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.

Synthesis and 3D display of multi-wavelengths digital holograms through adaptive transformation

Abstract: We propose a reconstructing method of digital color holograms based on the stretching techniques. With a simple affine transformation on the Fresnel reconstructions, we are able to manage the focus of the digital color reconstructions of the same object in order to obtain a synthetic single digital hologram in which three different colors are multiplexed. In addition, a 3D scene is synthesized combining multiple optically recorded digital color holograms of different objects. Numerical analysis and display tests are used to evaluate the effectiveness of the proposed method.

Point-diffraction interferometer by electro-optic effect in lithium niobate crystals

Abstract: We propose a new point-diffraction interferometer (PDI) based on a pinhole filter made by a z-cut lithium niobate (LN) crystal. A thin aluminium layer with a circular opening is fabricated on the surface of the crystal by conventional photolithography and subsequent aluminium deposition and lift-off. This aluminium layer acts both as electrode and as pinhole filter on the exit face of the crystal, while a uniform planar aluminium layer is deposited on the opposite face. When a voltage is applied across the z-axis of the crystal, the refractive index changes everywhere in the crystal except in a small portion underneath the area of the pinhole. Therefore, the applied voltage causes an uniform phase shift over the aberrated wavefront while leaving unaffected the diffracted reference beam passing through the pinhole. The interference taking place behind the sample produces an interference fringe pattern containing the information on the aberrated wavefront. Four phase shifted images of the fringe pattern are acquired and processed by means of the Carre algorithm to retrieve the aberrated wavefront. The proposed PDI arrangement has several important advantages over the other PDI configurations. The technological processes are very simple, and the phase-shift operation can be applied at very high speed limited only by the minimum acquisition time of the camera device. In fact, the electro-optic effect can be induced onto LN with bandwidths up to several GHz. Moreover, LN is transparent in very wide spectral range from 400 nm to 5500 nm, thus being useful in numerous applications.

Probing micro-plastic items with coherent light enables their identification through digital holography

Abstract: Detection of micro-plastics in water samples is a highly pursued goal to map the distribution and abundance of these pollutants. Here we investigate the possibility to probe micro-plastics with coherent light and to image them by digital holography microscopy. From the recorded hologram, we access the phase-contrast map of the object. We show that this map can be used as a distinctive fingerprint to identify microplastics in water.

A simple bi-polished silicon sample to detect vibrations by Fiber Bragg sensor

Abstract: Describes a simple method for interrogating fiber Bragg grating sensors by a bi-polished silicon sample acting like a Fabry-Perot filter. Thus, Bragg wavelength shift is converted into a variation of the light intensity.

A New Interferometric Technique for the Measurement of Elastic Anisotropy of Nematic Liquid Crystals

Abstract: It is well known that a continuous wave laser beam impinging on a nematic liquid crystals film can induce a change in the orientation of the molecular director. In the case of homeotropic alignment and for a p-polarized obliquely incident beam, the reorientation process has no threshold and the sample exhibits a giant optical nonlinearity due to the laser-induced change in refractive index of the medium. In the small distortion approximation the phase change is governed by a linear differential equation whose coefficients depend on the ratio between the elastic constants. In this paper we describe an interferometric technique based on high precision two-dimensional spatial fringe analysis Fourier method for measuring the elastic constants of nematic liquid crystals. Since the determination of the elastic anisotropy relies on the measurement of the ratios between the elastic constants, this technique provides a powerful and high accuracy method for characterizing nematic liquid crystals.

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.