI, Stefano; GIOVANARDI, FABIO; ROVATI, Luigi
abstract

Laser-diode self-mixing interferometry is a noncontact technique widely used both in industries and laboratories. In this paper we propose to extend the self-mixing approach to low-coherence sources such as superluminescent diodes. In particular, we present a fiber-based common-path interferometer exploiting a single mode pigtailed super-luminescent diode. The developed measuring system has been demonstrated to be able to directly measure the flow in pipes. To the best of our knowledge, it is the first time that flow measurements have been performed by a single-arm self-mixing pigtailed super-luminescent-diode. The measuring system exploits the Doppler interference pattern produced by the light back-reflected from the inner facet of the pipe wall and the light back-diffused by the moving particles. Then, the use of a low-coherence source allows to measure the velocity of the scattering particles in a fixed and well defined region located close to the pipe wall, thus providing good robustness to variations of scatterers concentration and allowing to easily estimate the flow under the laminar flow assumption. Experimental results demonstrated a high linearity (Pearson coefficient of about 99%) and sensitivity of about 16.62±1.1 cm−3, with flows ranging from 1 cm3/s to 15 cm3/s and scatterers volume concentration ranging from 0.015% to 0.36%.


2016 - A simple calibration method to quantify the effects of head movements on vision-based eye-tracking systems [Relazione in Atti di Convegno]
Cattini, Stefano; Rovati, Luigi
abstract

A simple method for the calibration of eye-tracking systems based on eye-features detection is proposed. Many eye-tracking systems are claimed to be robust to head movements in some degree, but such robustness is rarely fully quantified. Moving chin-rest and synthetic images have been proposed to investigate head movements. However, both methods have several limitations. The reported calibration method exploits for the first time ocular imaging eye models (OIEMs) in order to simulate the eye(s), thus allowing to easily investigate the effects due to head movements. Moreover, it can be useful for the development and comparison of eye-tracking hardware, software and whole systems. Differently from human subjects, OIEMs are standardized and time-invariant thus, comparisons can be performed at different times and places, leading OIEMs to be a potential gold standard test for eye-tracking systems. Preliminary verification performed on a basic eye tracking system corroborate the applicability of described method.


2016 - An Optical Technique for Real-Time Monitoring of Hemolysis During Hemodialysis [Articolo su rivista]
Cattini, Stefano; Rovati, Luigi
abstract

Hemolysis--the lysis of red blood cells (RBCs) causing the release of free hemoglobin (Hb) into the patient's blood--is an unavoidable side effect of any extracorporeal circulation. If not promptly detected, hemolysis and the consequent free Hb can lead to severe health risks for the patient, such as thrombosis, compromised oxygen-carrying capacity that may cause injury to the brain and other organs, and, ultimately, the death of the patient. Accurate measurement methods to detect Hb have been known for a long time. However, such methods generally exploit toxic chemicals and/or are unable to distinguish the deleterious free Hb from the Hb contained inside intact RBCs; thus they are unsuitable for inline monitoring of the extracorporeal circulation. In this paper, a simple measurement method and a measuring system for early detection of hemolysis in hemodialysis (HD) are described. The developed measuring system performs an optical analysis of the dialysis fluid in order to estimate the free Hb concentration in the blood returned to the patient, thus potentially allowing for the first time the real-time and in-line quantitative monitoring of hemolysis in HD. Moreover, the noncontact features of the proposed technique and its analyses of the waste of the hemodialyzer allow both overcoming several issues related to biological risk in medical devices and easy integration into hemodialyzers already in use. Only vast clinical trials may be able to reasonably provide a significant estimation of the achievable measurement uncertainty. Nevertheless, the reported preliminary ex vivo experiments show that hemolysis can be detected with resolution and sensitivity potentially sufficient to reduce risks for patients.


2016 - Measuring haemolysis in haemodialysis: Comparison between a new and existing data processing algorithms [Relazione in Atti di Convegno]
Cattini, Stefano; Rovati, Luigi
abstract

Acute haemolysis in haemodialysis is a relatively rare complication, but it can lead to life-threatening issues up to the death of the patient. Due to the lack of measurement methods able to provide a realtime and in-line measurement of the haemolysis in extracorporeal circulation, in current medical practice the haemolysis level is not monitored during haemodialysis. In last two years we proposed a measurement method capable to measure in-line and in real-time the haemolysis level during haemodialysis. Such method is based on the estimation of the filter permeability to haemoglobin. To estimate the filter permeability we proposed two data processing algorithms: one simplified algorithm supposing constant permeability and the other supposing the filter permeability to be a linear function of the time integral of the filtered volume of solvent. However, the constant permeability algorithm is reasonably prone to errors, whereas the algorithm based on the time integral of the solvent volume does not allow the integration of the developed measuring system with hemodialyzers already in use. To overcome such limitation, in this paper we propose a new data processing algorithm based on the time integral of the mass of filtered haemoglobin. Such quantity can be easily estimated by the measuring system, allowing straightforward integration with hemodialyzers already in use. The performed experimental activities indicate as the new data processing algorithm is reasonably able to provide performance equal or better than the previous data processing algorithms.


2016 - Near-infrared spectroscopy for non-invasive monitoring of drugs blood-brain barrier penetration [Relazione in Atti di Convegno]
Rovati, Luigi; Cattini, Stefano; Crespi, Francesco
abstract

In this paper, a near-infrared spectroscopy instrument adapted for in-vivo NIRS measurements of rodent's brain is presented. This prototype was designed for non-invasive analysis of the two main forms of hemoglobin: oxy-hemoglobin and deoxy-hemoglobin. These two chromophores are markers of the degree of tissue oxygenation, thus providing an index of blood levels and therefore of brain metabolism. This information can be profitably used for non-invasive monitoring the ability of drugs to penetrate the blood-brain barrier. The preliminary experimental activity denotes an original relationship between NIRS analysis of brain blood metabolism and drugs effect.


2015 - A simple measuring system and calibration method to investigate light transmission ability of light-transmitting fiber posts [Relazione in Atti di Convegno]
Cattini, Stefano; Rovati, Luigi
abstract

Light-transmitting fiber posts are recognized to potentially improve the cements polymerization, thus potentially improving the bonding of the endodontics restoration. However, different posts generally have completely different light transmission, hence it is important to be able to compare their optical performances. In this paper a simple measuring system able to compare the exitance generate by different light-transmitting fiber posts is proposed. The described measuring system is based on a microscope and a digital camera coupled to its optics. A simplified calibration and a detailed measurement procedure are described and investigated. Then, data obtained from the analysis of some commercial light-transmitting fiber posts are reported and briefly discussed. Even though, mechanical properties, biocompatibility and aesthetics have to be taken into account once choosing the post, the data provided by the proposed measuring system may support in choosing the post and, defining the proper light-source power and exposure duration.


2015 - Design and performance of an Hb measuring system: Viability of its use in a haemodialysis [Relazione in Atti di Convegno]
Cattini, Stefano; Rovati, Luigi
abstract

Haemolysis is an unavoidable side effect of any extracorporeal circulation. If not promptly detected, haemolysis can lead to severe health risks for the patient such as thrombosis, compromised oxygen-carrying capacity that may cause injury to the brain and other organs, and, ultimately, a cardiac arrest.


2015 - In vivo real time non invasive monitoring of brain penetration of chemicals with near-infrared spectroscopy: Concomitant PK/PD analysis [Articolo su rivista]
Crespi, Francesco; Cattini, Stefano; Donini, Maurizio; Bandera, Andrea; Rovati, Luigi
abstract

Background. Near-infrared spectroscopy (NIRS) is a non-invasive technique that monitors changes in oxygenation of haemoglobin. The absorption spectra of near-infrared light differ for the oxygenation–deoxygenation states of haemoglobin (oxygenate (HbO2) and deoxygenate (Hb), respectively) so that these two states can be directly monitored. Comparison with existing method(s). Different methodologies report different basal values of HbO2 and Hb absolute concentrations in brain. Here, we attempt to calculate basal HbO2 levels in rat CNS via evaluation of the influence of exogenous oxygen or exogenous carbon dioxide on the NIRS parameters measured in vivo. New method. Furthermore the possibility that changes of haemoglobin oxygenation in rat brain as measured by NIRS might be a useful index of brain penetration of chemical entities has been investigated. Different compounds from different chemical classes were selected on the basis of parallel ex vivo and in vivo pharmacokinetic (PK/PD) studies of brain penetration and overall pharmacokinetic profile. Results. It appeared that NIRS might contribute to assess brain penetration of chemical entities, i.e. significant changes in NIRS signals could be related to brain exposure, conversely the lack of significant changes in relevant NIRS parameters could be indicative of low brain exposure. Conclusions. This work is proposing a further innovation on NIRS preclinical applications i.e. a “chemical” NIRS [chNIRS] approach for determining penetration of drugs in animal brain. Therefore, chNIRS could became a non invasive methodology for studies on neurobiological processes and psychiatric diseases in preclinical but also a translational strategy from preclinical to clinical investigations.


2015 - Measurement of the pupil responses induced by RGB flickering stimuli [Relazione in Atti di Convegno]
Bernabei, Mario; Rovati, Luigi; Peretto, Lorenzo; Tinarelli, Roberto
abstract

The big changes in indoor illumination caused by the introduction of LED-based devices may have effects on the health and well-being of the persons that are still under study. From the point of view of flicker, these changes further highlight the inadequacy of the current international standard. With the aim of providing a contribution to a matter that involves several scientific disciplines, new results on pupil responses induced by RGB flickering stimuli are presentedin this paper. Tests on volunteers have been performed to evaluate the inter- and intra-subject variability of pupil responses induced by the above stimuli.An instrument formerly developed (and described in previous paper) has been usedto investigate the pupil response. The results of this extensive measurement campaign are presented and discussed.


2015 - Trap-assisted tunneling contributions to subthreshold forward current in InGaN/GaN light-emitting diodes [Relazione in Atti di Convegno]
Mandurrino, M.; Goano, M.; Dominici, S.; Vallone, M.; Bertazzi, F.; Ghione, G.; Bernabei, Mario; Rovati, Luigi; Verzellesi, Giovanni; Meneghini, M.; Meneghesso, G.; Zanoni, E.
abstract

We present results from a combined experimental and numerical investigation of trap-assisted tunneling contributions to subthreshold forward current in InGaN/GaN light-emitting diodes. We show that the excess forward leakage current in single-quantum-well InGaN/GaN light-emitting diodes can be explained by non-local tunneling-into-traps processes and subsequent non-radiative recombination with free carriers.


2014 - A simple and robust optical scheme for self-mixing low-coherence flowmeters [Relazione in Atti di Convegno]
Cattini, Stefano; Rovati, Luigi
abstract

The developed measuring system is based on a low-coherence source and a self-mixing (or inter- nal) detection. The proposed optical layout exploits the reflection from the internal wall of the duct as reference arm, thus reducing system complexity, cost, size and increasing its robustness to movements of the measurand. Moreover, the usage of a low-coherence source allows reducing the problems related to the poor definition of the volume under test (sensing region or measurement volume) typical of “coherent” self-mixing systems. Although preliminary analysis have been performed by simply investigating the frequencies rel- ative to the maximum in the Doppler spectrum, the obtained results demonstrates that by in- creasing scatterers concentration of +300%, the system sensitivity increases of about only +20%.


2014 - A simple handheld pupillometer for chromatic Flicker studies [Relazione in Atti di Convegno]
Fabrice, Manns; Per G., Söderberg; Arthur, Ho; M., Bernabei; R., Tinarelli; L., Peretto; Rovati, Luigi
abstract

A portable pupillometer has been developed which is capable of performing accurate measurements of the pupil diameter during chromatic flicker stimulations. The handheld measuring system records the near-infrared image of the pupil at the rate of 25 fps and simultaneously stimulates the eye using a diffused flicker light generated by light emitting diodes (LEDs). Intensity, frequency and chromatic coordinates of the stimulus can be easily adjusted using a user-friendly graphical interface. Thanks to a chromatic monitoring of the stimulus close to the plane of the eye, photopically matched conditions can be easily achieved. The pupil diameter/area can be measured during flickering stimuli that are generated with frequency in a range of 0.1-20 Hz. The electronic unit, properly connected to the personal computer through a USB port, drives the optical unit, which can be easily held in a hand. The software interface controlling the system was developed in LabVIEW. This paper describes the instrument optical setup, front-end electronics and data processing. Moreover preliminary results obtained on a voluntary are reported. © (2014) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.


2014 - A simple measuring system for early detection of haemolysis during haemodialysis [Relazione in Atti di Convegno]
Cattini, Stefano; Rovati, Luigi; M., Bernabei; D., Cianciavicchia; P., Monari; A., Sicuri
abstract

A simple measuring system for early detection of haemolysis during haemodialysis is proposed. The developed measuring system performs an optical absorption spectroscopy analysis of the dialysis fluid in order to estimate the free haemoglobin concentration in the blood returned to the patient-the potential cause of injury for the patient. The integration of the developed measuring system into hemodialyzers results simple and relatively inexpensive (overall system cost is about few hundred dollars). Preliminary results confirm the applicability of the proposed measuring system.


2014 - A simple portable polychromatic pupillometer for human eye annoyance measurement [Relazione in Atti di Convegno]
Mario, Bernabei; Rovati, Luigi; Lorenzo, Peretto; Roberto, Tinarelli
abstract

The Standards EN 61000-4-15 which has been adopted by the IEEE as IEEE std 1453, gives functional and design specifications about the actual Flickermeter based on the analysis of the voltage supplying a specified light source. Such incandescent light source based instrument is obsolete nowadays, with the advent of new light sources, such as halogen, fluorescent, and especially solid state sources; a different and appropriate tools is mandatory to investigate the effects on the human eye of these sources. This paper describes an improved version of the instrument presented in our previous articles. Thanks to a microcontroller, the new system allows controlling all the characteristics of the flicker stimulus, i.e. amplitude, mean value, modulation, frequency and color. Moreover, the optical head has been revised in order to improve the alignment repeatability.


2014 - An in vitro model of a system of electrical potential compensation in extracorporeal circulation. [Articolo su rivista]
Carletti, U.; Cattini, Stefano; Lodi, Renzo; Petralia, A.; Rovati, Luigi; Zaffe, Davide
abstract

OBJECTIVES: Extracorporeal circulation (ECC) in patients undergoing cardiac surgery induces systemic immune-inflammatory reaction that results in increased postoperative morbidity. Many factors are responsible for the adverse response after ECC. The present in vitro study aimed to investigate electric charges (ECs) generated during ECC, to set a device compensating the ECs, and checking its effect on red blood cells (RBC).; MATERIALS AND METHODS: The electrical signals of blood in ECC were collected by a custom developed low-noise electronic circuit, processed by a digital oscilloscope (DSO) and a dynamic signal analyzer (DSA). The compensation of ECs was performed using a compensation device, injecting a nulling charge into the blood circuit. The compensation effect of the ECs on RBCs was evaluated by scanning electron microscope (SEM).; RESULTS: The electrical analysis performed using both the DSO and the DSA confirmed the EC formation during ECC. The notable electric signals recorded in standard ECC circuits substantially nulled once the compensation device was used, thus confirming efficient EC compensation. After two hours of ECC, the SEM non-blended test on human RBC samples highlighted morphological changes in acanthocytes of the normal biconcave-shaped RBC.; CONCLUSIONS: The outcomes confirm the development of parasitic ECs during ECC and that a suppressor system may decrease the potential damage of ECs. Nevertheless, further studies are ongoing in order to investigate the complex mechanisms related to lymphocytes and platelet morphological and physiological chances during triboelectric charges in ECC.


2014 - Highly stable plastic optical fibre amplifiers containing [Eu(btfa)3(MeOH)(bpeta)]: A luminophore able to drive the synthesis of polyisocyanates [Articolo su rivista]
P., Fabbri; S., Mohammad Poor; L., Ferrari; Rovati, Luigi; S., Borsacchi; M., Geppi; P. P., Lima; L. D., Carlos
abstract

The rare-earth metal organic chelate [Eu(btfa)3(MeOH)(bpeta)] (btfa, 4,4,4-trifluoro-1-phenyl-1,3-butanedionate; bpeta, 1,2-bis(4-pyridyl)ethane) has been used to dope a plastic optical fibre (POF) prepared by the bulk homopolymerization of hexamethylene diisocyanate (HMDI) catalysed by Tin(II)-2 ethylhexanoate (SnOct), to obtain a plastic optical fibre amplifier (POFA). The Eu3+ chelate, primarily added as luminophore for the amplification of the optical signal, showed an interesting co-catalytic activity in the polymerization of HMDI, that preferentially proceeded towards the formation of the highly stable polyisocyanurate trimer form thanks to its selective driving action, as demonstrated by 13C solid-state NMR. Pumping of the POFA with xenon lamps demonstrated the occurrence of stimulated emission inside the doped fibre.


2014 - On-line pH measurements of near-neutral solutions by a disposable polymer based probe [Relazione in Atti di Convegno]
Luca, Ferrari; Rovati, Luigi; Fabbri, Paola; Pilati, Francesco
abstract

An on-line optical pH sensor for the measurement of near-neutral solutions is presented. It consists of a disposable polymeric probe, encapsulating the fluorescein O-methacrylate 97 %, which is used as the indicator. The interrogation of the sensing element and the collection of the signal of interest is performed trough the use of an ad hoc optical head. Finally, a driver, front-end and signal processing electronics has been designed and realized to acquire and process the information of interest.


2013 - Continuous haematic pH monitoring in extracorporeal circulation using a disposable florescence sensing element. [Articolo su rivista]
Ferrari, L; Rovati, Luigi; Fabbri, Paola; Pilati, F.
abstract

During extracorporeal circulation (ECC), blood is periodically sampled and analyzed to maintain the blood-gas status of the patient within acceptable limits. This protocol has well-known drawbacks that may be overcome by continuous monitoring. We present the characterization of a new pH sensor for continuous monitoring in ECC. This monitoring device includes a disposable fluorescence-sensing element directly in contact with the blood, whose fluorescence intensity is strictly related to the pH of the blood. In vitro experiments show no significant difference between the blood gas analyzer values and the sensor readings; after proper calibration, it gives a correlation of R>0.9887, and measuring errors were lower than the 3% of the pH range of interest (RoI) with respect to a commercial blood gas analyzer. This performance has been confirmed also by simulating a moderate ipothermia condition, i.e., blood temperature 32°C, frequently used in cardiac surgery. In ex vivo experiments, performed with animal models, the sensor is continuously operated in an extracorporeal undiluted blood stream for a maximum of 11 h. It gives a correlation of R>0.9431, and a measuring error lower than the 3% of the pH RoI with respect to laboratory techniques.


