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.

Label free imaging of cell-substrate contacts by holographic total internal reflection microscopy.

Abstract: The study of cell adhesion contacts is pivotal to understand cell mechanics and interaction at substrates or chemical and physical stimuli. We designed and built a HoloTIR microscope for label-free quantitative phase imaging of total internal reflection. Here we show for the first time that HoloTIR is a good choice for label-free study of focal contacts and of cell/substrate interaction as its sensitivity is enhanced in comparison with standard TIR microscopy. Finally, the simplicity of implementation and relative low cost, due to the requirement of less optical components, make HoloTIR a reasonable alternative, or even an addition, to TIRF microscopy for mapping cell/substratum topography. As a proof of concept, we studied the formation of focal contacts of fibroblasts on three substrates with different levels of affinity for cell adhesion.

A reflective grating interferometer for measuring the refractive index of liquids

Abstract: A simple and compact interferometric system, which makes use of a reflective-type diffraction grating, has been developed for measuring the refractive index of liquids. This paper describes the details of the system, which is easy to align and compact, and a series of measurements performed on liquids. An analysis of the accuracy of the method is presented, which is proven to be within one part in .

A Nondestructive Dynamic Characterization of a Microheater Through Digital Holographic Microscopy

Abstract: This paper describes the possibility of employing a digital holographic microscope (DHM) to carry out a noncontact and nondestructive characterization of a microheater integrated on a silicon nitride membrane and subjected to a high thermal load. Microheaters can be affected by the presence of the residual stress due to the technological processes appearing in the form of undesired bowing of the membrane. Moreover, when the temperature of the microheater increases, a further warpage of the structure can be induced. A DHM allows for evaluation, with high accuracy, the deformations due to the residual stress and how these deformations are affected by the thermal loads due to the microheater operating mode. In particular, this dynamic analysis is made possible by measuring the unwanted longitudinal displacement induced by the thermal expansion of both the device and its mechanical support. Taking into account this displacement, it is possible to have a continuous monitoring of profile deformation induced by the working condition of the microheater.

Compression of digital holograms via adaptive-sparse representation

Abstract: Efficient storage and transmission of digital holograms (DHs) requires the development of appropriate compression techniques for such a special class of images. In this Letter, we investigate a method to compress DHs using a sparse matrix representation. Using digital holography to numerically manage complex wave fields, we are able to apply an adaptive mask, based on a threshold filter, to the object wave field. From there, we store the result of this filtering by sparse representation. In this Letter, we demonstrate that using sparse representation allows for a high compression factor with minimal loss in the quality of the reconstructed image. This technique is efficient for storage and transmission of DHs.

Mid-infrared tunable two-dimensional Talbot array illuminator

Abstract: We report the realization and characterization of a tunable, two-dimensional Talbot array illuminator for mid-infrared (MIR) wavelengths. A phase array, prepared by deposing tin-doped indium oxide electrodes on a square-lattice-geometry poled LiNbO3 sample, is illuminated by a difference-frequency generator emitting at 3 μm. Then, combining the electro-optic with the Talbot effect allows generation of a variety of light patterns under different values of distance and external electric field. Several potential applications with great relevance to the MIR spectral region are discussed.

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.