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ETTORE MASETTI
Dottorando
Dipartimento di Ingegneria "Enzo Ferrari"
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Pubblicazioni
2023
- A transimpedance preamplifier using a feedforward approach for robust rejection of DC photogenerated currents
[Articolo su rivista]
Masetti, E.; Cattini, S.; Rovati, L.
abstract
The preamplifier proposed in this paper is designed to extract weak variable photogenerated signals from a high-level continuous background ensuring low noise and high transimpedance gain. An efficient cancellation of the DC component directly at the photodetector output, exploiting a feedforward approach, allows us to properly amplify the variable signal components of interest avoiding saturation of the preamplifier. Furthermore, the large transimpedance gain allows for minimizing the effects of the noise introduced by the following stages on the signal processing chain. In the paper, we present the proposed approach and a possible circuit realization with a signal AC/DC ratio as small as 1/1000 ensuring low noise, high gain, and a considerable bandwidth. The realized preamplifier offers a Noise Equivalent Power NEP ≃ 1.12 nW, an in-band transimpedance gain of 4.4 MΩ, and a wide bandwidth from about 1 Hz up to 100 kHz, making it suitable for use in several applications both in biomedical and industrial fields.
2023
- Laplacian-Based Focus Measure Allows Rapid Focus Estimation of Annular Regions in Gray-Scale Images
[Relazione in Atti di Convegno]
Masetti, E; Giardini, Me; Ruggeri, M; Rovati, L
abstract
Important ophthalmic imaging techniques, such as fundus camera imaging, utilize light sources that need to be focused on an annular section of an eye surface. In order to be performed dynamically, this requires real-time control of the focus plane of the illumination optics. When considering adaptive focusing in ophthalmic instruments, liquid lenses represent the best compromise in terms of tunability, tuning range, compactness, numerical aperture, and speed. In recent years, several compact eye imaging devices using liquid lenses have been described in the literature. These would benefit from low computational complexity algorithms for adaptive local auto-focus on an annular region, to allow the illumination optics to be controlled by low-cost and low-power electronics. In this paper, we propose a novel radial-focus evaluation method based on a revised version of a more traditional Laplacian-based focus estimator. This radial focus evaluation is targeted to focusing annular sections of an image, with the advantage of a drastic reduction of computational complexity.
2023
- On the use of a liquid lens for improving iris images quality in a hyperspectral system
[Relazione in Atti di Convegno]
Masetti, Ettore; Rovati, Luigi
abstract
In this paper, we describe how using a liquid lens can improve the quality of iris images acquired by a hyperspectral system. This improvement in the image quality is especially noticeable for systems that scan the iris over a wide range of wavelengths, e.g. visible and near-infrared spectrum. We have tested this approach on the previously developed system able to acquire iris images in the spectral range 480 - 900 nm. The key novelty presented in this paper is represented by the possibility of adaptively adjusting the focus of the imaging system, allowing for chromatic aberration compensation and ensuring a constant image sharpness among all wavelengths. A fast-tunable liquid lens has been placed in front of the chromatically corrected camera objective to adaptively change the overall focus of the imaging system. The findings imply that the device can rapidly perform hyperspectral measurements of the iris over a broad wavelength range ensuring optimal focus for all images.
2022
- Absolute distance measurements based on TD SM-SLD: performances characterization and calibration
[Relazione in Atti di Convegno]
Masetti, Ettore; Fedullo, Tommaso; Cattini, Stefano; Rovati, Luigi
abstract
Time-Domain Low-Coherence Interferometry (TD-LCI) is a well-known optical method to perform absolute distance measurements. As an alternative to conventional TD-LCI, the Self-Mixing Super Luminescent Diode (SM-SLD) technique represents a unique approach for simplicity and compactness. The presence of optical feedback in the source cavity allows obtaining huge interference fringes, even with diffusive targets and without using high-sensitivity and low-noise detectors. In this work, we present the performances of a custom-made SM-SLD interferometer for absolute distance measurements compared with a reference incremental interferometer. Thanks to the simplified acquisition method and the resulting improved signal-to-noise ratio, the system exhibits excellent metrological performances.
2022
- On the Use of an Hyperspectral Imaging Vision Based Measurement System and Machine Learning for Iris Pigmentation Grading
[Relazione in Atti di Convegno]
Fedullo, T.; Masetti, E.; Gibertoni, G.; Tramarin, F.; Rovati, L.
abstract
Nowadays, the ability to derive accurate measurements from images, i.e. the application of vision-based systems to the measurement field, is becoming an attractive research field. In this context, Machine Learning (ML) algorithms can be exploited to smartly and automatically perform the measurement activity. This paper presents an interesting application of ML techniques to an Hyperspectral Imaging System, devoted to the analysis of the iris pigmentation. Indeed, it is proven that the iris pattern evaluation gives a chance for the analysis of both possible loss of sight and future outbreak of several eye diseases. The proposed Vision-Based Measurement system (VBM) allows to illuminate the subject eyes in the spectral range 480 - 900 nm. In particular, the imaging system foresees to take 22 different images of 2048 x 1536 pixels, thus obtaining a spectral resolution of 20 nm and a spatial resolution of 10.7 μm. In this paper, as a first research step, we evaluate the possibility to develop a suitable Machine Learning algorithm to classify the iris color. In particular, the goal is to point out the possible ML techniques that can be employed, the needed dataset and the possible advantages offered by the hyperspectral approach, compared to the conventional visible light imaging.
2021
- A Technique for Improving the Noise-Equivalent-Displacement of SM-SLD Interferometers for Industrial Processes
[Relazione in Atti di Convegno]
Masetti, Ettore; Rovati, Luigi; Cattini, Stefano
abstract
Non-contact absolute distance measurements are desirable in several industrial processes. For this purpose, the interferometric Self-Mixing Super Luminescent Diode technique represents a unique approach for simplicity and robustness. Thanks to optical feedback, large interference fringes, even with diffusive targets and without utilizing high-sensitivity detectors, can be obtained rejecting any stray-light. To establish the absolute target position, the most common approach is to process the interference fringes envelope by the zero-crossing technique. In this paper, we propose to process the photogenerated signal by a custom modified envelope detector to reduce the measurement uncertainty.
2021
- Combined anterior segment OCT and wavefront-based autorefractor using a shared beam
[Articolo su rivista]
Ruggeri, Marco; Belloni, Giulia; Chang, Yu-Cherng; Durkee, Heather; Masetti, Ettore; Cabot, Florence; Yoo, Sonia H.; Ho, Arthur; Parel, Jean-Marie; Manns, Fabrice
abstract