2013 - Development of a Sensor System for the Determination of Sanitary Quality of Grapes. [Articolo su rivista]
Zanardi, Chiara; Ferrari, Luca; Zanfrognini, Barbara; Pigani, Laura; Terzi, Fabio; Cattini, Stefano; Rovati, Luigi; Seeber, Renato
abstract

An instrument for the automatic quantification of glycerol in grapes has been developed. We verify here that this analyte can be taken as a benchmark of a serious disease affecting the grapevines, namely Botrytis cinerea. The core of the instrument is an amperometric biosensor consisting of a disposable screen printed electrode, generating the analytical signal thanks to a bi-enzymatic process involving glycerol dehydrogenase and diaphorase. The full automation of the analysis is realised by three micropumps and a microprocessor under control of a personal computer. The pumps allow the correct and constant dilution of the grape juice with a buffer solution also containing [Fe(CN)6]4- redox mediator and the injection of NAD+ cofactor when the baseline signal reaches a steady state; the instrument leads to automated reading of the analytical signal and the consequent data treatment. Although the analytical method is based on an amperometric technique that, owing to heavy matrix effects, usually requires an internal calibration, the analyses indicate that a unique external calibration is suitable for giving accurate responses for any grapes, both white and black ones.


2013 - Disposable Fluorescence Optical pH Sensor for Near Neutral Solutions [Articolo su rivista]
Luca, Ferrari; Rovati, Luigi; Fabbri, Paola; Pilati, Francesco
abstract

The design, development and performance evaluation of a fluorescence-based pH sensor for on-line measurements is presented. The pKa of the sensing element has been calculated to be 7.9, thus the sensor is suitable for measurement of near neutral solutions. The sensor consists of a low-cost disposable polymer sensing probe, in contact with the solution under test, interrogated by an optoelectronic transduction system. The pH sensitive dye is based on fluorescein O-methacrylate, which has been covalently linked to a hydrogel matrix, realized through the use of HEMA (2-hydroxyethyl methacrylate), HDDA (1,6-hexanediol diacrylate) and PEGDA (polyethylene glycol diacrylate). The optical interrogation setup, together with the electronics, has been developed to acquire and process the fluorescence signal. The sensor works over a pH range between 6.5 and 9.0. In the range between 7.0 and 8.0, the sensor shows a linear behavior with a maximum linearity error of 5%. Thanks to the good performance of the sensing element and transduction system, the short term drift of the reading (measured over 40 min) is lower than 0.15%. The measuring system also exhibits good performance in terms of response time and reproducibility.


2013 - Does pupil dilation influence subfoveal choroidal laser Doppler flowmetry? [Articolo su rivista]
Nithiyanantham, Palanisamy; Charles E., Riva; Rovati, Luigi; Mauro, Cellini; Corrado, Gizzi; Ernesto, Strobbe
abstract

Purpose:  The aim of this study was to assess (i) whether pupil dilation with tropicamide influences subfoveal choroidal blood flow, as assessed by continuous laser Doppler flowmetry (LDF) and (ii) if this is the case, whether the effect is due to a haemodynamic response of the drug-induced dilation. Methods:  Following the instillation of one drop of 1% tropicamide in one eye of 18 healthy, nonsmoking volunteers (age 20–25 years), the subfoveal choroidal LDF parameters (Vel, Vol and ChBF) were recorded during 30 min, at 3-min intervals under two paradigms: through an artificial pupil (4 mm diameter) placed in front of the cornea (P1) and without this artificial pupil (P2). Results:  Tropicamide increased the pupil diameter from 3.3 ± 0.4 mm (mean ± SD) to 8.3 ± 0.4 mm. Full dilation was reached at ∼24 min. During this period of time, linear regression analysis demonstrated that none of the LDF parameters varied significantly (p > 0.05), either under P1 or P2. Based on a group of 12 subjects, the smallest (%) change in the mean value of ChBF (ChBFm) that would be detectable (sensitivity of the method, S) was found to be 2% for P1 and 6% for P2. The average coefficient of variation of ChBFm based on eight measurements during dilation was greater for P2 than for P1 by a factor of approximately 2. Conclusion:  Tropicamide had no significant influence on the subfoveal choroidal LDF parameters measured by continuous LDF during pupil dilation. Furthermore, pupil dilation did not affect ChBFm by more than the calculated minimum percentage change of 6% detectable with our method.


2013 - Functional test of a Radon sensor based on a high-resistivity-silicon BJT detector [Articolo su rivista]
G. F., Dalla Betta; V., Tyzhnevyi; A., Bosi; Bonaiuti, Matteo; C., Angelini; G., Batignani; S., Bettarini; F., Bosi; F., Forti; M. A., Giorgi; F., Morsani; E., Paoloni; G., Rizzo; J., Walsh; A., Lusiani; R., Ciolini; G., Curzio; F., D'Errico; A., Del Gratta; Bidinelli, Luca; Rovati, Luigi; Saguatti, Davide; Verzellesi, Giovanni; L., Bosisio; I., Rachevskaia; M., Boscardin; G., Giacomini; A., Picciotto; C., Piemonte; N., Zorzi; M., Calamosca; S., Penzo; F., Cardellini
abstract

A battery-powered, wireless Radon sensor has been designed and realized using a BJT, fabricated on a high-resistivity-silicon substrate, as a radiation detector. Radon daughters are electrostatically collected on the detector surface. Thanks to the BJT internal amplification, real-time a particle detection is possible using simple readout electronics, which records the particle arrival time and charge. Functional tests at known Radon concentrations, demonstrated a sensitivity up to 4.9 cph/(100 Bq/m3) and a count rate of 0.05 cph at nominally-zero Radon concentration.


2013 - In vivo diffuse correlation spectroscopy investigation of the ocular fundus [Articolo su rivista]
Cattini, Stefano; Staurenghi, Giovanni; Gatti, Antonietta; Rovati, Luigi
abstract

Diffuse correlation spectroscopy (DCS) measurements in vivo recorded from rabbits' ocular fundus are presented. Despite the complexity of these ocular tissues, we provide a clear and simple demonstration of the DCS abilities to analyze variations in physiological quantities of clinical interest. Indeed, the reported experimental activities demonstrate that DCS can reveal both choroidal-flow and temperature variations and detect nano- and microaggregates in ocular fundus circulation. Such abilities can be of great interest both in fundamental research and practical clinical applications. The proposed measuring system can be useful in: (a) monitoring choroidal blood flow variations, (b) determining the end-point for photo-dynamic therapy and transpupillary thermo therapy and, (c) managing the dye injection and determining an end-point for dye-enhanced photothrombosis. Moreover, it could allow both diagnoses when the presence of nano- and micro-aggregates is related to specific diseases and verifying the effects of nanoparticle injection in nanomedicine. Even though the reported results demonstrate the applicability of DCS to investigate ocular fundus, a detailed and accurate investigation of the limits of detection is beyond the scope of this article. © 2013 Society of Photo-Optical Instrumentation Engineers.


2012 - A Novel Method for Noninvasive Monitoring of Ocular Fundus Status During Transpupillary Thermotherapy Treatment [Articolo su rivista]
Cattini, Stefano; Rovati, Luigi
abstract

A novel optical method for noninvasive monitoring of the ocular fundus status is presented. The method could provide an optimal end-point for transpupillary thermotherapy treatment, thus overcoming the severe over- and under-treatment issues currently affecting about 10% of patients. The developed instrument and measurement procedure have been tested on both a mechanical eye model and animal models. The presented results demonstrate the ability of our system to potentially detect variations in both blood flow and optical properties. Much more work will be needed before the developed instrument will be ready for clinical test, nevertheless the proposed method may provide an important improvement in the treatment of several disabling ocular diseases.


2012 - A simple measuring system for automotive damper wear estimation [Relazione in Atti di Convegno]
L., Ferrari; Cattini, Stefano; Rovati, Luigi; A., Bosi
abstract

A low-cost, portable and easy to use measuring system for the diagnosis of worn automotive dampers is proposed. The system is composed by two wireless sensing nodes equipped with MEMS accelerometers. The aim is to provide a measuring system which will yield comparable metrological performances, at a much lower cost than pre-existing systems.


2012 - Does tropicamide affect choroidal blood flow in humans? a laser Doppler flowmetry study [Relazione in Atti di Convegno]
N., Palanisamy; Rovati, Luigi; Charles E., Riva; M., Cellini; C., Gizzi; E., Strobbe; E. C., Campos
abstract

The measurement of blood flow in the ocular fundus is of scientific and clinical interest. Investigating ocular blood flow in the choroid may be important to understand the pathogenesis of numerous ocular diseases, such as glaucoma or agerelated macular degeneration (AMD). Laser Doppler flowmetry (LDF) was applied to measure relative velocity, volume and flux of red blood cells in the tissues of human eye. Its main application lies in the possibility of assessing alterations in blood flow early in the course of diseases. The purpose of the present study was to investigate the effect of pupil dilatation with one drop of 1% tropicamide on blood flow in the foveal region of the choroid of the human fundus. The blood flow parameters were measured in 24 eyes during 30 minutes (one measurement in every 3 minutes) after the application of the drop. Since the Doppler parameters depend on the scattering geometry, which may change as the pupil dilates; an artificial pupil of 4mm in diameter was placed directly in front the eye. Following the administration of tropicamide the mean pupil diameter was increased from 3.29 mm to 8.25 mm (P<0.0001, Paired student t-test). In comparison to the baseline values, the data shows no significant increases were observed in velocity, volume, and flow with 4 mm artificial pupil (0.2%, 1.3%, 0.8% respectively) and a statistically significant increases were observed without artificial pupil (10.7%, 13.9%, 12.8% respectively) following the application of tropicamide.


2012 - Haematic pH sensor for extracorporeal circulation [Relazione in Atti di Convegno]
Ferrari, Luca; Fabbri, Paola; Rovati, Luigi; Pilati, Francesco
abstract

The design and realization of an optical sensor for measuring haematic pH during extracorporeal circulation is presented. It consists of a chemical sensing element in contact with the blood, an interrogation optical head to externally probe the sensing element and the front-end electronics to acquire and process the information of interest. The fluorescein O-methacrylate 97% is used as the indicator. The developed system has been tested in-vitro and on an in-vivo animal model. It showed a linear behavior in the haematic range of interest with a mean error lower than 0.01 units of pH.


2012 - Innovative ophthalmic instrument to detect nano- and micro-aggregates in blood circulation [Relazione in Atti di Convegno]
Rovati, Luigi; Cattini, Stefano; Salvatori, Roberta; Antonietta, Gatti
abstract

An ophthalmic instrument for innovative analyses of the eye microcirculation is presented. The developed system employs a laser source to performs the DWS (diffusing-wave-spectroscopy) analysis of the light intensity back diffused by the ocular fundus structures, thus allowing a noninvasive detection of changes and modulations of both optical and dynamical properties of blood flow. The reported preliminary experimental results recorded in-vivo on rabbits' ocular fundus, demonstrate the ability of the system to detect nano- micro-aggregates carried by the blood flow in the ocular fundus.


2012 - Low-Cost Imaging Photometer and Calibration Method for Road Tunnel Lighting [Articolo su rivista]
Cattini, Stefano; Rovati, Luigi
abstract

A camera-based measuring instrument for road tunnels lighting is proposed. The system is aimed at estimating the veiling luminance as it will be perceived by a driver approaching the tunnel, thus allowing the estimation of the optimum luminance level of tunnel entrances, hence increasing the driver's safety. The proposed measuring instrument and the relative calibration method are based on a low-cost commercial grade camera and a reference standard, respectively.


2012 - Optical sensor for extracorporeal blood flow measurement [Relazione in Atti di Convegno]
M., Norgia; A., Pesatori; ROVATI, Luigi
abstract

This work describes the design and realization of an optical sensor for measuring extracorporeal blood flow. The instrument is realized by means of a self-mixing interferometer and a dedicated data elaboration system, developed by means of a numerical simulator of the blood optical scattering.


2012 - Performance of a Radon Sensor Based on a BJT Detector on High-Resistivity Silicon [Relazione in Atti di Convegno]
A., Bosi; Bidinelli, Luca; Saguatti, Davide; G. F., Dalla Betta; V., Tyzhnevyi; Rovati, Luigi; Verzellesi, Giovanni; G., Batignani; S., Bettarini; F., Forti; F., D'Errico; A., Del Gratta; L., Bosisio; I., Rachevskaia; M., Boscardin; G., Giacomini; M., Calamosca; S., Penzo; F., Cardellini
abstract

An autonomous Radon sensor with wireless connectivity has been developed, using a BJT detector on high-resistivity silicon as alpha-particle detector. Charged Radon daughters are collected on the detector surface electrostatically. Thanks to the BJT internal amplification, real-time alpha particle detection is made possible using a very simple readout electronics which records alpha-particle arrival time and charge. Functional tests at known Radon concentrations demonstrated a sensitivity up to 4.9 cph/(100 Bq/m3), which translates into the capability of detecting a Radon concentration of 200±20 Bq/m3 and 500±50 Bq/m3 after 10 and 4 h, respectively. The count rate at nominally-zero Radon concentration was 0.05 cph.


2012 - Photobleaching effects in organic thin film sensing probes [Relazione in Atti di Convegno]
L., Ferrari; Rovati, Luigi; P., Fabbri; F., Pilati
abstract

The phenomenon of photobleaching of fluorescence indicators in organic thin films is presented. The study is performed on the fluorescein methacrylate indicator immobilized in an acrylate matrix. A LED based interrogation setup has been realized to evaluate the effects of photobleaching. The experimental results show as stability and drift of the fluorescence signal induced by photobleaching are the most critical aspects in sensing applications.


2012 - Plastic Optical Fiber pH Sensor Using a Sol-Gel Sensing Matrix [Capitolo/Saggio]
ROVATI, Luigi; FABBRI, Paola; L., Ferrari; PILATI, Francesco
abstract

Current trends in optical sensors, such as miniaturization, flexibility and enhanced sensitivity, are indicating a new chemical route for the development of advanced multifunctional materials for optical applications. Those chemical technologies, which can be more easily customized and allows the inclusion of multiple functionalities within a unique preparation step, are bound to be progressively more and more applied to the preparation of optical materials.In this perspective, the sol-gel technology certainly represents one of the most promising chemical strategies, thanks to numerous advantages mainly related to simplicity and mild operative conditions. It enables creating a glass-like porous structure at room temperature by a two-step acid or base catalyzed reaction involving hydrolysis and condensation, starting with metal alkoxides M(OR)4, which transforms into a rigid three-dimensional metal-oxide network (Brinker, 1990). The sol–gel process has been proved to be flexible enough for an efficient incorporation of organic polymer chains that can behave as flexible links between the metal-oxide domains in the inorganic network, in particular when they are bearing reactive groups that can be involved in the hydrolysis–condensation reactions. The resulting materials are known as organic–inorganic hybrids (Schmidt, 2000), also commonly designated as ceramers due to the combination of the properties of ceramics (high modulus, thermal stability and low coefficient of thermal expansion) with those of organic polymers (high ductility, molecular flexibility and low temperature processing). These materials are often also known as phase-interconnected nanocomposites because of the high level of interconnection between the two phases with domain phase sizes approaching the nanometer scale. Ceramers have a huge potential for application in a variety of advanced technologies (Eckert, 2001; Sanchez, 2011; Kickelkick, 2006), both as structural materials and functional materials, such as catalyst supports, protective coatings (Messori, 2003, 2004a); Toselli, 2007; Fabbri, 2008), sensors (Rovati, 2011; Fabbri, 2011), and active glasses.Optical fiber sensors are traditionally obtain by fully-inorganic sol-gel process that allows the creation of Si-O-Si linkages between the silica core of the optical fiber and the silica porous matrix deriving from the jellification of the sensitive dye-doped colloidal suspension (Cao, 2005). However, this approach cannot be easily applied in the case of plastic optical fibers, due to the ineffective interaction between the organic PMMA optical fiber core (Lin, 2000).The approach proposed in this work consists in the fabrication of a pH sensor based on an organic-inorganic hybrid matrix obtained by a sol-gel process, doped with a pH sensitive indicator, to be applied at the tip of plastic optical fibers. Inside the sensitive element, the organic part of the hybrid glass, polyethylene oxide (PEO), plays a multiple role: (i) it allows good adhesion between the plastic optical fiber and the whole sensitive element; (ii) its weak hydrophilicity permits to tune the kinetic of response of the sensor by influencing thediffusion rate of the analyte inside the porous matrix and its interaction with the indicator; (iii) its nature of organic compound allows better physical and chemical interactions with the organic pH indicator dispersed in the hybrid matrix, thus reducing problems of leaching and enhancing the response rate of the sensor.


2012 - Self-Mixing Laser Doppler Spectra of Extracorporeal Blood Flow: A Theoretical and Experimental Study [Articolo su rivista]
M., Norgia; A., Pesatori; Rovati, Luigi
abstract

Theoretical and experimental analysis of the spectral characteristics of the signal acquired from self-mixing laser Doppler of extracorporeal blood flow is presented. The theoretical spectrum of the predetected signal is calculated in the single scattering approximation and assuming a parabolic velocity profile in the duct. The resulting signal is mixed in a diode laser cavity to generate the sensor output. Theoretical predictions are verified by measurements performed on blood and phantoms flowing in an extracorporeal circulation system.


2012 - Toward the development of a low-cost laser Doppler module for ophthalmic microscopes [Relazione in Atti di Convegno]
Cattini, Stefano; Rovati, Luigi
abstract

A laser Doppler module easily integrated into a commercial ophthalmic microscope is proposed. Such setup adds flow measurement capability to standard visual inspection of the fundus. The proposed instrument may provide important clinical information such as the detection of vessel occlusion provided by surgical treatments (i.e. photocoagulation). The measuring system is based on a self-mixing laser diode Doppler flowmeter (SM-DF). Reduced costs, easy implementation and small size represent the main features of SM-DF. Moreover, this technique offers the advantage to have the excitation and measurement beams spatially overlapped, thus both overcoming the alignment difficulty of traditional laser Doppler flowmeter and, well fitting with to limited optical aperture of the pupil. Thanks to an on-board DSP-microcontroller, the optoelectronic module directly estimates the blood flow; USB connection and an ad-hoc developed user-friendly software interface allow displaying the result on a personal computer. Preliminary test demonstrates the applicability of the proposed measuring system.


