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.

Method for modifying spatial resolution in the resolution in the reconstruction of images in digital holography

Abstract: The invention concerns a method Method for the reconstruction of holographic images, the holographic image being detected by an image detection device ( 9 ), the holographic image being transformed in a digitized hologram ( 10 ), the digitized hologram ( 10 ) being comprised of a number V r of elementary pixels, the size of which being equal to the holographic image sampling intervals, and of the V r values ( 51 ) respectively associated to the elementary pixels, the method comprising a first step ( 11,12 ) of processing the digitized hologram array, and a second step ( 13,15,16,17,18 ) of hologram reconstruction in the observation plane starting from the digitized hologram processed in the first step, the method being characterised in that the second step is carried out through discrete Fresnel Transform applied on an array of V e values corresponding to pixels having size equal to that of said elementary pixels, wherein said array of V e values ( 50, 51 ) includes said array of V r values and an integer number p=V e −V r >0 of constant values ( 50 ) equal to OS, said number V e of values being inversely proportional to the desired pixel size to be obtained for the reconstructed image ( 14 ). The invention further concerns the instruments necessary to the execution of the method and the apparatus executing it.

Controlling several image parameters in the digital holographic reconstruction process

Abstract: Recent developments in solid-state image sensors and digital computers have made it possible to directly record holograms by Charge Coupled Device (CCD) camera and numerical reconstruction of the object wave front by computer. Digital holograms recorded with a CCD array are numerically reconstructed in amplitude and phase through calculation of the Fresnel-Kirchhoff integral. Two methods are usually adopted to reconstruct digital holograms called Fresnel Transformation Method (FTM) and the Convolution Method (CM). In FTM, the reconstruction pixel increases with the reconstruction distance so that the size of image, in terms of number of pixels, is reduced for longer distances, limiting the resolution of amplitude and phase reconstruction. In CM, by contrast, the reconstruction pixel does not change, but remains equal to the pixel size of recording array. The CM is more appropriate for reconstruction at small distances whereas the FTM is useful for longer distances according to the paraxial approximation necessary to apply it. The flexibility offered by the reconstruction process in Digital Holography allows exploitation of new possibilities of application in different fields. Through the reconstruction process we will show that it is possible to control image parameters as focus distance, image size and image resolution. Those newly explored potentialities open further novel prospective of application of Digital Holography in single and multi-wavelengths operation either for display and metrological applications. We demonstrate the concept of controlling parameters in image reconstruction of digital holograms in some real situations for inspecting silicon MEMS structures.

Manipulating Thin Liquid Films for Tunable Microlens Arrays

Abstract: Nano-optics: The coupling of micro-fluidics and array imaging opens a fascinating area of research.

Lock-in Thermography as a tool for the Detection of Damages in “Eco” Composite Materials

Abstract: Thanks to their advanced properties, composite materials have found applications in important industrial sectors. In particular, in the last decades, the use of natural reinforcing fibers has gained an increasing attention allowing the development of new materials with the same advantages of conventional composite systems but respecting the environment, too. In this frame, the development and identification of fast and low cost non-destructive tools for their quality control is of fundamental importance. In this work, the Lock-in thermography was tested for the analysis of samples belonging to six different "eco" composite materials on which delamination damage was induced. The results obtained are promising and show how the active thermography technique used is well suited for the detection of this kind of defects allowing also a quantitative characterization of their extension.

Finding intracellular lipid droplets from the single-cell biolens' signature in a holographic flow-cytometry assay.

Abstract: In recent years, intracellular LDs have been discovered to play an important role in several pathologies. Therefore, detection of LDs would provide an in-demand diagnostic tool if coupled with flow-cytometry to give significant statistical analysis and especially if the diagnosis is made in full non-invasive mode. Here we combine the experimental results of in-flow tomographic phase microscopy with a suited numerical simulation to demonstrate that intracellular LDs can be easily detected through a label-free approach based on the direct analysis of the 2D quantitative phase maps recorded by a holographic flow cytometer. In fact, we demonstrate that the presence of LDs affects the optical focusing lensing features of the embracing cell, which can be considered a biological lens. The research was conducted on white blood cells (i.e., lymphocytes and monocytes) and ovarian cancer cells. Results show that the biolens properties of cells can be a rapid biomarker that aids in boosting the diagnosis of LDs-related pathologies by means of the holographic flow-cytometry assay for fast, non-destructive, and high-throughput screening of statistically significant number of cells.

Fourier-transform method of fringe-pattern analysis for computer-based topography and interferometry

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.

Fiber grating sensors

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.