Giovanni Pierattini

Bio: Giovanni Pierattini is an academic researcher from ARCO. The author has contributed to research in topics: Digital holography & Holography. The author has an hindex of 25, co-authored 128 publications receiving 3222 citations. Previous affiliations of Giovanni Pierattini include Olivetti.

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

Abstract: The invention concerns a method for the reconstruction of holographic images in digital holography, the holographic images being detected and transformed in a digitized hologram by an image detection device, the digitized hologram being made of an array having a number Vr of elementary pixels, the sizes of which being equal to the sampling intervals of the image detection device, the method comprising a first step of processing the digitized hologram array (e.g. zero-order elimination, aberration correction), and a second step of digitally reconstructing the complex object in an 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 Ve pixels having sizes equal to that of said elementary pixels, wherein said array of Ve pixels (50, 51) includes said Vr pixels (51) and an interger number p=Ve-Vr>0 constant values (50). The invention further concerns the instruments necessary to the execution of the method and the apparatus executing it.

Two-beam shearing interferometric method for testing a conical lens

Abstract: We present a novel interferometric method for testing refractive conical lenses. The optical configuration requires only two mutually coherent plane wave fronts transmitted through the optical component under test. It can be interpreted as reversal shear interferometric technique. The method can also be considered as an interferometric fringe projection method. Measurements have been realized for determining the base angle of the refractive cone under test and the aberrations introduced.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Interferometric measurement of thermo-optic coefficients of transparent materials

Abstract: We describe an interferometric technique based on temperature dependent optical path length changes in thin slab of transparent materials, suitable for measuring the thermo-optic coefficients of transparent materials. This technique allows an accurate determination of the fringe shift corresponding to a change in the sample temperature, by means of a two fringe pattern Fourier-transform based processing algorithm for phase retrieval. The principle of measurement of the method and its applications to the measurements of the thermo-optic coefficients of some commercial glasses are presented and discussed.

Digital holographic microscope for thermal characterization of silicon microhotplates for gas sensor

Abstract: Digital Holographic Microscope has been employed to obtain an accurate characterization of a micro-hotplate for gas sensing applications. The fabrication of these sensors needs different materials, with different properties and different technological processes, which involve high temperature treatments. Consequently, the structure is affected by the presence of residual stresses, appearing in form of undesired bowing of the membrane. Moreover, when the temperature of the sensor increases, a further warpage of the structure is observed. DHM allows to evaluate, with high accuracy, deformations due to the residual stress and how these deformations are affected by thermal loads. In particular, profiles of the structure have been evaluated both in quasi-static condition and the profile variation due to the biasing of the heater resistor has been measured.

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.

Femtosecond laser micromachining in transparent materials

Abstract: Femtosecond laser micromachining can be used either to remove materials or to change a material's properties, and can be applied to both absorptive and transparent substances. Over the past decade, this technique has been used in a broad range of applications, from waveguide fabrication to cell ablation. This review describes the physical mechanisms and the main experimental parameters involved in the femtosecond laser micromachining of transparent materials, and important emerging applications of the technology. Interactions between laser and matter are fascinating and have found a wide range of applications. This article gives an overview of the fundamental physical mechanisms in the processing of transparent materials using ultrafast lasers, as well as important emerging applications of the technology.

Digital recording and numerical reconstruction of holograms

Abstract: This article describes the principles and major applications of digital recording and numerical reconstruction of holograms (digital holography). Digital holography became feasible since charged coupled devices (CCDs) with suitable numbers and sizes of pixels and computers with sufficient speed became available. The Fresnel or Fourier holograms are recorded directly by the CCD and stored digitally. No film material involving wet-chemical or other processing is necessary. The reconstruction of the wavefield, which is done optically by illumination of a hologram, is performed by numerical methods. The numerical reconstruction process is based on the Fresnel–Kirchhoff integral, which describes the diffraction of the reconstructing wave at the micro-structure of the hologram. In the numerical reconstruction process not only the intensity, but also the phase distribution of the stored wavefield can be computed from the digital hologram. This offers new possibilities for a variety of applications. Digital holography is applied to measure shape and surface deformation of opaque bodies and refractive index fields within transparent media. Further applications are imaging and microscopy, where it is advantageous to refocus the area under investigation by numerical methods.

Principles and techniques of digital holographic microscopy

Abstract: Digital holography is an emerging field of new paradigm in general imaging applications. We present a review of a subset of the research and development activities in digital holography, with emphasis on microscopy techniques and applications. First, the basic results from the general theory of holography, based on the scalar diffraction theory, are summarized, and a general description of the digital holographic microscopy process is given, including quantitative phase microscopy. Several numerical diffraction methods are described and compared, and a number of representative configurations used in digital holography are described, including off-axis Fresnel, Fourier, image plane, in-line, Gabor, and phase-shifting digital holographies. Then we survey numerical techniques that give rise to unique capabilities of digital holography, including suppression of dc and twin image terms, pixel resolution control, optical phase unwrapping, aberration compensation, and others. A survey is also given of representative application areas, including biomedical microscopy, particle field holography, micrometrology, and holographic tomography, as well as some of the special techniques, such as holography of total internal reflection, optical scanning holography, digital interference holography, and heterodyne holography. The review is intended for students and new researchers interested in developing new techniques and exploring new applications of digital holography.