2012 - Zero-Field Readout Electronics for Planar Fluxgate Sensors Without Compensation Coil [Articolo su rivista]
Rovati, Luigi; Cattini, Stefano
abstract

A simple and sensitive readout electronics for planar fluxgate sensors is presented. The system exploits the sense coils to directly generate the compensation static field avoiding the additional coil/s required in standard closed loop configuration, thus providing clear advantages in terms of size and cost. Moreover, feedback configurations are known to provide better linearity and stability of the system. The sensitivity of the developed demonstration system can be easily set from 13.3 to 104.9 mV/μT with nonlinearity ranging from 0.17% to 0.38% of the measuring interval, whereas the corresponding measuring intervals vary from ±301 to ±38 μT. The measuring uncertainty, the noise field spectral density, and the system bandwidth have been estimated in 12.2 nT, ≈ 10 nT/√{Hz}, and ≈1.5 Hz, respectively. The proposed measuring instrument is extremely easy to use and versatile. Moreover, due to the use of commercially available ferromagnetic material and the simple and via-less design, the proposed fluxgate sensor results in a very low cost and reliable device.


2011 - A low-cost system and calibration method for veiling luminance measurement [Relazione in Atti di Convegno]
Cattini, Stefano; Grana, Costantino; Cucchiara, Rita; Rovati, Luigi
abstract

A CCD-based measuring instrument aimed at the veiling luminance estimation and the relative low-cost calibration method are described. The system may allow the estimation of the optimum luminance levels in road-tunnels lighting, thus both increasing the drivers safety and avoiding energy wasting hence unjustified higher lighting-costs.


2011 - An optical method for the analysis of the exitance diffused by light-transmitting fiber post [Relazione in Atti di Convegno]
Cattini, Stefano; Rovati, Luigi
abstract

The paper is focused on the description of a measurement procedure and image analysis technique able to easily estimate the exitance diffused by light-transmitting posts. The exitance has been measured by making use of a digital colour camera (DP20, Olympus) coupled to the optics of a microscope (SZX12, Olympus). Posts have been illuminated by using: a blue LED source (LS-450 Blue LED, Ocean Optics) with emission peak close to camphorquinone activator peak, an optical fibre and an ad-hoc realized post holder. The obtained results demonstrate that different translucent posts give rise to different exitance profiles, thus allowing to reach different polymerization depths along the post, providing different polymerization performances and, requiring different source powers and exposure times. Even though, other factors such us mechanical performances, biocompatibility and aesthetics have to be consider once choosing the more suitable post, the reported measurement procedure and data may help both in choosing the proper post and defining the optimum light-source power and exposure time.


2011 - Assessment of human annoyance under flicker condition [Relazione in Atti di Convegno]
M. G., Masi; L., Peretto; R., Tinarelli; Rovati, Luigi
abstract

The international standard EN 61000-4-15 gives functional and design specifications for the Flickermeter currently used to evaluate the flicker severity, as defined in the International Electrotechnical Vocabulary. That instrument doesn't work properly if light sources different than incandescent-filament one are considered. This paper is aimed at presenting a step towards an innovative Flickermeter which is able to account a larger variety of luminous sources. In particular, the goal of this study is to find a new method to define the human annoyance under flicker condition, based on the measurement of the pupil size in presence of different flicker stimuli. The design and characterization of an automatic system able to generate flicker and measure the pupil size will be presented. In addition, the results obtained on human subject will be illustrated.


2011 - BJT detector with FPGA-based read-out for alpha particle monitoring [Articolo su rivista]
V., Tyzhnevyi; G. F., Dalla Betta; Rovati, Luigi; Verzellesi, Giovanni; N., Zorzi
abstract

In this work we introduce a new prototype of readout electronics (ALPHADET), which was designed for an a-particle detection system based on a bipolar junction transistor (BJT) detector. The system uses an FPGA, which provides many advantages at the stage of prototyping and testing the detector. The main design and electrical features of the board are discussed in this paper, along with selected results from the characterization of ALPHADET coupled to BJT detectors.


2011 - Construction and evaluation of a disposable pH sensor based on a large core plastic optical fiber [Articolo su rivista]
Rovati, Luigi; Fabbri, Paola; Luca, Ferrari; Francesco, Pilati
abstract

The fabrication and characterization of a disposable optical fiber sensor for the detection of pH in the range 5-8 are described. The sensing element is a drop of sol-gel hybrid material containing phenol red and deposited onto the tip of a large core plastic optical fiber. This fiber is also exploited for the optical interrogation. This probe can be used as a disposable part of a measuring system. The dynamic range and temporal response of the sensor are here investigated.


2011 - Dispositivo e metodologia per la misura di concentrazione di gas radon [Brevetto]
Bidinelli, Luca; Bonaiuti, Matteo; Bosi, Andrea; DALLA BETTA GIAN, Franco; Rovati, Luigi; Saguatti, Davide; Verzellesi, Giovanni
abstract

Un dispositivo di misura della concentrazione di gas Radon comprende una camera di misura (20) dotata di un dispositivo rivelatore (23), atto a rivelare particelle alfa da gas Radon; il dispositivo dell’invenzione comprende inoltre un elettrodo di raccolta (22) esterno alla camera di misura(20), atto a raccogliere i prodotti di decadimento del Radon elettricamente carichi provenienti dalla camera di misura (20).Un’unità di controllo (30) temporizza il passaggio tra due fasi operative (I, II) in cui il dispositivo rivelatore (23) e l’elettrodo di raccolta (22) sono attivi non contemporaneamente. [FIG. 1]


2011 - Effect of timolol on sub-foveal choroidal blood flow using laser Doppler flowmetry [Relazione in Atti di Convegno]
Nithiyanantham, Palanisamy; Rovati, Luigi; Mauro, Cellini; Corrado, Gizzi; Ernesto, Strobbe; Emilio, Campos; Charles E., Riva
abstract

Laser Doppler flowmetry (LDF) is a technique used to measure relative average velocity, number and flux (number times velocity) of red blood cells in vessels or capillaries. In this study, the effect of topical timolol on the choroidal circulation was investigated in 12 healthy subjects. Maximum velocity of red blood cells and volumetric blood flow rate in sub-foveal choroids are determined in each eye just before instillation of drops and then every 30 min upto 2 hours. Average intraocular pressure (IOP) decreased significantly in the timolol-treated eyes compared to that of placebo-treated eyes. Nevertheless no significant differences in choroidal blood hemodynamic between timolol and placebo-treated eyes were observed.


2011 - Measurement of the fluid-velocity profile using a self-mixing superluminescent diode [Articolo su rivista]
Rovati, Luigi; Cattini, Stefano; Palanisamy, Nithiyanantham
abstract

A novel optical Doppler velocimeter using a self-mixing superluminescent diode is proposedand demonstrated. The operation mechanism uses the photodiode on the back-face of acommercial superluminescent diode to detect the Doppler signal from an interferometer.Thanks to the low coherence length of the optical source, the position of the measuring volumecan be easily moved into the sample under test by adjusting the reference arm length, thusallowing us to measure the velocity profile of the flowing scatterers even in turbid media. Theproposed velocimeter is expected to have several industrial as well as medical applications.


2011 - Photon correlation spectroscopy in ophthalmology [Relazione in Atti di Convegno]
Rovati, Luigi
abstract

On the basis of the theory of light scattering, photon correlation spectroscopy has been used for more than three decades to study ocular tissues. From first in-vitro experiments to study cataractogenesis, this approach has been extended to characterize semi-quantitatively in-vivo all the ocular tissues from cornea to retina and choroids. In order to acquire high quality measurement data from the experiments, serious attention has to be paid to the detector and processing system performance. Detector noise, sensitivity, dead time and afterpulsing lead to a direct or indirect corruption of the acquired correlation function whereas counting range and resolution should be optimized to take into account the wide variability of the ocular tissue optical characteristics.


2011 - Poly(ethylene oxide)–silica hybrids entrapping sensitive dyes for biomedical optical pH sensors: Molecular dynamics and optical response [Articolo su rivista]
Fabbri, Paola; Pilati, Francesco; Rovati, Luigi; Ruel, Mckenzie; J., Mijovic
abstract

Polymer–silica hybrid nanocomposites prepared by sol–gel process based on triethoxisilane-terminatedpoly(ethylene oxide) chains and tetraethoxysilane as silica precursor, doped with organic pH sensitivedyes, have been prepared and their suitability for use as sensors coupled with plastic optic fibers has beenevaluated. Sensors were prepared by immobilizing a drop of the hybrid materials onto the tip of a multimodepoly(methyl methacrylate) optical fiber. The performance of the optical sensor in terms of sensitivityand response time was tested in different experimental conditions, and was found to be markedlyhigher than analogous sensors present on the market. The very fast kinetic of the hybrid’s opticalresponse was supported by studies performed at the molecular level by broadband dielectric relaxationspectroscopy (DRS), investigated over a wide range of frequency and temperature, showing that poly(ethyleneoxide) chains maintain their dynamics even when covalently bonded to silica domains, whichdecrease the self-association interactions and promote motions of polymer chain segments. Due to thefast response kinetic observed, these pH optical sensors result suitable for the fast-detection of biomedicalparameters, i.e. fast esophageous pH-metry.


2011 - Sensori per la rivelazione del Radon [Spin Off]
Rovati, Luigi; Verzellesi, Giovanni; Gian franco Della, Betta; Luca, Bidinelli; Davide, Saguatti; Andrea, Bosi; Matteo, Bonaiuti
abstract


2010 - A 2.4-GHz wireless alpha-ray sensor for remote monitoring and spectroscopy [Relazione in Atti di Convegno]
Rovati, Luigi; Verzellesi, Giovanni; Bonaiuti, Matteo; Bidinelli, Luca; Saguatti, Davide; G. F., Dalla Betta; V., Tyzhnevyi; N., Zorzi; S., Bettarini
abstract

Wireless alpha-ray device has been designed, realizedand tested in operation. The first prototype is a battery-suppliedsystem with a compact package and wireless communicationcapability. One of the more attractive features is its ability tooperate in a star network (single point-to-multipoint). The sensorrecords the arrival time of the alpha particles and the spectrumof the produced charge; it transmits this information in regulartime intervals or upon request to the base station. The overallsystem has a compact package suitable for remote alpha-rayspectroscopy.


2010 - An attempt to understand flicker vertigo: changes in pupil size and choroidal blood flow under flickering conditions [Relazione in Atti di Convegno]
Maria Gabriella, Masi; Lorenzo, Peretto; Rovati, Luigi; Rafat R., Ansari
abstract

Light flickering at a rate of 4- 20 cycles per second can produce unpleasant reactions such as nausea and vertigo. In this paper, the possibility of achieving an objective evaluation/prediction of the physiological effects induced by flicker is investigated using a new imaging method based on the pupil size determination. This method is also compared with the blood flow analysis in the choroid.


2010 - Blood flow measurement in extracorporeal circulation using self-mixing laser diode [Relazione in Atti di Convegno]
Cattini, Stefano; Michele, Norgia; Alessandro, Pesatori; Rovati, Luigi
abstract

To measure blood flow rate in ex-vivo circulation, we propose an optical Doppler flowmeter based on the self-mixing effect within a laser diode (SM-LD). Advantages in adopting SM-LD techniques derive from reduced costs, ease of implementation and limited size. Moreover, the provided contactless sensing allows sensor reuse, hence further cost reduction. Preliminary measurements performed on bovine blood are reported, thus demonstrating the applicability of the proposed measurement method.


2010 - Contactless Two-Axis Inclination Measurement System Using Planar Flux-Gate Sensor [Articolo su rivista]
Rovati, Luigi; Cattini, Stefano
abstract

A tilt-sensitive measuring system exploiting a low-cost planar printed-circuit-board (PCB) flux-gate sensor is described. We propose a system topology that exploits two magnets and a flux-gate sensor to realize a two-axis tilt-sensitive measuring system. The sensing configuration has been investigated using electromagnetic modeling software first. Then, the prototype characterization has shown system sensitivity up to 4 V/° and integral nonlinearity (INL) down to 1%. Mainly limited by the mechanical implementation, the obtained system dynamic range is about ±3°.


2010 - Fast optical changes recorded in primary visual cortex during visual stimulation [Poster]
Malagoli, Andrea; Fonda, Sergio; Rovati, Luigi
abstract

Near infrared spectroscopy (NIRS) is now an established non-invasively clinical technique to detect changes in blood flow [1][2]. In recent studies, NIRS, is instead used to detect neuronal activities, consistent with evoked potentials, arising from changes in light scattering and diffusion related either to membrane potential variations and cell swelling [3]. These optical response, called fast NIRS, occurs with a latency time of an order of milliseconds after stimulus presentation. After the first studies performed with a continuous light system [4], we tested the ability to detect an optical response due to visual stimulation with a frequency modulated light source.


2010 - Image processing algorithms for ocular fundus reflectometry [Relazione in Atti di Convegno]
Nithiyanantham, Palanisamy; Ilaria, Bruschi; Matteo, Bonaiuti; Rovati, Luigi; Charles E., Riva
abstract

Ocular fundus reflectometry is a technique aimed at the in-vivo measurement of the reflectance of the tissues of the ocular fundus. Studies have demonstrated a correlation between optical and physiological properties of such tissues in humans and the existence of a control mechanism, called neuro-vascular coupling (NC), which adjusts local blood perfusion to support vision-induced neural activity. We developed an instrument for functional imaging of the neural tissues of the ocular fundus based on reflectance measurements to study the NC. The images acquired with the instrument needed processing to work out reflectance time-courses. The algorithm exploited previously requires long computational time, provides poor discrimination of objects and need manual intervention. We have developed a fully automatic algorithm based on differential multiscale framework for the processing of the images of the ocular fundus with reduced computational time. This algorithm is reasonably efficient to determine relative translational displacement (translation and rotation) between the images and also to remove the geometric distortion. Simulation results performed on the fundus images show that differential multiscale framework based image registration reduces computational times up-to one fourth of the time required by the general purpose algorithm, and provides better alignment precision.


2010 - Low-Cost Optical Flowmeter With Analog Front-End Electronics for Blood Extracorporeal Circulators [Articolo su rivista]
M., Norgia; A., Pesatori; Rovati, Luigi
abstract

The design and realization of a new low-cost instrument for real-time measurement of blood flow particularly developed for extracorporeal blood circulator systems are presented. A self-mixing interferometric technique combined with a dedicated analog signal processing system was adopted to perform an accurate flow measurement. The developed system exhibits an accuracy lower than 3%. The cost of the entire measuring system has been estimated to be about 50 euros.


2010 - Micro-power photovoltaic harvester based on a frequency-to-voltage MPPT tracker [Articolo su rivista]
Chini, Alessandro; Rovati, Luigi
abstract

A micro-power circuit for photovoltaic energy harvesting applications is presented. The system can work in different lighting power ranging from a few tens of microwatts to milliwatts maintaining tracking of the maximum output power operational conditions of the photovoltaic cells. The energy harvesting efficiency ranges from 30 to 70%.


2010 - Optical flowmeter sensor for blood circulators [Relazione in Atti di Convegno]
Michele, Norgia; Alessandro, Pesatori; Rovati, Luigi
abstract

This work describes the design and realization of a new low-cost instrument for real time measurement of blood flow, especially developed for dialysis machine monitoring. The instrument is realized by means of a self-mixing interferometer and a dedicated data elaboration system.


2010 - Self-mixing laser Doppler: a model for extracorporeal blood flow measurement [Relazione in Atti di Convegno]
M., Norgia; A., Pesatori; Rovati, Luigi
abstract

A theory is developed to study the spectral characteristics of the signal acquired from self-mixing laser Doppler of extracorporeal blood flow. Doppler shifts is generated by erythrocyte cells interacting with the illumination photons. The resulting signal is mixed in the laser cavity to generate the sensor output. In order to predict analytically the spectrum of the Doppler signal, is assumed:week optical feedback, single scattering event and a Gaussian illumination beam. Predictions are verified by measurements on blood in extracorporeal circulation system.


2009 - Alpha-particle detection based on the BJT detector and simple, IC-based readout electronics [Articolo su rivista]
Rovati, Luigi; S., Bettarini; Bonaiuti, Matteo; L., Bosisio; G. F., Dalla Betta; V., Tyzhnevyi; Verzellesi, Giovanni; N., Zorzi
abstract

In this paper we propose a portable instrument for alpha-particle detection based on apreviously-developed BJT detector and a simple, IC-based readout electronics. Experimental testsof the BJT detector and readout electronics are reported. Numerical simulations are adopted topredict the performance enhancement achievable with optimized BJT detectors.


2009 - Analysis of the effects of flicker on the blood-flow variation in the human eye [Articolo su rivista]
Rovati, Luigi; G., Salvatori; R., Tinarelli; L., Peretto
abstract

Flicker annoyance measurement, regardless if it isperformed by processing the supplying voltage or by evaluatingthe light emitted by the lamp, relies on the assumption of a propermodel of the behavior of the complex eye–brain system in thepresence of fluctuating light. The only experimental data availableare the ones obtained, for a certain incandescent lamp, by askingseveral people to report their perception about the flicker to whichthey were subjected. In this paper, the possibility of achieving an“objective” evaluation of the flicker effects on a human subjectis investigated. In particular, the increment of the blood flow in avessel at the optic nerve is considered and taken as a possible indexof annoyance due to flicker.


2009 - Development of a low-cost pH sensor based on plastic optical fibers [Relazione in Atti di Convegno]
Rovati, Luigi; Fabbri, Paola; F., Pilati
abstract

The goal of this study is to develop the technology to achieve pH sensing using low-cost polymeric optical fibers. The tip of a low-cost plastic optical fiber is covered by a sensitive dye entrapped in an organic-inorganic hybrid matrix obtained by solgel process. The behaviors of this sensing arrangement have been investigated for a specific dye, namely Phenol Red.


2009 - Measurement of the pupil diameter under different light stimula [Relazione in Atti di Convegno]
R., Tinarelli; Rovati, Luigi; M. G., Masi; L., Peretto
abstract

The subjectivity and the limitation of the standardmethod for the flicker evaluation have suggested the research ofdifferent approaches. The intent is to achieve objectiveinformation on the state of annoyance of a human being subjectedto light flicker. Recently, a technique based on the analysis of thepupil size variation has been proposed. This paper studies theeffects of different light stimula on pupil diameter and highlightsome interesting results.


