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Pietro Ferraro

Bio: Pietro Ferraro is an academic researcher from National Research Council. The author has contributed to research in topics: Digital holography & Holography. The author has an hindex of 61, co-authored 653 publications receiving 12666 citations. Previous affiliations of Pietro Ferraro include Aeritalia & Centre national de la recherche scientifique.


Papers
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Proceedings ArticleDOI
28 Apr 2006
TL;DR: In this article, the optical phase difference (OPD) between the light beam traveling through the layer and portion of the beam in air is measured exploiting an interferometric technique, which can be used even for inspection of nonplanar or stressed structures.
Abstract: In this paper is reported a method for measuring the thickness of a silicone nitride layers employed for fabricating silicon MEMS bi-morph structures. The method allows the precise evaluation of layer thickness by adopting Digital Holographic Microscope. The measurement is based on the fact that the silicon nitride layer is transparent to the visible light. The optical phase difference (OPD) between the light beam traveling through the layer and portion of the beam in air is measured exploiting an interferometric technique. The approach is very simple and can be utilized even for inspection of non-planar or stressed structures. Experimental values have been compared with ellipsometric measurements.

1 citations

Proceedings ArticleDOI
01 Mar 2019
TL;DR: The joint action of numerical ML (thought as a preprocessing filter) and 3D Block Matching in post-processing permits to overcome the theoretical limit of ML and to outperform the BM3D for the denoising of holograms.
Abstract: Digital Holography (DH) suffers from severe degradation of the reconstruction quality due to the presence of speckles. Speckle is due to the source coherence and shows on the hologram as a multiplicative, correlated noise. Due to the larger size of the speckle grains, the lower resolution, and the worse features of the available hardware, long wavelength digital holography is more severely degraded by noise than its visible wavelength counterpart is. Non-Bayesian approaches to the denoising problem suffer from resolution loss or complex acquisition systems required to record multiple uncorrelated holograms to be averaged. Instead of providing multiple captures, these can be simulated to yield a number of reconstructions from one single hologram (generally referred to as numerical Multi-Look, ML). However, the ML improvement is inherently bounded to a theoretical limit. On the other hand, image processing has offered a wide literature on the topic over the last decades. Among the most efficient methods to reduce additive Gaussian noise, 3D Block Matching (BM3D) has emerged and it is nowadays widely used in the image processing framework. However, BM3D performance worsens in the presence of speckle and cannot be effectively applied to long wavelength DH. Here we show that the joint action of numerical ML (thought as a preprocessing filter) and BM3D in post-processing permits to overcome the theoretical limit of ML and to outperform the BM3D for the denoising of holograms. The quasi noise free reconstruction of long wavelength holograms of famous artworks will be shown.

1 citations

Proceedings ArticleDOI
TL;DR: In this paper, a single linear sensor array is sufficient to create hybrid interferograms with unlimited Field of View (FoV) along the scanning direction, and allowing quantitative phase retrieval by Phase Shifting (PS) interferometry algorithms.
Abstract: Here we show a novel imaging modality, named Space-Time Scanning Interferometry (STSI), which synthesizes interferograms mapped in a hybrid space-time domain. A single linear sensor array is sufficient to create hybrid interferograms with unlimited Field of View (FoV) along the scanning direction, and allowing quantitative phase retrieval by Phase Shifting (PS) interferometry algorithms. We applied the STSI method to microfluidic imaging of biological samples, where the required phase shift between interferograms is intrinsically offered due to the sample movement. Besides, out-of-focus recordings are performed using a single line detector, in order to synthesize an unlimited FoV Space-Time Digital Hologram (STDH) yielding full-field, 3D information. Experimental proofs have been carried out to demonstrate the useful capability of STDH to overcome the trade-off existing between FoV and sample magnification, thus providing a high-throughput, label/free, quantitative, diagnostic tool to study biological elements onboard LoC platforms.

1 citations

Proceedings ArticleDOI
24 Jun 2019
TL;DR: The possibility to merge different denoising strategies, by considering optical and numerical methods, permits to sensitively reduce the speckle noise in digital holography.
Abstract: The possibility to merge different denoising strategies, by considering optical and numerical methods, permits to sensitively reduce the speckle noise in digital holography. Some examples are made to quantify the performance of these hybrid methods.

1 citations


Cited by
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Journal Article
TL;DR: In this article, a fast Fourier transform method of topography and interferometry is proposed to discriminate between elevation and depression of the object or wave-front form, which has not been possible by the fringe-contour generation techniques.
Abstract: A fast-Fourier-transform method of topography and interferometry is proposed. By computer processing of a noncontour type of fringe pattern, automatic discrimination is achieved between elevation and depression of the object or wave-front form, which has not been possible by the fringe-contour-generation techniques. The method has advantages over moire topography and conventional fringe-contour interferometry in both accuracy and sensitivity. Unlike fringe-scanning techniques, the method is easy to apply because it uses no moving components.

3,742 citations

Journal ArticleDOI
TL;DR: In this paper, the authors review the recent developments in the area of optical fiber grating sensors, including quasi-distributed strain sensing using Bragg gratings, systems based on chirped gratings and intragrating sensing concepts.
Abstract: We review the recent developments in the area of optical fiber grating sensors, including quasi-distributed strain sensing using Bragg gratings, systems based on chirped gratings, intragrating sensing concepts, long period-based grating sensors, fiber grating laser-based systems, and interferometric sensor systems based on grating reflectors.

3,665 citations

01 Jan 2006

3,012 citations