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.

Improvement of the reconstruction algorithm for extended focus image of MEMS by digital holography

Abstract: Digital Holographic Microscopy (DHM) is an optical interferometric technique for not destructive testing of micro-electro-mechanical systems (MEMS). A characterization process based on a no-contact technique allows us to analyze deformations, warping, residual stress, cracks and more other defects of MEMS, without destroy them. The flexibility of this technique allows us to improve novel numerical reconstruction algorithm for the recovery of more information. The post processing of the acquired holograms allows to reduce noise, optical aberrations, defocusing. In particular, the hologram reconstruction process has been modified to obtain Extended Focus Images (EFI). In Digital holographic microscopy, the use of microscopy objectives with high magnifications, reduces the focus depth. This means that for extended object a single reconstructed image with all the details in focus is not possible to obtain. Using a multiple reconstruction process and opportune resizing algorithms a full focused reconstructed images of extended object has been obtained without any mechanical movement. In particular, the advantages of the EFI technique are unique for dynamical characterization by DHM of extended objects, where the techniques based on multiple acquisitions fail. The EFI technique has been applied to obtain a best focused reconstructed image and profile of some micromechanical systems. It is demonstrated that this new approach allows to improve the accuracy in the EFI image when compared to the previous experimental results. Focusing of zones at different quote has been obtained evidencing, shape, crack and deformation impossible to observe otherwise at the same time. Moreover, these technique of reconstruction and analysis can be advantageous in many other fields of application.

Heterodyne interferometric characterization of polarizing optical devices

Abstract: A heterodyne detection interferometer is described that can be efficiently used to control the state of polarization (SOP) and the phaseshift induced by polarizing optical devices. The basic equations are derived. The technique is used to measure the SOP of linear retarders.

Liquid refractometer based on fringe projection technique

Abstract: Measurement of the refractive index of liquids is of great importance in applications such as characterization and control of adulteration of liquid commonly used and in pollution monitoring We present and discuss a fringe projection technique for measuring the index of refraction of transparent liquid materials© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering Downloading of the abstract is permitted for personal use only

Sensitometric and holographic data of Kodak 120-02 and llford He-Ne 1 plates

Abstract: The macroscopic transfer characteristics of Kodak 120-02 and llford He-Ne/1 plates exposed to diffused laser light at 633 nm and processed in different developers for various times are reported. Diffraction efficiency and signal-to-noise ratio of amplitude holograms recorded in these materials have been checked and compared with the results obtained from other holographic emulsions.

Electrooptic beam deflection with latex

Abstract: The use of latex in electrooptic devices is proposed. The static non linearity coefficient is shown to be approximatively 200 times the optical one. The theory of a beam deflector is developed and an explicit expression is given for the deflection angle versus the physical parameters of the sample Utilisation de suspensions aqueuses de latex dans un dispositif electro-optique. On montre que le coefficient statique de non-linearite devrait etre 200 fois plus eleve que le coefficient optique. Application a un deflecteur optique

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.