2009 - Optical flowmeter for blood extracorporeal circulators [Relazione in Atti di Convegno]
A., Pesatori; M., Norgia; Rovati, Luigi
abstract

This work describes the design and realization of a new low-cost instrument for real time measurement of blood flow, especially developed for dialysis machine monitoring. The instrument is realized by means of a self-mixing interferometer and a dedicated data elaboration system.


2009 - Two-axis inclination measurement system based on a planar flux-gate sensor [Relazione in Atti di Convegno]
Cattini, Stefano; Rovati, Luigi
abstract

tilt-sensitive measuring system exploiting a low-cost planar printed-circuit-board (PCB) flux-gate sensor is described. We propose a system topology that exploits two magnets and a flux-gate sensor to realize a two-axis tilt-sensitive measuring system. The sensing configuration has been investigated using electromagnetic modeling software first. Then, the prototype characterization has shown system sensitivity up to 4 V/ð and integral nonlinearity (INL) down to 1%. Mainly limited by the mechanical implementation, the obtained system dynamic range is about ñ3ð.


2009 - UV-LEDs for monitoring dialysis adequacy [Articolo su rivista]
Rovati, Luigi; Cattini, Stefano
abstract

Abstract—New Ultraviolet (C band: 280 nm − 100 nm) lightemitting diodes (UV-C LEDs) have been characterized to evaluatetheir potential applicability in the development of a simple low–cost optical adequacy sensor for continuous online measurementson spent dialysate. This approach would allow us to avoid theuse of bulky and expensive spectrometers in the monitor systems.The reported results could be useful for the system developmenteven if different critical aspects such as LED reliability, meanlifetime, and emitted and transmitted power monitoring should betaken into consideration. Nevertheless, the experimental activityhas shown that the system can be implemented with few opticalcomponents and that the assembly can be made simple.


2008 - A pupil size measurement system for the analysis of the impact of flicker on human being [Relazione in Atti di Convegno]
M. G., Masi; L., Peretto; R., Tinarelli; Rovati, Luigi
abstract

A pupil size measurement system for the analysis of the impact of flicker on human being


2008 - A simple readout electronics for automatic power controlled self-mixing laser diode systems [Articolo su rivista]
CATTINI, Stefano; ROVATI, Luigi
abstract

he paper describes a simple electronic circuit to drive a laser diode for self-mixing interferometry. The network integrates a stable commercial automatic power controller and a current mirror based readout of the interferometric signal. The first prototype version of the circuit has been realized and characterized. The system allows easily performing precise interferometric measurements with no thermostatic circuitry to stabilize the laser diode temperature and an automatic control gain network to compensate emitted optical power fluctuations. To achieve this result, in the paper a specific calibration procedure to be performed is described.


2008 - Measuring Dynamics of Scattering Centers in the Ocular Fundus [Articolo su rivista]
Rovati, Luigi; Cattini, Stefano; F., Viola; G., Staurenghi
abstract

The study is focused on the analysis of the diffusing-wave-spectroscopy signalrecorded invivo on the ocular fundus of a rabbit eye. The motion of the scattered sites wasmeasured as a function of the pressure exerted by a Goldmann contact lens and during themoderate temperature increase induced by a therapeutic laser diode. Temporal fluctuations ofthe signal revel motion of molecules and thus changes in tissues temperature andchorioretinal blood velocity. Experimental results show the ability of the system to detectmotion of the scattering sites in the ocular fundus layers during variations of the ocularpressure and laser heating.


2008 - Modeling of the physiological behavior of human vision system under flicker condition [Relazione in Atti di Convegno]
M. G., Masi; L., Peretto; R., Tinarelli; Rovati, Luigi
abstract

The impression of visual unsteadiness caused by the fluctuation of the voltage supplying a lamp (flicker) is a power quality phenomena evaluated according to standards endorsed by both the IEC and IEEE. However, it is widely recognized that flicker measurements provide a correct estimation of the relevant human being annoyance only if a certain light source is considered (60 W, 120 V incandescent filament-lamp). In recent years, approaches based on the analysis of the light have been proposed. Nevertheless, all these lack of any kind of robust validation. In this respect, this paper presents the results of a study aimed at investigating on the performance of different methods for correlating the annoyance due to flicker with the behavior of some human physiological aspects.


2008 - Noninvasive Measurements of Glucose in the Human Body Using Polarimetry and Brewster Reflection off of the Eye Lens [Capitolo/Saggio]
Rovati, Luigi; R., Ansari
abstract

Noninvasive Measurements of Glucose in the Human Body Using Polarimetry and Brewster Reflection off of the Eye Lens


2008 - On the use of deep UV-LEDs for monitoring dialysis [Relazione in Atti di Convegno]
Rovati, Luigi; Cattini, Stefano
abstract

The new UV-C LEDs have been characterized to evaluate their potential applicability in the development of a simple, low-cost optical adequacy sensor for continuous, on-line measurements on spent dialysate. This approach would allow us to avoid the use of bulky and expensive spectrometers in the monitor systems. The reported results could be useful for the system development; nevertheless, different critical aspects such as LEDs reliability, mean life time and emitted and transmitted power-monitoring should be taken in consideration.


2008 - Optic Nerve Reflectance Variations During Neural Activity [Abstract in Rivista]
M., Bonaiuti; ROVATI, Luigi; C. E., Riva
abstract

PurposeChanges in optic nerve reflectance in response to visual stimulation have been demonstrated in the visible wavelengths (Crittin and Riva, 2004) and in presence of flash stimulation in monkeys (Hanazono et al., IOVS 2007). The purpose of the study was to determine whether diffuse flicker-induced reflectance changes in the human optic nerve could be detected using near-infrared light. MethodsSix 770-nm reflectance measurements were carried out on a healthy, informed and consenting volunteer, by means of a PC-controlled ocular fundus reflectometer based on a commercial fundus camera and modified for the purpose of the study. Neural activity was evoked by 535-nm diffuse square wave flicker stimulation at 12Hz. The measurement protocol consisted of 6 successive reflectance registrations at 770nm, each consisting of a 20s baseline followed by 60s flicker. We investigated two different measuring sites in the optic nerve papilla deprived of visible vessels, near the temporal rim. The reflectance changes measured in a control region outside the optic nerve were subtracted from the reflectance variations obtained from the two investigation sites, to cancel out the effects of involuntary eye and head movements. ResultsFlicker induced a significant decrease in near-infrared reflectance, which reached a maximum value at approximately 60s of stimulation. The decrease with respect to control amounted to -2.6% {+/-} 1.4% (mean {+/-} 1 standard error) for measuring site 1 and -2.4% {+/-} 1.4% for measuring site 2. ConclusionsFlicker stimulation induces a significant decrease in near-infrared reflectance in the temporal region of the human optic nerve papilla, confirming previous near-infrared reflectance findings in monkeys. This decrease is most probably due to changes in blood volume during neural activity.


2008 - Radon alpha-ray detector based on a high-resistivity-silicon BJT and a low-cost readout electronics [Relazione in Atti di Convegno]
Rovati, Luigi; Verzellesi, Giovanni; Bonaiuti, Matteo; G., Batignani; L., Bosisio; G. F., Dalla Betta; G., Giacomini; C., Piemonte; N., Zorzi
abstract

Radon dosimetry yields valuable information about radioactive health risks in closed environments. Indeed, World Health Organization (WHO) and the International Agency for Research on Cancer (IARC) have recently classified radon as a human carcinogen and have demonstrated a correlation between environmental radon concentration and lung cancer risk. Dose measurements are traditionally based on laboratory analysis of alpha-ray traces in ionization chambers exposed to environmental air. In this paper we propose a portable instrument for real-time radon alpha-ray detection based on a previously-developed high-resistivity-silicon BJT sensor and a low-cost, IC-based readout electronics.


2008 - SENSORI DI pH IBRIDI ORGANICI-INORGANICI APPLICABILI A FIBRE OTTICHE [Relazione in Atti di Convegno]
Fabbri, Paola; Messori, Massimo; Pilati, Francesco; Rovati, Luigi
abstract

In questo lavoro è stata studiata la possibilità di preparare mediante tecnica sol-gel un sensore per misure di pH applicabile in punta di fibra ottica, che abbia come eventuali applicazioni l’utilizzo in pH-metria esofagea per monitorare i livelli di pH nell’esofago in pazienti affetti da reflusso gatroesofageo, il monitoraggio dei livelli di acidità o di basicità dei vapori industriali, di acque reflue, ecc. Si tratta di un sensore micro-invasivo che, grazie alla miniaturizzazione offerta dalla fibra ottica, consente di effettuare un monitoraggio continuativo del pH anche in situazioni complesse come la misura clinica a livello esofageo.


2007 - A Measurement System for the Analysis of the Response of the Human Eye to the Light Flicker [Articolo su rivista]
Peretto, L; Rovati, Luigi; Salvatori, G; Tinarelli, R; Emanuel, A. E.
abstract

The response of the human eye to flicker depends on the type of lamp used. Standard flickermeters measure the voltage across the lamp and assumes a 60-W incandescent lamp as a light source. When a different lamp is the light flicker source, standard flickermeters give erroneous results. This paper presents a dynamic model of the eye-brain response to flicker. The model is based on the analysis of the light emitted by the lamp. A suitable measurement system has been developed, and three different kinds of lamps have been considered. Experimental results show how the emitted light spectra and the human eye response to different colors combined to determine the level of annoyance. The uncertainty affecting such results, which arises from the hardware of the developed system, has been also estimated.


2007 - A system for functional imaging of the ocular fundus [Relazione in Atti di Convegno]
Matteo, Bonaiuti; Rovati, Luigi; Charles E., Riva
abstract

Neurovascular coupling in the optic nerve is the physiological mechanism that adjusts the blood perfusion in the microcirculation of the optic nerve to support the neural activity induced by vision. The resulting variations in blood flow and thus in neural tissue oxygenation induce changes in the optical properties of the tissues. These variations can be detected optically as reflectivity changes in the neural tissues, i.e. the retina and optic nerve disk. To achieve a better understanding of the mechanisms underlying the neurovascular coupling, our study is aimed at the evaluation of reflectance changes of the optic nerve induced by visual stimulation. For this purpose, an ocular fundus reflectometer has been developed.


2007 - Application of the BJT Detector for Simple, Low-Cost, and Low-Power Alpha-Particle Detection Systems [Relazione in Atti di Convegno]
Verzellesi, Giovanni; G., Batignani; Bonaiuti, Matteo; L., Bosisio; G. F., DALLA BETTA; G., Giacomini; C., Piemonte; Rovati, Luigi; N., Zorzi
abstract

We present a simple, low-cost, and low-power alpha-particle detection system for environmental radioactivity monitoring. The system exploits a previuosly-developed high- resistivity-silicon detector with internal amplification capability based on the bipolar-transistor (BJT) effect and readout electronics based on commercial IC's. Two-dimensional numerical device simulations are adopted to assess the feasibility of the BJT detector as an alpha-particle detector that can be operated, without losing its internal signal amplification capability, with floating base and low collector voltages, so that device technology can be kept simple, very small DC power consumption can be achieved, and a single 5-V power-supply voltage can be used for readout electronics and detector biasing. The charge amplification accomplished by the BJT detector allows a single, commercial chip to be adopted, to perform charge preamplification and 20-bit A/D conversion. The digital output is sent to a low-cost microcontroller that can be periodically interrogated through the IR port. The cost of the readout electronics is in the order of 60$ and it can operate with standard Li-ion battery for about 60 hours.


2007 - Closed loop PCB Fluxgate without compensation coil [Relazione in Atti di Convegno]
Rovati, Luigi; Cattini, Stefano; Marchesi, M; Dallago, E.
abstract

We propose a circuit arrangement that exploits the sense coil of a planar PCB fluxgate to generate the compensation static field in the closed loop configuration. This approach allows to overcome the difficulties related to the optimization of the coupling efficiency between compensation and sense coil. Experimental results are presented to demonstrate the feasibility of the proposed approach.


2007 - Experimental Evaluation of Flicker Effects on Human Subjects [Relazione in Atti di Convegno]
L., Peretto; C. E., Riva; Rovati, Luigi; G., Salvatori; R., Tinarelli
abstract

Flicker annoyance measurement, no matter if it is performed by processing the supplying voltage or by evaluating the light emitted by the lamp, relies on the assumption of a proper model of the behavior of the complex eye-brain system in presence of fluctuating light. The only experimental data available are the ones obtained, for a certain incandescent lamp, by asking several people to report their perception about flicker they were subjected to. In this paper, the possibility of achieving an "objective" evaluation of the flicker effects on human subject is investigated. In particular, the increment of the blood flow in a vessel at the optic nerve papilla is considered and taken as possible index of the annoyance due to flicker.


2007 - In-vivo diffusing-wave-spectroscopy measurements of the ocular fundus [Articolo su rivista]
Rovati, Luigi; Cattini, Stefano; N., Zambelli; F., Viola; G., Staurenghi
abstract

We present what is to our knowledge the first observation of a diffusing-wave-spectroscopy signal recorded in-vivo on the ocular fundus. A modified ophthalmic microscope was developed which can acquire diffusing-wave-spectroscopy signal from the eye fundus. The diffusing-wave-spectroscopy signal was recorded in-vivo on a rabbit eye during transpupillary thermotherapy. Experimental results show the ability of the system to detect motion of the scattering sites in the ocular fundus layers during laser thermal heating. (c) 2007 Optical Society of America.


2007 - LEGISLATIVE, TECHNOLOGICAL, ADMINISTRATIVE, ECONOMICAL AND ORGANIZATIONAL ASPECTS OF THE EXECUTIVE RAEE AND ROHS [Relazione in Atti di Convegno]
Barbieri, Luisa; Cannio, Maria; Cassanelli, Giulia; Colombo, Paolo; Pozzi, Paolo; Rabitti, Daniela; Rimini, Bianca; Rovati, Luigi
abstract

-The Italian Decree D. Lgs. n. 151/2005 and subsequent changes and supplements in agreement with Directives WEEE 2002/96/CE and 2003/108/CE “for the recovery and recycling of waste from electric and electronic equipments” and Directive RoHS 2002/95/CE “on the restriction of the use of certain hazardous substances in electrical and electronic equipment” has been analysed here. In particular, the aim of this work is to introduce legal, technological, administrative outcomes about interpretation and application of the D. Lgs. 151/2005. The main legislative novelty is represented by the Extended Producer Responsibility (EPR) that it is transferred in the burden of producers and distributors which have to support economically national systems for the WEEE recovery and treatment at the end of life. The correct management of the WEEE nevertheless, parallel of new requirements, offers to the producers stimulating opportunity both in the field of Integrated Product Policy and in the optimization of the distribution/collection nets.


2007 - Measurement of the Retina and Choroid Diffusion Coefficients During TTT [Abstract in Rivista]
F., Viola; N., Zambelli; CATTINI, Stefano; D., Galimberti; R., Ratiglia; G., Staurenghi; ROVATI, Luigi
abstract

PurposeDiffusing-wave-spectroscopy (DWS) is a technique able to monitor microscopic movements in turbid media. In this study, we report the first observation of a DWS signal recorded in-vivo on the ocular fundus of a rabbit eye during a laser thermal treatment. MethodsA modified slit-lamp with a 30/70 beam splitter and a custom made fibers adapters including the collimation lenses, equipped with a standard therapy laser diode, was used. The motion of the scattered sites in the fundus was varied using transpupillary thermotherapy (TTT) for 60 seconds with a power settings of 200 mW. The scattered light was then guided by the single mode fiber to a single photon counting module (SPCM-AQR-14-FC, Perkin Elmer). The electrical signal from the SPCM was processed by a digital correlator (FLEX99S160B, Correlator.com) to acquire the normalized intensity autocorrelation function. Thus the APD photodiode was substituted by a HeNe laser in order to define the collection area. The distance between illumination and collection spots was estimated to be about 2 mm. Immediately before TTT, the APD photodiode was reconnected to the receiving fiber and three autocorrelation functions were acquired each 5 seconds. Next, we started the laser thermal treatment. During the 60-second NIR laser exposure, an autocorrelation functions was acquired each 5 seconds for a total of 12 readings. After the TTT three autocorrelation functions were acquired each 5 seconds. ResultsAutocorrelation functions exhibit a similar trend and a common plateau in the delay time range (200ms, 1000ms). The mean-squared displacements of the scattering sites in the short and long delay range were calculated for all the acquired autocorrelation functions. We fit a linear function to in the long delay range and a quadratic function in the short delay range, then we evaluated the diffusion coefficient of the scatterers in the retina and choroid layer. The values estimated at the different stages of the experiment show as in the retina the temperature induced a motion of the scatterers that increases monotonically during the treatment. The choroidal diffusion coefficient induced by the temperature elevation shows a very well defined sharp step-down. ConclusionsA correlation was found between DWS signal and motion of the scatterers on the ocular fundus, therefore this technique may be used to evaluate useful parameters during laser treatments.


2007 - Optical and electrical recording of neural activity evoked by graded contrast visual stimulus [Articolo su rivista]
Rovati, Luigi; Salvatori, G; Bulf, Luca; Fonda, Sergio
abstract

BackgroundBrain activity has been investigated by several methods with different principles, notably optical ones. Each method may offer information on distinct physiological or pathological aspects of brain function. The ideal instrument to measure brain activity should include complementary techniques and integrate the resultant information. As a "low cost" approach towards this objective, we combined the well-grounded electroencephalography technique with the newer near infrared spectroscopy methods to investigate human visual function.MethodsThe article describes an embedded instrumentation combining a continuous-wave near-infrared spectroscopy system and an electroencephalography system to simultaneously monitor functional hemodynamics and electrical activity. Near infrared spectroscopy (NIRS) signal depends on the light absorption spectra of haemoglobin and measures the blood volume and blood oxygenation regulation supporting the neural activity. The NIRS and visual evoked potential (VEP) are concurrently acquired during steady state visual stimulation, at 8 Hz, with a b/w "windmill" pattern, in nine human subjects. The pattern contrast is varied (1%, 10%, 100%) according to a stimulation protocol.ResultsIn this study, we present the measuring system; the results consist in concurrent recordings of hemodynamic changes and evoked potential responses emerging from different contrast levels of a patterned stimulus.The concentration of [HbO2] increases and [HHb] decreases after the onset of the stimulus. Their variation shows a clear relationship with the contrast value: large contrast produce huge difference in concentration, while low contrast provokes small concentration difference. This behaviour is similar to the already known relationship between VEP response amplitude and contrast.ConclusionThe simultaneous recording and analysis of NIRS and VEP signals in humans during visual stimulation with a b/w pattern at variable contrast, demonstrates a strong linear correlation between hemodynamic changes and evoked potential amplitude. Furthermore both responses present a logarithmic profile with stimulus contrast.


2007 - Optical monitoring of the chorioretinal status during retinal laser thermotherapy [Relazione in Atti di Convegno]
Rovati, Luigi; Nicola, Zambelli; Cattini, Stefano; Francesco, Viola; Giovanni, Staurenghi
abstract

As a consequence of pigmentation inhomogeneities and/or different vascularizations of the retinal tissue, retinal laser thermo-treatments are often over- or underexposed. Our study is focused on the determination of suitable parameters to identify a convenient end-point of the laser treatment. The proposed method is based on the analysis of the temporal fluctuations of the scattered light intensity from the spot area. Motion of molecules and thus frequency of the scattered light fluctuations changes during the laser exposure due to variations of temperature, blood flow and optical parameters, i.e. absorption and scattering coefficient.


2007 - Self-mixing laser velocimeter for retinal blood flow measurements [Relazione in Atti di Convegno]
Cattini, Stefano; Giorgia, Salvatori; Rovati, Luigi
abstract

A Doppler velocimeter exploiting a self-mixing laser diode is proposed. The system has been design to evaluate the retinal blood flow velocity. The central frequency of the Doppler band obtained from the self-mixing laser diode measurement is related to the blood flow velocity in the vessel under test. The measurement can be done under the light-intensity feedback ratio below -100 dB without using highly sensitive electronics since the laser acts as a high-efficiency mixer oscillator and a shot-noise-limited quantum detector. The advantages in adopting such technique consist in its low cost, easiness of implementation and small size. Moreover, the self-mixing laser diode method offers the advantage to have the excitation and measurement beams spatially overlapped overcoming the alignment difficulty due to limited optical accessibility imposed by the finite aperture of the pupil.


2006 - A PC-CONTROLLED REFLECTOMETER FOR FUNCTIONAL IMAGING OF OCULAR FUNDUS [Relazione in Atti di Convegno]
M., Bonaiuti; Rovati, Luigi; C., Riva
abstract

The paper presents an imaging reflectometerdesigned to detect flicker-induced reflectance changes of theocular fundus. The system is based on a modified funduscamera completely controlled by a personal computer viaUSB interface.The system allows in-vivo functional imaging of the ocularfundus in the near-infrared region with flicker light stimulusin the visible spectrum.


2006 - Combined bio-engineering and neurophysiological in vivo technologies allow studying rat brain metabolism and neuronal activities in vivo in real time [Relazione in Atti di Convegno]
F., Crespi; M., Donini; A., Bandera; F., Congestri; C., Heidbreder; Rovati, Luigi
abstract

Franz Jöbsis first used near infrared spectroscopy (NIRS) as a tool for the in vivo monitoring of tissue oxygenation [1]. Today, NIRS instruments are more and more used in clinical environments since these systems are now easy to use, sensitive, robust, give rapid analysis and have multiple measuring points [2-3]. In the present work, optic fibre probes were used as optical head of a CW-NIR instrument adapted for in vivo NIRS measurements in the brain of rodents. This prototype was designed for non-invasive analysis of the two main forms of haemoglobin: oxy-haemoglobin (HbΟ2) and deoxy-haemoglobin (Hb), chromophores present in biological tissues. In the present experiments it was applied to measure non- invasively HbO2 and Hb levels in the rat brain; that are markers of the degree of tissue oxygenation, thus providing an index of blood levels and therefore of brain metabolism. In addition, the same animals set for central NIRS studies, were also surgically prepared for electrophysiological monitoring of cell firing in discrete brain areas. These are raphe dorsalis nucleus, locus coeruleus, ventral tegmental area that are defined as main serotoninergic, noradrenergic and dopaminergic cell containing regions of the CNS and therefore involved in the major cerebral syndromes. Then, following a control recording period, exogenous oxygen (02, 0.1bar, 2min) or carbon dioxide (C02 0.1bar, 20min) was inflated orally. The data gathered indicate an original relationship between NIRS analysis of brain metabolism and electrical changes in three major nuclei of CNS involved in neurophysiologic and pathologic activities.


2006 - Combining Near-Infrared Spectroscopy and Electroencephalography to Monitor Brain Function [Relazione in Atti di Convegno]
Salvatori, Giorgia; Bulf, Luca; Fonda, Sergio; Rovati, Luigi
abstract

We propose to embed a continuous-wave near-infrared spectroscopy system within an electroencephalography system to perform functional hemodynamic and neural response simultaneously. In this study, we present the measuring system and the results consisting in changes of oxyhemoglobin and deoxyhemoglobin derived from continuous-wave near-infrared spectroscopy data and the evoked potential responses derived from the electroencephalography recordings. A checkerboard stimulus was adopted to elicit a response signal from the visual cortex. The results collected demonstrate that near infrared spectroscopy can detect task-induced changes in hemodynamics.


2006 - HOLLOW BEAM GEOMETRY FOR DIFFUSING TEMPORAL LIGHT CORRELATION [Relazione in Atti di Convegno]
Rovati, Luigi; N., Zambelli; Cattini, Stefano; G., Salvatori
abstract

The paper presents an optical setup for diffusingtemporal light spectroscopy of living tissues. The systemallows to study the dynamical properties of living tissuesmolecules. The proposed approach exploits the hollow beamgeometry in conjunction to mode-selective detection. Firstexperiments, aimed to demonstrate the functionality of themeasuring system, have been performed.


2006 - Instrumentation and calibration protocol for a continuous wave near infrared hemoximeter [Articolo su rivista]
G., Salvatori; K. I., Suh; R. R., Ansari; Rovati, Luigi
abstract

Quantification of hemoglobin content in vivo using continuous wave (CW) near infrared spectroscopy requires an accurate calibration of the measuring system. The authors introduce a recently developed instrument and focus their attention on the calibration issue, proposing a calibration procedure specifically designed for their system, but which can be easily generalized for other CW near-infrared systems. In the paper, the most important calibration procedures and the results obtained are discussed in detail.


2006 - Investigation on the Response of the Human Eye to the Light Flicker Produced by Different Lamps [Relazione in Atti di Convegno]
Peretto, L; Rovati, Luigi; Salvatori, G; Tinarelli, R; Emanuel, A. E.
abstract

The response of the human eye to flicker depends on the type of lamp used. The standard flickermeter is based on the measurement of voltage and assumes the light source to be a 60 W incandescent lamp. When a different lamp is the source of light flicker, the standard flickermeter gives erroneous results. This paper presents a dynamic model of the eye-brain response to flicker. The model is based on the analysis of the light emitted by the lamp. A suitable measurement system has been developed and three different kinds of lamps have been considered. Experimental results show how the emitted light spectra and the human eye response to different colors determine the level of annoyance


2006 - Near-infrared oxymeter biosensor prototype for non-invasive in vivo analysis of rat brain oxygenation: effects of drugs of abuse [Articolo su rivista]
Crespi, F; Donini, M; Bandera, A; Congestri, F; Formenti, F; Sonntag, V; Heidbreder, C; Rovati, Luigi
abstract

The feasibility of non-invasive analysis of brain activities was studied in the attempt to overcome the major limitation of actual in vivo methodologies, i.e. invasiveness. Optic fibre probes were used as the optical head of a novel, highly sensitive near-infrared continuous wave spectroscopy (CW-NIR) instrument. This prototype was designed for non-invasive analysis of the two main forms of haemoglobin: oxy-haemoglobin (HbO2) and deoxy-haemoglobin (Hb), chromophores present in biological tissues. It was tested in peripheral tissue (human gastrocnemius muscle) and then reset to perform the measurement on rat brain. In animal studies, the optical head was firmly placed using stereotaxic apparatus upon the sagittal line of the head of anaesthetized adult rats, without any surgery. Then pharmacological treatments with saline (300 µl s.c.) amphetamine (2 mg kg−1) or nicotine (0.4 mg kg−1) were performed. Within 10–20 min amphetamine substantially increased HbO2 and reduced Hb control levels. Nicotine produced a rapid initial increase followed by a decrease in HbO2. In contrast to amphetamine, nicotine treatment also reduced Hb and blood volume. These results support the capacity of our CW-NIR prototype to measure non-invasively HbO2 and Hb levels in the rat brain, that are markers of the degree of tissue oxygenation, thus providing an index of blood levels and therefore of brain metabolism.


2006 - Optic Nerve Blood Flow Response to Flicker Can Be Described by a Second Order Linear System Model [Abstract in Rivista]
M., Bonaiuti; C. E., Riva; ROVATI, Luigi
abstract

Purpose: Neurovascular coupling (NC) in the retinal tissue is the mechanism that controls the blood flow to support neural activity associated with the process of vision. Diffuse luminance flicker increases retinal and optic nerve blood flow in humans, indicating the ability of the retina to adapt to different metabolic demands. The control system analysis allows the description of the main dynamic features of this regulation system. Methods: Six healthy adult volunteers aged 25-62 years were included in the study. Informed consent was obtained from the subjects. Blood flow was measured from the optic nerve temporal rim by means of laser Doppler flowmetry. During these measurements a 15Hz square wave diffuse flicker stimulation was applied during 1 to 8 minutes through the illumination pathway of the laser Doppler fundus camera. The time-course of the flow underwent a 10-point lagging running-averaging process and then was fitted with the equation of a modified second-order control system G(s) consisting of the cascade of a Proportional-Derivative (PD) term, a second-order Filter (F2) and an Integrator term (INT). The characteristic parameters of G(s) to be determined were: the undamped natural frequency ({omega}) of F2, the damping factor ({xi}) of F2, the gain (K) of PD, the rate time (Tv) of PD and the integrator time constant ({tau}) of INT. The values for the parameters of G(s) related to the input flow time-courses were thus obtained. Results: Flicker-induced optic nerve blood flow changes could be well fitted by the response of G(s) to the Heaviside step function (correlation R2&gt;0.66). Characteristic parameters of G(s) were calculated as mean values {+/-} standard errors and the following results were obtained:{omega} = 2.31{+/-}1.57 rad/sec,{xi} = 0.28{+/-}0.1, K = 180.75{+/-}11.76, Tv = 2.67{+/-}1.62 sec,{tau} = 5.95{+/-}1.93 sec. Conclusions: The response of optic nerve blood flow to diffuse luminance flicker can be described by a second order linear system. Further studies are needed to establish the physiological basis of the various terms of the control cascade.


2005 - A PC-controlled nonincremental distance meter based on a comb-spectrum combined with a frequency-modulated continuous wave interferometer [Articolo su rivista]
Rovati, Luigi; Salvatori, G; Bonaiuti, M.
abstract

In this paper, a PC-controlled nonincremental interferometer that integrates frequency-modulated continuous wave (FMCW) and dispersive comb spectrum (DCS) techniques is presented. This system takes advantage of the wide measuring range of the FMCW technique and of the high resolution of the DCS technique. The system prototype presented in this paper performs measurements over a range of 30 mm with an accuracy of about 600 nm. The proposed combined interferometer is expected to also have applications in biomedical frameworks.


2005 - A true-phase polarimetric system to study bi-anisotropic media [Relazione in Atti di Convegno]
Rovati, Luigi; Ruggeri, M; Salvatori, G.
abstract

The article describes a true-phase polarimeter designed to study bi-anisotropic media. Exploiting a simple optical setup based on two He-Ne lasers and a precise analogue phase-to-voltage converter, the measuring system exhibits high sensitivity and excellent rejection ambient light


2005 - An optical technique for monitoring chorioretinal temperature during transpupillary thermotherapy [Relazione in Atti di Convegno]
Rovati, Luigi; Nicola, Zambelli; Giovanni, Staurenghi
abstract

The aim of this study is to explore the possibility of correlating the temporal fluctuations of scattered light intensity from the chorioretinal tissue during Transpupillary Thermotherapy and the temperature of the irradiated tissue. The chorioretinal tissue is a mixture of macromolecules that either are rigidly fixed into a structural matrix or can move. The possible motions are induced by the blood flow and by the temperature. Therefore, by analyzing the scattered intensity fluctuations induced by the molecules motion, the retinal tissue temperature can be recovered. In this paper, we present the theory supporting this idea and the results of a preliminary experimental activity performed on enucleated bovine eyes.


2005 - Analysis of the Temporal Fluctuations of the Laser Light Intensity Diffused by the Chorioretinal Tissue During Transpupillary Thermotherapy (TTT) [Abstract in Rivista]
G., Staurenghi; Rovati, Luigi
abstract

Purpose: Chorioretinal tissue is a mixture of macromolecules that either are rigidly fixed into a structural matrix or can move. Fluctuation of the scattered light is related not only to possible molecules motions induced by the blood flow and by the temperature but also to the absorption and scattering coefficients which are temperature depended. Analyzing the light scattering fluctuations the retinal tissue temperature can be recovered. Methods: We conducted two experiments using fresh enucleated bovine eyes. The first experiment was performed on an eye cut at the equator to include retinal tissue and placed into a semispherical holder designed to heat the tissue at a known temperature by using a Peltier cell. A focused Helium-Neon laser was used to illuminate the central retina close to the fovea. The collection of the diffused radiation was performed by a single-mode fiber connected to a single photon counting (SPCM). The electrical signal from the SPCM was processed by a digital correlator to acquire the intensity autocorrelation function (ACF) at different retina temperatures. The second experiment was performed using an intact eye and the excitation laser was a standard therapy laser diode. The laser settings were: power=500mW, diameter spot=1mm, duration=60sec. The collection of the diffused radiation was performed exploiting the same setup used in the first experiment; the intensity ACF was acquired each 10 seconds. Results: The average decay time of the autocorrelation functions acquired during the first experiment exhibited a linear trend as a function of the temperature in the range 20-50 {degrees}C. The Pearson's correlation coefficient of the linear fit was R=0.99. During 500mW laser irradiation the average decay time of the ACF increased for the first 50 minutes then the last acquisition showed a decreased value. The trend of the average decay time of the ACF during irradiation showed a fast increasing of the temperature in the first 10 seconds of irradiation, then we observed a linear slow increasing of the temperature in the time interval (10min,50min). The fall of the average decay time in the last 10 seconds could be due to a deterioration of tissue (whitening). Conclusions: Analysis of the temporal fluctuations of the scattered laser light intensity could be used to determine in-vivo the chorioretinal temperature during TTT. The preliminary data presented shows an excellent correlation between the retinal temperature and the average decay time of the intensity ACF.


2005 - Design of a high-performance optical system for angular position measurement: optical and electronic strategies for uncertainty reduction [Articolo su rivista]
Rovati, Luigi; M., Bonaiuti; Pavan, Paolo
abstract

A high-performance optical system to reduce measuring errors and uncertainty in angular encoders is presented. We propose a novel reading optical head, which exploits a lens system to improve the speed of the beam crossing the photodelector and a quadrant photodiode to perform a zero-crossover acquisition of the timing information.


2005 - Instrumentation and calibration protocol for a continuous wave NIRS oximeter [Relazione in Atti di Convegno]
G., Salvatori; K. L., Suh; R. R., Ansari; Rovati, Luigi
abstract

We describe a continuous wave near infrared oximeter and its calibration protocol. The system performs quantitative assessments exploiting precise absorption measurements close to the absorption peak of the water: 975nm. We report the procedures and the systematic in vitro tests adopted to characterize and calibrate the entire system. A final stability analysis is reported to validate the instrumentation


2005 - Non-invasive in vivo infrared laser spectroscopy to analyse endogenous oxy-haemoglobin, deoxy-haemoglobin, and blood volume in the rat CNS [Articolo su rivista]
Crespi, F.; Bandera, A.; Donini, M.; Rovati, Luigi
abstract

Oxy-haemoglobin (HbO2) and deoxy-haemoglobin (Hb) are chromophores present in biological tissues. Near infrared spectroscopy (NIRS) is a non-invasive methodology based on the low extinction coefficient of tissue in the near infrared region. NIRS can be used to measure changes in the concentration of these chromophores, i.e., haemoglobin, in muscular tissue. In the present work, NIRS has been used for the non-invasive monitoring of HhO2, Hb, and blood volume (V: representing total haemoglobin, i.e., HhO2 + Hb) in vivo in the whole rat brain. This has been performed by means of prototype instrumentation based on optic fibre probes placed in contact with the head of anaesthetised rats held in a stereotaxic frame. A preliminary test of the instrument has been performed on human muscle, i.e., lateral gastrocnemius, in order to evaluate the ability of the instrument to detect oxygenation changes. Afterwards, the effects of pharmacological treatments, such as sytemic amphetamine and nicotine treatments on the CNS have been detected.


2005 - Optical Schemes for Polarimetric Glucose Sensing Analyzed by the Anatomical Eye Model of Navarro [Relazione in Atti di Convegno]
Rovati, Luigi; Ansari, R. R.
abstract

We analyze three different optical schemes to access the human eye to enable glucose sensing. These methods are analyzed theoretically. A simulation based upon the anatomical eye model of Navarro is presented.


2005 - Synchronous phase to voltage converter for true-phase polarimeters [Articolo su rivista]
M., Ruggeri; G., Salvatori; Rovati, Luigi
abstract

This paper describes a front-end electronics designed to process the signals generated by a true-phase polarimeter. The design of the network is oriented to minimize the phase angle measurement uncertainty. The circuit has been accordingly developed and tested in operation. Exploiting a precise analogue phase-to-voltage converter based on a synchronous detection scheme, the network exhibits a phase angle measurement uncertainty less than 0.35 mdeg. The circuit exhibits excellent rejection of uncorrelated noise, disturbances, offsets and harmonics.


2004 - Autofluorescence methods in ophthalmology [Articolo su rivista]
Rovati, Luigi; Docchio, F.
abstract

An overview of the fluorophores of the eye, the methods used to measure ocular fluorescence, and the existing or ready-to-market instrumentation for the early diagnosis and monitoring of ophthalmic pathologies is presented. Emphasis is given to the impact that a more detailed knowledge of the fluorophores of the eye, their age and pathology relationship, and the considerable technology-driven progress in optical devices and components has had on the development of new compact yet powerful instruments for population screening and for patient follow-ups, using fluorometry alone or in combination with other optical techniques such as light scattering. (C) 2004 Society of Photo-Optical Instrumentation Engineers.


2004 - Design and performance of a wide-bandwidth and sensitive instrument for near-infrared spectroscopic measurements on human tissue [Articolo su rivista]
Rovati, Luigi; Bandera, A; Donini, M; Salvatori, G; Pollonini, L.
abstract

The article describes an instrument designed to perform in vivo near-infrared spectroscopic measurements on human tissues. The system integrates five continuous-wave laser diode sources emitting in the near-infrared spectral region and a low-noise detection system based on an avalanche photodiode. The optical probe is based on a compact, reliable, and low-cost fiber based system with four quantitative measuring points. The excellent sensitivity of the instrument allows one to perform quantitative assessments of the hemoglobin concentration exploiting precise absorption measurements close to the absorption peak of the water: 975 nm. Moreover, a good signal to noise ratio is obtained also at a high acquisition rate, allowing us to follow rapid changes in oxidative metabolism. The system bandwidth is selectable within the range 2.3-27 Hz, i.e., 20 channels (five chromatic and four spatial channels) can be acquired 27 times for each measuring second, whereas the system amplification can be set to measure optical density ranging from 3.5 to 8.5. A prototype version of the instrument has been realized and characterized.


2004 - Design and performance of an ophthalmic instrument for dynamic light scattering and fluorescence measurements in ocular tissues [Relazione in Atti di Convegno]
Rovati, Luigi; L., Pollonini; R., Ansari
abstract

The paper describes an ophthalmic instrument designed to perform in-vivo dynamic light scattering and autofluorescence measurements on ocular tissues. We modified a commercial scanning ocular fluorometer, to include both techniques in the same scanning unit. The resulting optical system provides both dynamic light scattering and autofluorescence measurements from the same ocular volume, which can be located in each section of the ocular axis from the cornea to the retina. In this paper, the instrument is described and in-vitro/in-vivo measurements are presented.


2004 - Design of an optical sensor for surface roughness measurements of wood based panels [Relazione in Atti di Convegno]
Rovati, Luigi; L., Pollonini; M., Zanasi; D., Sivieri; M., Badiali
abstract

Surface inspection methods are strategic to accurately monitor the quality of the wood panel surface. Optical techniques represent a unique solution to develop inexpensive, simple, and compact, solid-state sensors. In this paper we propose a preliminary study oriented to investigate the use of light scattering technique to perform online measurements of wood panel surface roughness


2004 - Diode Zener Feedback Preamplifier for Zero-Crossover Optical Encoders [Relazione in Atti di Convegno]
G., Salvatori; Rovati, Luigi
abstract

A novel preamplifier system to improve the performance of zero-crossover optical encoders is presented. The network is based on a low-noise operational amplifier with a Zener diode feedback. We propose to exploit the non-linear characteristic of this network to reduce the angular measurement uncertainty. The circuit has been accordingly developed and tested in operation.


2004 - Functional cerebral activation detected by an integrated system combining CW-NIR spectroscopy and EEG [Relazione in Atti di Convegno]
Rovati, Luigi; Fonda, Sergio; Bulf, Luca; Ferrari, Renata; Biral, Giampaolo; Salvatori, Giorgia; Bandera, Andrea; Corradini, Matteo
abstract

The aim of this study is to explore the possibility of correlating hemodynamic changes and neural activities in the brain by using an integrated system combining Near Infrared Spectroscopy (NIRS) and electroencephalographic activity (EEG). We present brain hemodynamic changes and EEG recordings obtained from four volunteers during the performance of two different sequential thumb-finger opposition tasks, with and without a related mental activity. The optical and electrical signals were recorded simultaneously on the subject forehead. The coupling of the two systems could be useful to demonstrate correlation between cognitive paradigms and hemodynamic signals.


2004 - Near-infrared oxymeter prototype for noninvasive analysis of rat brain oxygenation [Relazione in Atti di Convegno]
Francesco, Crespi; Maurizio, Donini; Andrea, Bandera; Christian, Heidbreder; Giorgia, Salvatori; Rovati, Luigi
abstract

The feasibility of non-invasive analysis of brain activities was studied in the attempt to overcome the major limitation of actual in vivo methodologies i.e. invasiveness. Optic fibre probes were used as optical head of a novel, highly sensitive near infrared continuous wave spectroscopy (CW-NIR) instrument. This prototype was designed for non-invasive analysis of the two main forms of haemoglobin: oxy-haemoglobin (HbO2) and deoxy-haemoglobin (Hb), chromophores present in biological tissues. It was tested in peripheral tissue (human gastrocnemius muscle) and then reset to perform measurement on rat brain. In animal studies, the optical head was firmly placed using stereotaxic apparatus upon the sagittal line of anaesthetised adult rat's head, without any surgery. Then pharmacological treatments with saline (300µl s.c.) amphetamine (2mg/kg) or nicotine (0.4mg/kg) were performed. Within 10-20 min amphetamine substantially increased HbO2 and reduced Hb control levels. Nicotine produced a rapid initial increase followed by a decrease of HbO2. In contrast to amphetamine, nicotine treatment also reduced Hb and blood volume. These results support the capacity of our CW-NIR prototype to measure non-invasively HbO2 and Hb levels in the rat brain, markers of the degree of tissue oxygenation, index of blood level then of the state of brain metabolism.


2004 - New optical scheme for a polarimetric-based glucose sensor [Articolo su rivista]
R. R., Ansari; S., Bockle; Rovati, Luigi
abstract

A new optical scheme to detect glucose concentration in the aqueous humor of the eye is presented. The ultimate aim is to apply this technique in designing a new instrument for, routinely and frequently, noninvasively monitoring blood glucose levels in diabetic patients without contact (no index matching) between the eye and the instrument. The optical scheme exploits the Brewster reflection of circularly polarized light off of the lens of the eye. Theoretically, this reflected linearly polarized light on its way to the detector is expected to rotate its state of polarization, owing to the presence of glucose molecules in the aqueous humor of a patient's eye. An experimental laboratory setup based on this scheme was designed and tested by measuring a range of known concentrations of glucose solutions dissolved in water. (C) 2004 Society of Photo-Optical Instrumentation Engineers.


2004 - Non invasive evaluation of pigment dispersion syndrome using dynamic light scattering. [Abstract in Rivista]
L., Pollonini; R. R., Ansari; A., Pasquali; Rovati, Luigi; L., Quaranta
abstract

Purpose: The goal of this pilot study is to evaluate patients affected by pigment dispersion syndrome (PDS) using the technique of dynamic light scattering (DLS) in the aqueous humor (AH). Methods: Dynamic light scattering is a technique able to detect abnormalities at molecular level in ocular tissues. DLS particle size measurements are performed in the AH. 16 patients affected with PDS (16 eyes; mean age: 53.3{+/-}14.1; gender: 8 male, 8 female) and 15 normal subjects (15 eyes; mean age: 64.1{+/-}15.2; gender: 3 male, 12 female) were evaluated for the study. Results: The measuring range of diameter is between 50 and 2000 nm. The mean diameter of particles in PDS eyes was found to be 761{+/-}638 nm, whilst in normal eyes was 135{+/-}193 nm (t-Student test: P=0.009). DLS measurements showed a significantly higher prevalence of particles with a mean diameter under 500nm in normal eyes when compared with PDS eyes (93.3% normal eyes vs 47% in PDS eyes; Fisher's exact test: P=0.013). Conclusions: Larger size particles were detected in PDS eyes compared with normal cohorts. DLS can be used to detect pigment dispersion syndrome non invasively.


2004 - Noninvasive monitoring of glucose concentration through the aqueous humor [Abstract in Rivista]
S., Boeckle; R. R., Ansari; Rovati, Luigi; J. F., King; K. I., Suh
abstract

Purpose:Development of a new optical sensor for measuring blood glucose levels noninvasively to replace the current finger-prick method routinely used by diabetics. Methods:We have developed a new optical scheme for a polarimetric-based glucose sensor. Such a sensor is intended to noninvasively measure the glucose content of the aqueous humor, which is highly correlated to the blood glucose concentration in the body. The polarimetric measurement method is based upon optical activity of glucose, i.e., the plane of polarization of a polarized light beam is rotated when propagating through a glucose solution. The amount of polarization rotation is proportional to the glucose concentration, which therefore can be determined. Our new optical scheme applies Brewster reflection of incident circularly polarized light off the eye lens. The incoming light is not affected by optical activity. However, the back reflected linearly polarized light is rotated while crossing the aqueous humor of the eye. From this polarization rotation of the reflected light the glucose concentration in the aqueous humor can be determined. Results:In this proof-of-concept study the linearity between glucose concentration and polarization rotation is investigated with glucose concentrations ranging from 0 to 1000 mg/dl. The obtained data show a correlation coefficient of 0.986. Further, we have tested our approach on a model of the human eye, which has been designed in our lab. In this eye model the cornea has been modeled by a contact lens, the aqueous humor by solutions of glucose in distilled water, and the crystallin lens by a lens implant. Conclusions:The results show good linearity of the measurement system. However, detailed experimental work is needed to demonstrate its full applicability in human patients.


2004 - Nonlinear feedback preamplifier for optical trigger circuits [Articolo su rivista]
Rovati, Luigi; Salvatori, G.
abstract

A nonlinear preamplifier system to improve the performance of a zerocrossover optical trigger circuit is presented. The network is based on a low-noise operational amplifier with a Zener diode feedback. It is proposed to exploit the nonlinear characteristic of this network to reduce timing measurement uncertainty. Accordingly the circuit has been developed and tested in operation.


2004 - Simulation of optical path and volume-under-test calculation in an integrated dynamic light scattering and autofluorescence device [Relazione in Atti di Convegno]
Luca, Pollonini; Rafat R., Ansari; Rovati, Luigi
abstract

We have developed a non-invasive diagnostic instrument based on a scanning fluorophotometer integrating autofluorescence and dynamic light scattering techniques. The device makes a scan along the optical axis of the eye. In a DLS measurement, it is extremely important to precisely define the position of the volume-under-test inside the eye and its effective volume. In this work, a specific optical computer aided design tool based on the Navarro's model of the human eye is used to simulate the optical path of the DLS laser beams and to calculate position and size of the volume-under-test.


2003 - A NOVEL TISSUE OXYMETER COMBINING THE MULTIDISTANCE APPROACH WITH AN ACCURATE SPECTRAL ANALYSIS [Relazione in Atti di Convegno]
Rovati, Luigi; Bandera, A.; Donini, M.; Pollonini, L.
abstract

In this paper a novel optical tissue oxymeter thatintegrates the multidistance approach and the evaluation of thedifferential pathlength qloiting the absorption features of waferis presented This system tukes advantage from the peculiarities ofthese techniques to extract the scatterirrg and the absorptioncoeficient reducing errors introduced by the heterogeneousstructure of the tissue and improving the signal-to-noise ratio.


2003 - Design of a high-performance optical system for angular position measurement: optical and electronic strategies for uncertainty reduction [Relazione in Atti di Convegno]
Rovati, Luigi
abstract

A high-performance optical system to reduce measuring errors and uncertainty in angular encoders is presented. We propose a novel reading optical head, which exploits a lens system to improve the speed of the beam crossing the photodetector and a quadrant photodiode to perform a zero-crossover acquisition of the timing information.


2003 - Glucose sensing using the Brewster reflection: polarimetric ray-tracing based upon an anatomical eye model [Relazione in Atti di Convegno]
Boeckle, S.; Rovati, Luigi; Ansari, R. R.
abstract

In this paper we present theoretical analysis to support the polarimetric approach for glucose detection in the human eye applying Brewster reflection off the ocular lens. The theoretical eye model of Navarro, which is based upon anatomical data, was used to perform ray-tracing, whereas the electromagnetic and polarization parameters of light propagation through the eye-media were calculated. The errors in glucose concentration determination due to refraction and deviation from the ideal optical path were calculated under different conditions. Effects of using incident linearly and circularly polarized light and variation of intersection condition of the incoming light beam with the anterior corneal surface were taken into consideration. Calculations were performed for a wide spectral range by applying dispersion curves for the eye-media. These simulations show the potential and the limits of the proposed optical approach.


2003 - Pigment dispersion syndrome (PDS) assessment by dynamic light scattering [Relazione in Atti di Convegno]
Pollonini, L.; Rovati, Luigi; Pasquali, A.; Franzoni, A.; Quaranta, L.
abstract

Pigment dispersion syndrome and pigmentary glaucoma areinvestigated by a scanning instrument based on dynamic lightscattering technique. The measurements are oriented to evaluatethe various conjectures about the pathogenesis of pigmentaryglaucoma and to establish a diagnostic tool that may be used foran early detection of this type of glaucoma.


2003 - Polarimetric glucose sensing using Brewster reflection applying a rotating retarder analyzer [Relazione in Atti di Convegno]
Beckle, S.; Rovati, Luigi; Ansari, R. R.
abstract

Previously, we proposed a polarimetric method, that exploits the Brewster-reflection with the final goal of application to the human eye (reflection off the eye lens) for non-invasive glucose sensing. The linearly polarized reflected light of this optical scheme is rotated by the glucose molecules present in the aqueous humor, thus carries the blood glucose concentration information. A proof-of-concept experimental bench-top setup is presented, applying a multi-wavelength true phase measurement approach and a rotating phase retarder as an analyzer to measure the very small rotation angles and the complete polarization state of the measurement light.


2003 - Unsupervised corrections of unknown chromatic dominants using a Brownian-path-based retinex algorithm [Articolo su rivista]
Rizzi, A; Marini, D; Rovati, Luigi; Docchio, F.
abstract

An experimental analysis of chromatic equalization based on a new implementation of the Retinex algorithm is presented. The experiments are carried out on a colored Mondrian patchwork illuminated with different commercial light sources and on synthetic images generated with a photometric ray tracer using different illuminants. Regarding the Mondrian patchwork, the spectral characteristics of the bulbs and the reflected light from each patch are measured using a commercial spectrometer From the measured data, synthetic images of the patchwork with different illuminants are created and processed by the Retinex algorithm. The chromatic correction capabilities of the Retinex implementation have been measured and compared with unfiltered values and with the results of another Retinex implementation and classic color equalization algorithms. Results show that Retinex performs an unsupervised color correction without requiring any information about the spectral composition of the illuminant.


2002 - A system for the inspection and quality control of glass slabs [Articolo su rivista]
Rovati, Luigi; L., Pollonini; F., Docchio
abstract

This article describes an innovative interferometric system for the inspection and quality control of glass slabs. The instrument exploits a self-mixing superluminescent diode scheme to improve the interferometric signal and to reject typical noise and electromagnetic interference existing in industrial environments. Various instrumental aspects and performance issues are discussed. Experimental activities demonstrate a system measuring range of 4.5 mm with a relative measurement uncertainty of less than 2%. Whereas, the measuring stability was measured to be about 2.5 mum over 20 min.


2002 - Dynamic light scattering and natural fluorescence measurements in healthy and pathological ocular tissues [Relazione in Atti di Convegno]
Pollonini, L.; Rovati, Luigi; Ansari, R. R.
abstract

Dynamic light scattering (DLS) and autofluoresence (AF) are two promising optical diagnostic techniques for use in ophthalmology. In this paper the DLS and AF are integrated in one instrument and applied to study healthy and pathological ocular tissues to detect changes at the molecular level. Measurements performed on 17 patients (age range 20-80 years) are presented. Out of these, 7 patients were healthy normals, 10 had glaucoma and the two oldest patients had both glaucoma and cataracts.


2002 - Microcontroller-based front-end electronics for simultaneous measurements of dynamic light scattering and natural fluorescence [Relazione in Atti di Convegno]
Pollonini, L.; Pasquali, A.; Rovati, Luigi; Ansari, R. R.
abstract

A digital control unit for use with a new integrated instrument for dynamic light scattering and natural fluorescence measurements is presented. This unit, based on a microcontroller (Microchip PIC16F877), process signals from an optical head and controls instrument functions. The microcontroller internal counters are used to perform real- time photon counting measurement by processing the TTL signals obtained from the photodetectors. The new system provides reliable and simultaneous DLS and AF measurements from the same ocular volume located from the cornea to the retina.


2002 - Polarimetric glucose sensing using the Brewster-reflection off the eye lens: theoretical analysis [Relazione in Atti di Convegno]
Boeckle, S.; Rovati, Luigi; Ansari, R. R.
abstract

An important task of in vivo polarimetric glucose sensing is to find an appropriate way to optically access the aqueous humor of the human eye. In this paper two different approaches are analyzed theoretically and applied to the eye model of Le Grand. First approach is the tangential path of Cote et al., and the second is a new scheme of this paper of applying Brewster reflection off the eye lens.


2001 - A PC-controlled non-incremental distance meter based on a comb-spectrum combined with a frequency modulated continuous wave interferometer [Relazione in Atti di Convegno]
Rovati, Luigi
abstract

In this paper, a PC-controlled nonincremental interferometer that integrates frequency-modulated continuous wave (FMCW) and dispersive comb spectrum (DCS) techniques is presented. This system takes advantage of the wide measuring range of the FMCW technique and of the high resolution of the DCS technique. The system prototype presented in this paper performs measurements over a range of 30 mm with an accuracy of about 600 nm. The proposed combined interferometer is expected to also have applications in biomedical frameworks


2001 - Celestial and terrestial tele-ophthalmology: A Health Monitoring Helmet for Astronaut/Cosmonaut and General Public Use [Relazione in Atti di Convegno]
R. R., Ansari; Rovati, Luigi; J., Sebag
abstract

A goggles-like head-mounted device equipped with several non-invasive techniques for quantitative medical evaluation of the eye, skin, and brain is envisioned for monitoring the health of astronauts and cosmonauts during long-term space travel and exploration. Real-time non-invasive evaluation of the different structures within these organs will provide indices of the health of these organs, as well as the entire body. The techniques such as dynamic light scattering (for the early detection of cataracts to evaluate effects of cosmic radiation), corneal autofluorescence (to assess extracellular matrix biology (e.g., diabetes), optical polarization (of aqueous fluid to evaluate serum chemistry), laser Doppler velocimetry (of retinal, optic nerve, and choroidal blood flow to assess ocular as well as central nervous system blood flow), reflectometry/oximetry (for oxygen metabolism), optical coherence tomography (for retinal microstructure), and possibility scanning laser technology for intraocular imaging and scanning will be integrated into this compact device.


2001 - Development of a novel noninvasive sensor for determination of blood glucose concentration [Relazione in Atti di Convegno]
Boeckle, S.; Rovati, Luigi; Ansari, R. R.
abstract

Optical methods represent the most promising techniques to perform non-invasive glucose detection. Glucose concentration in the aqueous humor closely mimics glucose levels in the blood and therefore non-invasive optical measurement of glucose can be performed by an optical beam crossing the eye anterior chamber. We propose a polarimetric method that exploits the Brewster-reflection of circularly polarized light on the lens of the eye. After reflection, the resulting linearly polarized light is subject to rotation by the glucose in the aqueous humor and thus carries the concentration information. A preliminary experimental setup, using glucose samples in a beaker, was realized and investigated.


2001 - Dynamic light scattering and natural fluorescence measurements of the corneal tissue [Relazione in Atti di Convegno]
Pollonini, L.; Rovati, Luigi; Ansari, R. R.
abstract

Dynamic light scattering (DLS) and autofluorescence (AF) are non-invasive diagnostic techniques that can monitor changes at the molecular level in ocular tissues. In the present study, we demonstrate as simultaneous measurements of autofluorescence and dynamic light scattering on the corneal tissues can be performed using a novel specifically designed instrument. The integrated instrument takes advantage of the singular techniques by improving the measurement quality and the reliability of the diagnosis. Preliminary tests on volunteers show promise in relation to possible use in the clinical practice.


2001 - Integrated instrument for dynamic light scattering and natural fluorescence measurements [Relazione in Atti di Convegno]
Rovati, Luigi; Pollonini, L.; Ansari, R. R.
abstract

Over the past two decades, great efforts have been made in ophthalmology to use optical techniques based on dynamic light scattering and tissue natural fluorescence for early (at molecular level) diagnosis of ocular pathologies. In our previous studies, the relationship between the corneal AF and DLS decay widths of ocular tissues were established by performing measurements on diabetes mellitus patients. In those studies, corneal AF mean intensities were significantly correlated with DLS decay width measurements for each diabetic retinopathy grade in the vitreous and in the cornea. This suggested that the quality of the diagnosis could be significantly improved by properly combining these two powerful techniques into a single instrument. Our approach is based on modifying a commercial scanning ocular fluorometer (Fluorotron Master, Ocumetrics Inc., CA, USA) to include both techniques in the same scanning unit. This configuration provides both DLS and AF real time measurements from the same ocular volume: they can be located in each section of the optical axis of the eye from the cornea to the retina. In this paper, the optical setup of the new system is described and preliminary in-vitro and in-vivo measurements are presented.


2001 - Novel optical sensor for the measurement of surface texture [Articolo su rivista]
Tomassini, P.; Rovati, Luigi; Sansoni, G.; Docchio, F.
abstract

In this article we describe a novel optical sensor designed to measure surface texture, i.e., the roughness and waviness. The system integrates a surface profiler and a light scattering unit in a compact setup suitable for industrial applications. This sensor could represent a unique surface inspection tool to be integrated in grinding stations used for reconditioning rolls for milling. The spatial wavelength measuring range for waviness is 1-100 mm, whereas the amplitudes of the measured defects can be in the range 200 nm-5 μm for waviness and 100 nm-1.5 μm for roughness. The system exhibits a measurement uncertainty of less than 2% of the measuring range. The industrial version of the sensor has been realized and characterized in field.


2001 - Rotating polarizer and rotating retarder plate polarimeters: comparison of performances [Relazione in Atti di Convegno]
Pelizzari, S.; Rovati, Luigi; De Angelis, C.
abstract

Rotating polarizer and rotating retarder plate polarimeters are widely used in high-resolution polarimetry, for example in remote sensing, fiber optic measurements and biomedics; as a consequence the analysis of the performances of these devices is very important from the instrumental point of view. To compare the two methods, we developed a synchronous polarimeter based on a mechanically rotating stage, where a rotating Glan-Thompson linear polarizer or a wave retarder can be easily mounted. A specific design allows to acquire synchronously the intensity signals digitally process the data to extract the polarization Stokes parameters. We investigate the two cases along with their impact on measurement techniques. Performance curves are shown for various polarization input parameters and light levels. Specifically, we address issues concerning the accuracy and the systematic and statistical measuring errors. Moreover, computer simulations and measurement results are presented and discussed.


2000 - A Novel Optical Stylus Probe for the Measurement of Surface Roughness and Waviness [Relazione in Atti di Convegno]
P., Tomassini; R., Rodella; Rovati, Luigi; S., Sansoni; F., Docchio
abstract

A Novel Optical Stylus Probe for the Measurement of Surface Roughness and Waviness


2000 - Determination of the interferents in blood serum through a novel solid-state colorimeter [Articolo su rivista]
Rovati, Luigi; Docchio, F.
abstract

The quality of the clinical-chemistry analysis of blood serum is greatly affected by interfering substances contained in the sample. At present, skilled laboratory personnel select specimens which can be processed by the analyser. Selection is performed by visual inspection of the serum colour. To reduce laboratory labour costs and risk of infections, we developed an inexpensive, simple and compact solid-state colorimeter to determine concentrations of interferents. This sensor can be integrated into modern clinical-chemistry analysers. The determination of concentrations of interferents is based on the measurement of the extinction coefficients of the serum sample at four different wavelengths. In this paper, this instrument and its performance are presented.


2000 - Interferometric distance sensors [Relazione in Atti di Convegno]
U., Minoni; Rovati, Luigi; F., Docchio
abstract

Optical interferometry is a well-known technique successfully used to perform displacementmeasurements in the industrial framework. In general, commercial devices use incrementalinterferometry: to measure a displacement it is necessary to fix a reference position and tocarefully displace a suitable reflector (or some other optical component of the interferometer)from that position to the final one. This must be done avoiding any optical misalignment thatcould result in a loss of the interference signal and therefore of the measure. An incrementalinterferometric displacement measurement always implies a precise device to move the reflector,and a counter to keep trace of the number of periods of interference fringes that the photodetectorhas detected during the movement. The main advantage of this measurement technique is a verylow measurement uncertainty (down to some fractions of λ in commercial meters) coupled to anextended range (up to tens of meters). In general, therefore, an interferometric system is the rightchoice when both high accuracy and a long measuring range are required.A number of industrial needs cannot be successfully met by incremental interferometers,especially in the fields of dimensional gauging of surfaces, robot monitoring and characterization,autonomous vehicle controls, etc.. In fact in these fields the quantity to be measured is distanceand not displacement. Taking as an example the problem of industrial robot calibration, the idealmeasuring tool should be able to freely follow the robot end-effector, to measure the actualposition along an arbitrary trajectory. An absolute (i.e. non-incremental) distance meter pointingto the robot manipulator could accomplish this task. Interferometric sensors have great potentialin performing non-incremental measurement at a very high degree of accuracyThe following paragraphs describe the available interferometric techniques to perform nonincrementalmeasurements outlining the principle of operation and the applicability to industrialcases. At the end a comparison of the investigated techniques is given.


2000 - Monitoring Astronaut Health Through the Eye [Relazione in Atti di Convegno]
R. R., Ansari; B. S., Singh; Rovati, Luigi; F., Docchio; J., Sebag
abstract

A user friendly goggles-like head-mounted device equipped with a suite of instruments for several non-invasive and quantitative medical evaluation of the eye, skin, and brain is desired for monitoring the health of astronauts during space travel and exploration of neighboring and distant planets. Real-time non-invasive evaluation of the different structures within the above organs can provide indices of the health of not just these organs, but the entire body. The techniques such as dynamic light scattering (for the early detection of uveitis, cholesterol levels, cataract, changes in the vitreous and possibly Alzheimer's disease), corneal autofluorescence (to assess extracellular matrix biology e.g., in diabetes), optical activity measurements (of anterior ocular fluid to evaluate blood-glucose levels), laser Doppler velocimetry (to assess retinal, optic nerve, and choroidal blood flow), reflectometry/oximetry (for assessing ocular and central nervous system oxygen metabolism), optical coherence tomography (to determine retinal tissue microstructure) and possibly scanning laser technology (for intraocular tissue imaging and scanning) will be integrated into this compact device. Skin sensors will also be mounted on the portion of the device in contact with the periocular region. This will enable monitoring of body temperature, EEG, and electrolyte status. This device will monitor astronaut health during long-duration space travel by detecting aberrations from pre-established "norms", enabling prompt diagnosis and possibly the initiation of early preventative/curative therapy. The non-invasive nature of the device technologies permits frequent repetition of tests, enabling real-time complete crew health monitoring. This device may ultimately be useful in tele-medicine to bring modern healthcare to under-served areas on Earth as well as in so-called "advanced" care settings (e.g. diabetes in the USA).


2000 - Optimum preamplification and shaping of signals delivered by photodetectors without internal amplification: a theoretical analysis [Articolo su rivista]
Rovati, Luigi
abstract

The use of photodetectors without internal amplification is an appealing choice in the design of low-cost solid-state optical instrumentation. However, once photodiodes are used in the detection unit, the instrument sensitivity is related not only to the photodetector characteristics, but mainly to the front-end electronics noise performance. Therefore, great care has to be taken in the design of the preamplification and shaping electronics in order to minimize their noise contribution. The present paper introduces, from the theoretical point of view, the optimum front-end electronics to process signals delivered by photodetectors without internal amplification. In the analysis performed, with simple formalism, the optimum signal-to-noise ratio and the minimum detectable signal have been calculated. Moreover some practical realizations, which approximate the optimum signal processor, are presented


2000 - Tomografia ottica coerente [Voce in Dizionario o Enciclopedia]
Rovati, Luigi
abstract


1999 - A novel low-coherence sensor for industrial applications based on a self-mixing super-luminescent diode [Relazione in Atti di Convegno]
Rovati, Luigi; F., Docchio
abstract

A novel low-coherence sensor for industrial applications based on a self-mixing super-luminescent diode


1999 - Autofluorescence of ocular tissues: a promising diagnostic technique in ophthalmology [Relazione in Atti di Convegno]
Franco, Docchio; Rovati, Luigi
abstract

In the past, ocular diagnosis through fluorometric systems has been mainly based onto exogenous agents. Recently, a number of diagnostic techniques has been proposed for diagnosis of ocular pathologies, which are based upon the naturally occurring fluorescent emission of ocular tissues. In this paper, we discuss major advantages and drawbacks of these techniques, focusing in particular our attention on a novel diagnostic technique based onto autofluorescence of corneal tissue.


1999 - Design and performance of a low-coherence sensor for industrial applications based on a self-mixing superluminescent diode [Relazione in Atti di Convegno]
Rovati, Luigi; Docchio, F.
abstract

In this paper a novel low-coherence sensor based on a self- mixing super-luminescent diode (SM-SLD) is described. A commercial low-cost super-luminescent diodes (SLD) driven at constant current is used as low-coherence source. In the same case of the SLD there is a photodiode generally used to monitor the optical power at the emitting junction back-face. In the SM-SLD technique, this photodiode is exploited to detect the interference signal. Hence, the interference signal is optically amplified by the high-gain active medium. The sensor has been properly designed to work in industrial environments and is suitable for measurement of semitransparent slabs thickness, i.e. glass, Plexiglas, polyethylene, etc. Measurements carried out on glass slabs show a measuring range of 15 mm and a linearity error and stability of 1.3 micrometer and 1.6 micrometer respectively.


1999 - Design and performance of an optical sensor for the measurement of surface roughness and waviness [Relazione in Atti di Convegno]
Franco, Docchio; Umberto, Minoni; Roberto, Rodella; Rovati, Luigi; Valeriano, Corallo
abstract

We developed a novel sensing equipment for the measurement of roughness and waviness of rolls during grinding. The sensors can operate on different materials, in harsh conditions, and measurements can be performed on-line, in a non-contact fashion. The sensing equipment makes use of a commercial triangulation sensor, suitably integrated with an additional optical head. The triangulator produces two signals, respectively proportional to the distance from the target surface and to the intensity of the scattered light. The optical head consists of two photodiodes placed in the proximity of the excitation beam and produces a signal proportional to the intensity of the light scattered at smaller angle. The distance signal is used to extract the waviness information, whereas its combination with the intensity of the light scattered both at large and small angles is necessary to derive the roughness information. The resulting sensor is able to measure waviness and roughness in the spatial wavelength ranges of 1 mm divided by 100 mm and 0.1 mm divided by 1 mm respectively; with height range of the defects equal to 200 nm divided by 5 micrometer. The measurement uncertainty is less than 2.5% and the linearity is 1% of the measuring range.


1999 - Development of an optical sensor for the measurement of surface roughness and waviness [Relazione in Atti di Convegno]
F., Docchio; U., Minoni; R., Rodella; Rovati, Luigi
abstract

Development of an optical sensor for the measurement of surface roughness and waviness


1999 - Dispersive comb-spectrum interferometer: metrological characterization [Articolo su rivista]
U., Minoni; Rovati, Luigi; M., Bonardi; F., Docchio
abstract

The paper reports results of an investigation on the main measurement uncertainty sources in a novel distance meter based on dispersive comb-spectrum interferometry. The light source is a commercial laser diode operating at 670 nm driven under the threshold condition, and emitting a beam with a comb-shaped spectrum. Sensitivity of the measurement to the operating conditions has been evaluated. Results from an experimental activity aimed at characterizing the laser and to measure the performance of a prototype implementation are also presented. The system can perform unambiguous nonincremental distance measurements over a range of 0.8 mm with a total uncertainty of about 1.5 ?m


1999 - High-performance front-end electronics for frequency-modulated continuous-wave interferometrs [Articolo su rivista]
Rovati, Luigi; U., Minoni
abstract

A high-performance analog electronic circuit for processing the signal from an absolute distance meter based on a frequency-modulated continuous-wave (FMCW) interferometer is presented. The front-end electronics includes a derivative block followed by a the time-variant baseline restoration of the photodetector current. A high signal-to-noise ratio is ensured by avoiding the use of a resistive transimpedance preamplifier and subsequent voltage processing. The paper details the electrical scheme of the preprocessing chain as well as the experimental results from an actual prototype of a distance meter


1999 - Low-noise differentiator preamplifier for photogenerated signals [Articolo su rivista]
Rovati, Luigi; Docchio, F.
abstract

A low-noise preamplifier to perform a derivative of photogenerated signals is proposed. The novel structure is based on an inductive feedback preamplifier which performs preamplification and a derivative of the photogenerated current in a single stage. A breadboard circuit implementation and noise measurements are presented. Comparative noise measurements show that the proposed architecture is competitive with the classical differentiator preamplifier


1999 - Low-noise front-end electronics for solid-state fluorometers [Articolo su rivista]
Rovati, Luigi; Franco, Docchio
abstract

New steady-state fluorometric systems are based on solid state-optoelectronic components such as blue light-emitting diodes, avalanche photodiodes, and standard photodiodes. In the latter case, the noise performance of the front-end electronics limits the sensitivity of the instrumentation. However, signal detection performed by standard photodiode is appealing in low-cost applications. In this article, a low-noise electronic setup which processes the signal from photodetectors without internal amplification is presented. Low-noise preamplification and optimal signals shaping allow to minimize the fluorometric measurement uncertainty. The circuit has been accordingly developed and tested in operation. Using a low-cost silicon photodiode, a minimum equivalent noise power less than 1 pW/ has been obtained at a shaping time of 200 µs. The circuit exhibits excellent rejection to continuous ambient light and partially suppresses the alternating components.


1999 - Self-mixing superluminescent diode optical tomography [Relazione in Atti di Convegno]
Rovati, Luigi; Franco, Docchio
abstract

Self-mixing superluminescent diode optical tomography


1999 - Signal enhancement and satellite subpeaks degradation in self-mixing super luminescent diode optical tomography [Relazione in Atti di Convegno]
Rovati, Luigi; F., Docchio
abstract

Signal enhancement and satellite subpeaks degradation in self-mixing super luminescent diode optical tomography


1998 - Absolute distance measurement using comb-spectrum interferometry [Articolo su rivista]
Rovati, Luigi; U., Minoni; M., Bonardi; F., Docchio
abstract

A measurement technique is proposed based on dispersive interferometry using a comb-spectrum source: dispersive comb-spectrum interferometry (DCSI). The configuration proposed processes the Michelson interferometer output by a dispersive grating in the Littrow configuration. Using a commercial low-cost laser diode source, the non-ambiguity measuring range was measured to be 1.6 mm, whereas the maximum permissible working distance, including ambiguity was measured to be 1.2 cm. The linearity error and stability were measured to be and 32 nm, respectively.


1998 - Absolute distance meter based on a frequency-modulated laser diode [Articolo su rivista]
U., Minoni; Rovati, Luigi; F., Docchio
abstract

This article describes a distance measuring instrument based on a frequency-modulation continuouswave interferometer implemented in a compact setup suitable for industrial applications. Theprototype uses a visible laser diode that is frequency-modulated with a triangular wave form.Measurements carried out with a cooperative target show a measuring range from 130 to 300 mmwith a relative accuracy of 1200 ppm.


1998 - Analog signal pre-processing for performance enhancement of a distance meter based on frequency-modulated continuous-wave interferometry [Relazione in Atti di Convegno]
Rovati, Luigi; U., Minoni
abstract

A method for the processing of signal from an absolute distance meter based on a frequency-modulated continuous-wave (FMCW) interferometer is presented. FMCW is implemented using a laser diode driven by a current waveform obtained as the superposition of a triangular signal to a bias current kept well above the diode lasing threshold. The analog signal pre-processing includes a derivative block followed by the time-variant baseline restoration of the photodetector current. A high signal-to-noise ratio is ensured by avoiding the use of a resistive transimpedence preamplifier and subsequent voltage processing. The paper details the scheme of the pre-processing chain as well as the experimental results from an actual prototype of a distance meter


1998 - Corneal autofluorescence in presence of diabetic retinopathy [Relazione in Atti di Convegno]
Rovati, Luigi; Franco, Docchio; Claudio, Azzolini; Jaap A., Van
abstract

Recently corneal autofluorescence has been proposed as an ocular diagnostic tool for diabetic retinopathy. The method is based on the sensible increase of the natural fluorescence of corneal tissue within specific wavelength in presence of early stage of diabetic retinopathy. The main advantages of this method are that the corneal autofluorescence has been demonstrated to be not age-related and that the cornea is readily accessible to be investigated. In this study 47 insulin-dependent diabetes mellitus and 51 non-insulin- dependent diabetes mellitus patients aged 20 - 90 years have been considered. Patients were selected from the Eye Clinic of S. Raffaele Hospital. The modified Airlie House classification was used to grade the diabetic retinopathy. Corneal autofluorescence has been measured by using both a specifically designed instrument and the Fluorotron Master. Corneal autofluorescence mean value for each diabetic retinopathy measured by using both the instruments correlated with the retinopathy grade.


1998 - Design and performance of a new fluorometer for corneal autofluorescence measurement [Relazione in Atti di Convegno]
Franco, Docchio; Jaap A., Van; Rovati, Luigi; H. J., Van
abstract

An optical instrument for in-vivo corneal autofluorescence measurements in the human eye is described. This instrument measures corneal autofluorescence without burden to the patient. The corneal tissues are excited tangentially by wavelengths in the spectral region of 450 to 500 nm and the fluorescence emitted by the corneal tissue passing through a suitable set of barrier filters is collected by a miniature photomultiplier. Autofluorescence data are recorded in sixteen measurement cycles during a period of 10 seconds and the average value has been considered. The instrument demonstrates good safety characteristics.


1998 - Diabetic Retinopathy assessed by Dynamic Light Scattering and Corneal Autofluorescence [Articolo su rivista]
Rovati, Luigi; FANKHAUSER F., Ii; Docchio, F.; VAN BEST, J.
abstract

Autofluorescence of the cornea within specific wavelength region and dynamic light scattering measurements of ocular tissue have both been used for early-stage detection of the presence of diabetic retinopathy. In the present study, autofluorescence of the cornea and dynamic light scattering in the cornea and vitreous have been measured and compared using two innovative research instruments in twenty-two insulin-dependent diabetes mellitus patients, for the diagnosis of diabetic retinopathy. Corneal autofluorescence mean values in each diabetic retinopathy grade significantly correlated with dynamic light scattering measurements in the vitreous, and in the cornea, thus confirming that changes in the natural fluorescence is strictly correlated with molecular changes of ocular tissues.


1998 - Low-coherence interferometry using a self-mixing super-luminescent diode [Articolo su rivista]
Rovati, Luigi; F., Docchio
abstract

A novel low-coherence interferometer (LCI) using a self-mixing superluminescent diode is described. The optical scheme proposed uses the photodiode on the back-face of a commercial super luminescent diode to detect the interference signal from a Fizeau interferometer. Interesting characteristics are low cost and small size, high stability and resolution. The proposed interferometer is expected to have several industrial as well as medical applications


1998 - Metrological characterization of a novel absolute distance meter based on dispersive comb-spectrum interferometry [Relazione in Atti di Convegno]
U., Minoni; Rovati, Luigi; M., Bonardi; F., Docchio
abstract

The paper reports results of an investigation on the main measurement uncertainty sources in a novel distance meter based on dispersive comb-spectrum interferometry. The light source is a commercial laser diode operating at 670 nm driven ender the threshold condition, and emitting a beam with a comb-shaped spectrum. Sensitivity of the measurement to the operating conditions has been evaluated. Results from an experimental activity aimed at characterizing the laser and to measure the performance of a prototype implementation are also presented. The system is suitable to perform unambiguous non-incremental distance measurements over a range of 0.8 mm with a total uncertainty of about 1.5 um


1998 - Self-mixing low-coherence interferometry [Relazione in Atti di Convegno]
Rovati, Luigi; Giovanni, Musatti; Franco, Docchio
abstract

In this paper a novel low-coherence interferometer using a self-mixing super luminescent diode is described. The optical scheme presented uses the photodiode on the back- face of a commercial super luminescent diode to detect the interference signal. The low-coherence interferometer, here proposed, for the first time sums up a Fizeau interferometer


1997 - Autofluorescence of ocular tissues: an update of measurement techniques for research and diagnosis [Relazione in Atti di Convegno]
Franco, Docchio; Rovati, Luigi
abstract

Ophthalmic diagnosis through measurements of ocular tissues autofluorescence has recently reached its first clinical maturity. This technique is intrinsically non-invasive and, thanks to the availability of a new family of measuring instruments, is becoming reliable even if performed in a few seconds and is of no burden to the patient. Diagnostic methods based on ocular tissue autofluorescence could become important tools in the prevention of a number of diseases which may lead to blindness, and therefore have a great social impact. The present paper is intended to give, from one side, an update of the rationale concerning fluorophores in the eye and their absorption and fluorescence properties; from the other, it offers an overview of ophthalmic fluorescence techniques aimed at the detection, quantitation and discrimination of ocular autofluorescing substances, highlighting their usefulness as a diagnostic aid in the early detection and prevention of ocular diseases.


1997 - Dispersive white light combined with a frequency-modulated continuous-wave interferometer for high-resolution absolute measurements of distance [Articolo su rivista]
ROVATI, Luigi; U., Minoni; F., Docchio
abstract

A nonincremental interferometer for the absolute measurement of distances is presented. The measuring technique is based on both dispersive white-light (DWL) interferometry and frequency-modulated continuous-wave (FMCW) interferometry. The proposed configuration integrates both techniques in the same interferometer by use of a single laser diode. This solution enables the results from the coarse measurements from the FMCW interferometer to be combined with the fine readouts from the DWL interferometer. Preliminary experimental results confirm the capability of the system to combine the advantages of the two techniques.


1997 - Hollow-beam geometry for dynamic light scattering measurements: a theoretical analysis [Articolo su rivista]
ROVATI, Luigi
abstract

Hollow-beam geometry, in conjunction with mode-selective detection, is of importance for the development of high-sensitivity devices for the measurement of dynamic light scattering in living tissues. Its application to scattering methods in the eye makes it possible to increase diagnostic ability for some diseases that alter the scattering parameters in the vitreous as well as in other transparent tissues of the eye. We present a thorough theoretical analysis of the hollow-beam geometry proposed recently for dynamic light scattering measurements in the human eye. The aims of the analysis are the determination of the excitation and the observation beam profiles at the focal plane and the evaluation of the volume under test in the measurement, which allow prediction of the intensity of the measured signal. The above is carried out with comparisons with the classical setup. From the theoretical point of view, the most appealing feature of the hollow-beam geometry is high collection efficiency combined with high stability. In the analysis performed, the concept of the characteristic length of a scattering system is introduced. With simple formalism, this parameter allows the calculation of the collection efficiency for general beam shaping and is extremely useful for the comparison of the performance of different systems.


1997 - In-vivo measurements of Rayleigh ratio of ocular tissue [Relazione in Atti di Convegno]
Rovati, Luigi; Franz Fankhauser, J. r.
abstract

Recently, we presented a new research instrument to perform dynamic light scattering measurements in each section of the eye axis from the cornea to the retina. Using this instrument, a set of in vivo measurements of static scattered light at the scattering angle of 174 degree(s) on different ocular tissues has been performed. From these measurements the Rayleigh ratio has been evaluated. The motivation for the present study is the complete lack, in literature, of this important scattering parameter for ocular tissue. Rayleigh ratio is important to evaluate a- priori the predetection signal achievable by scattering probes from different ocular tissues. In vivo measurements have been performed on thirty normal subjects aged 16 - 73 years, and Rayleigh ratio has been evaluated as a function of the measuring position and subjects age.


1997 - Theoretical analysis of the hollow beam geometry for dynamic light scattering [Relazione in Atti di Convegno]
Rovati, Luigi
abstract

Hollow beam geometry in conjunction with mode-selective detection allows to realize high-sensitivity apparatuses for quasi back-scattering measurements. I present a complete theoretical analysis of the hollow beam geometry recently proposed for dynamic light scattering measurements in the human eye. The aim of the analysis is to determine the excitation and observation beam profiles at the focal plane, the volume under test and the pre-detection signal. In the analysis the concept of characteristic length of a scattering system is introduced. Using a simple formula, this parameter allows the calculation of the collection efficiency for a general beam shaping. Moreover it is extremely useful to compare the performance of different systems.


1996 - Clinical use of NIR laser reflectometry [Relazione in Atti di Convegno]
Paolo, Lago; Rovati, Luigi; Andrea, Gelmetti; Roberto, Colombo; Ugo, Corra; Francesco De, Vito; P., Giannuzzi; G., Minuco; Mario, Corti
abstract

The potential of optical measurement techniques in the near infrared spectral range becomes increasingly recognized. Continuous wave laser reflectometry is a non-invasive and sensitive method to determine perfusion and oxygenation variations of a specific organ in-vivo. The knowledge of physiological and pathological changes of blood characteristics in body tissues has relevant clinical interest. The improvements of optical and electronic devices offer new possibilities to design reliable and precise instruments to satisfy medical users demand. The results of a collaboration between instrumental designer and physicians are presented. A new method for measuring skeletal muscle oxygenation during exercise and evaluating rehabilitation effects was developed. Two laser diodes generate the wavelengths to select oxygenated and deoxygenated hemoglobin and a fiber optic probe connects the instrument to the patient.


1996 - Design and performance of a new ophthalmic instrument for dynamic light-scattering measurements in the human eye [Articolo su rivista]
Rovati, Luigi; F., Fankhauser II; J., Ricka
abstract

A new optical instrument for in vivo dynamic light-scattering measurements in the human eye isdescribed. The instrument is based on the well-known dynamic light-scattering technique. Resultscan be obtained from the anterior as well as the posterior segment with high spatial resolution andsensitivity. This instrument allows, to our knowledge for the first time, in vivo measurements ofdynamic light scattering to be performed in the vitreous. Interesting performance is obtained usingsingle-mode optical fibers to guide the excitation and the scattered light resulting in a modular,compact system with high-beam quality and electrical insulation of the patient. The instrumentdemonstrates good safety characteristics ~the optical power impinging the patient’s eye is 36 timesbelow the maximum laser power at the cornea, recommended for intrapupil exposure by ANSIstandard!. To demonstrate the possible clinical use of this technique, in vivo measurements weremade and the results compared with the known eye pathologies.


1996 - Dynamic light scattering spectroscopy of in-vivo human vitreous [Relazione in Atti di Convegno]
Rovati, Luigi; Franz Fankhauser, J. r.; Jaro, Ricka
abstract

In-vivo dynamic light scattering measurements in the vitreous of the human eye are presented. The set-up employs single-mode optical fibers for the delivery of the excitation beam and for the collection of the scattered light. High sensitivity and good spatial resolution are achieved using a novel scattering geometry: the excitation beam is shaped into a hollow cone and the scattered light collected through its central part. The apparatus exhibits excellent safety characteristics: the optical power entering the patient's eye is 36 times less than the maximum laser power at the cornea recommended for intrapupil exposure by the ANSI standard. Following a description of the instrument, examples of in-vivo measurements in the vitreous are discussed in order to demonstrate the possible clinical use of this technique.


1996 - Innovative application of semiconductor laser diode [Capitolo/Saggio]
F., Docchio; Rovati, Luigi; U., Minoni
abstract

Innovative application of semiconductor laser diode


1995 - A non invasive instrument for in vivo dynamic laser light scattering measurement in the human eye [Relazione in Atti di Convegno]
Rovati, Luigi; Ii, Fankhauser; J., Ricka
abstract

A new optical instrument for `in vivo' analysis of ocular tissue is presented. The instrument is based on the well know dynamic light scattering technique. Using optimal beam shaping the analysis can be achieved in the cornea and in the anterior chamber as well as in the lens and in the vitreous with high spatial resolution and sensitivity. In order to obtain high beam quality, to provide modularity and galvanic insulation of the instrument, monomode optical fibers are used to guide the excitation and the scattered light. Following a description of the instrument, preliminary `in-vivo' measures are discussed in order to asses the performance of the instrument in ophthalmology diagnostics


1995 - An integrated instrumentation for light-scattering and time-resolved fluorescence measurements [Articolo su rivista]
M., Musolino; R., Cubeddu; A., Pifferi; P., Taroni; P., Lago; Rovati, Luigi; M., Corti
abstract

An integrated instrumentation which combines in the same system static and dynamic laser lightscattering and time-resolved fluorescence spectroscopy is described. The two types of measurementscan be performed simultaneously on the same sample contained in a thermostated cuvette. The lightscattering allows measurements of molecular weights and hydrodynamic radii in the range of 20 8,to a few micrometers. The overall time resolution of fluorescence measurements is around 50 ps.The system provides the simultaneous acquisition of the tluorescence decay curve, of the timeintegrated emission spectrum, and of two time-gated spectra. The light-scattering technique givesinformation on the global structure of the aggregates, while fluorescence measurements are sensitiveto the local interactions of a fluorescence probe with the surroundings. The contemporary use ofthese two complementary techniques can be quite valuable mostly for biological samples for whichstability and reproducibility with time can sometimes be a problem. As an example, combinedmeasurements of the dimension of dimyristoylphosphatidylcholine vesicles around theirtemperature transition and of fluorescence lifetimes of the diphenylhexatriene probe incorporated inthe vesicles is shown.


1995 - Simple NIR instrument for diagnostic purposes [Relazione in Atti di Convegno]
Rovati, Luigi; Paolo, Lago; Roberto, Colombo; Ugo, Corra; Francesco De, Vito; Mario, Corti
abstract

A noninvasive NIR instrument for diagnostic purposes is presented. It is specifically designed for clinical tests during exercise. The instrument makes use of the most modern optical components and a high performance front-end electronics to enhance the signal to noise ratio and to reject stray light effect. A new signal analysis is proposed. The main features are low noise, high stability and readability.


1994 - A multiple-input digital correlator for the weak light scattering signals of chromatographic detectors [Articolo su rivista]
P., Lago; Rovati, Luigi; D., Cuffaro; M., Corti; A., De Agostini
abstract

A simple digital correlator with four independent inputs is described. It gives 20 correlationpoints for each channel, with a maximum sampling frequency of 1 MHz, and is fully computercontrolled. The correlator is designed to match the requirements of dynamic light scatteringdetectors in liquid chromatography.


1994 - A sensitive polarized fluorometer for clinical tests [Articolo su rivista]
P., Lago; Rovati, Luigi; M., Corti
abstract

A fully automated fluorometer which measures fluorescence depolarization is described. The instrument has been designed to work with standard microtiter sample holders normally used in clinical tests. The combination of a hybrid optical system, built with discrete optical elements and fiber bundles, and a digital Fourier analysis of the detected signals make the instrument quite sensitive and precise. The 96 samples are scanned in about 100 s, with a reproducibility of the measurement of the polarization ratio of about 10-3 and a minimum content of fluorescein in the sample well of 20 pmol


1994 - High performance single stage shaper-preamplifier for optical gated signals [Articolo su rivista]
Rovati, Luigi; P., Lago; L., Priori
abstract

A new single stage, low noise, shaper-preamplifier for opticalgated signals is described. Careful layout and accurate componentselection allow the use of CMOS analogue switches before signalamplification without deterioration of the noise performance ofthe preamplifier. With a silicon photodiode, the minimumdetectable signal is less then 3000 photons for a pulse duration of960 us at l = 810nm.


1994 - Noninvasive monitoring of human muscle oxygenation during exercise by near-infrared spectroscopy [Relazione in Atti di Convegno]
R., Colombo; U., Corra; F., De Vito; P., Giannuzzi; P., Lago; Rovati, Luigi; M., Corti; G., Minuco
abstract

Describes an instrument, based on near infrared spectroscopy and measuring the muscle reflectance of the deoxygenated (Hb) and oxygenated (HbO2) components of hemoglobin-myoglobin. The light generated by two laser diodes operating at 750 nm for Hb and at 810 nm for both Hb and HbO2 is transmitted to the tissue. The backscattered light is conveyed to a sensitive photon detector. The instrument is connected to a PC for data collection and storage. The system has been tested in 20 CAD patients performing a bicycle exercise test. A second exercise test was repeated in the same conditions. The measurement reproducibility was evaluated comparing the computed 750/810 parameter in the two trials with: (A) regression analysis for different exercise loads. (B) t test analysis carried out on 12 parameters extracted from the 750/810 waveform; no significant differences were found in any parameter. (C) Intraclass reliability correlation computed on the above defined parameters, which showed excellent scores


1994 - Optoelectronic instrumentation for biological research and the clinical laboratory [Relazione in Atti di Convegno]
Mario, Corti; Paolo, Lago; Rovati, Luigi
abstract

Optoelectronic instrumentation finds increasing applications in the clinical-laboratory work and in biological research. Radioimmunological tests start being substituted by methods which quantify immunoreactions by means of non-hazardous optical techniques. The main ideas involved in the design of such optical instruments, like photometers for enzyme immunoassay or precise fluorometers for fluoroimmunology, are briefly described. Emphasis is then given to a new development in optical detectors for liquid chromatography, that is a very sensitive dynamic-laser-light-scattering system which measures the hydrodynamic radius of the eluting macromolecules directly after the column. Calibrations or knowledge of ancillary parameters, like the refractive-index increment and concentration, are not required.


1994 - Simple noninvasive laser diode oxymeter for measurements on human tissues [Relazione in Atti di Convegno]
Paolo, Lago; Rovati, Luigi; Roberto, Colombo; Ugo, Corra; Francesco De, Vito; Mario, Corti
abstract

A compact, light, easy to use, and low cost instrument with technical solutions that make it suitable for wide clinical use is presented. It is specifically designed for rehabilitation of patients after heart failure. The instrument makes use of low power laser diodes, at 750 and 810 nm, and a remote fiber optic probe. Reflectance change at two wavelengths is used to determine variations of the oxygen content of tissues. A time-variant filter enhances signal to noise ratio and rejects stray light. This specific electronic device allows the use of a low-cost, small and reliable photodiode in place of a photomultiplier tube. Time division techniques is used to process both 750 and 810 signals with a single collecting fiber, photodiode, and preamplifier. The instrument output is two analog signals proportional to the reflectance intensities at 750 and 810 nm, so it is possible to acquire these signals by a PC with a standard A/D board to drive directly a chart recorder. Some clinical tests during the exercise are presented.


1994 - Spatial localization of absorbing zones in a turbid media using NIR CW lasers [Relazione in Atti di Convegno]
Paolo, Lago; Rovati, Luigi; Mario, Musolino; Mario, Corti
abstract

Spatial localization of absorbing zones in a turbid media using NIR CW lasers


1993 - A quasielastic light scattering detector for chromatographic analysis [Articolo su rivista]
P., Lago; Rovati, Luigi; L., Cantu; M., Corti
abstract

Very sensitive laser light scattering equipment has been designed to be used in conjunction withchromatographic column separation. The system is prealigned and fully computer controlled. Itgives the hydrodynamic radius of the eluting particles on line during separation. With a He-Nelaser source, the sensitivity is reached with four optical channels and four correlation functionsof the scattered light measured in parallel with a special correlator.


1993 - Optical interferometer for gas bubble vibration measurements with Angstrom sensitivity [Articolo su rivista]
Rovati, Luigi; Paolo, Lago; Mario, Corti; Carlo, Gomarasca
abstract

An optical interferometer which measures the radial pulsations of gas bubbles in liquids withAngstrom sensitivity is described. The gas-liquid interfaces act as mirrors. The interferometer,intrinsically differential, is insensitive to the overall movement of the bubble and to vibrations ofthe optical components. Examples of the resonance behavior of oxygen bubbles in water aregiven.