Showing papers by "Pietro Ferraro published in 1998"
ARCO1
TL;DR: In this article, a technique based on two-dimensional fast Fourier fringe analysis for the automated evaluation of the inclination angle of parallel fringe patterns is described and numerical results of the angle evaluation error using this algorithm are discussed.
Abstract: In this paper we describe a technique based on two-dimensional fast Fourier fringe pattern analysis for the automated evaluation of the inclination angle of parallel fringe patterns. Analysis of noise-free theoretical parallel fringe patterns is presented and numerical results of the angle evaluation error using this algorithm are discussed. We also demonstrate an application of the method to the measurement of the inclination angle of experimental parallel fringe patterns.
24 citations
ARCO1
TL;DR: In this article, a non-iterative Fourier transform method for phase retrieval of a carrier-modulated fringe pattern is described, in which the phase information is extracted by using a single operation to remove the linear carrier and to calibrate the final result without the intermediate calculation of the carrier phase function and without shifting in frequency domain the filtered Fourier spectrum.
15 citations
ARCO1
TL;DR: In this article, the authors describe a technique based on fast Fourier transform and least squares fit for automated analysis of moire fringe patterns for accurately measuring the focal length of lenses, and they show that in the latter case by means of the described technique it is possible to determine the moire spatial frequency by a simple and fully automated procedure.
14 citations
ARCO1
TL;DR: In this paper, a method based on an interferometric technique to measure the molecular distortion induced by an incident light beam on a nematic liquid crystal film was proposed and an analysis of the fringe pattern generated by means of a Fourier transform method allowed comparison of the measurements with the theoretical molecular distribution.
Abstract: We propose a method based on an interferometric technique to measure the molecular distortion induced by an incident light beam on a nematic liquid crystal film. An analysis of the fringe pattern generated by means of a Fourier transform method allows comparison of the measurements with the theoretical molecular distribution. From this analysis an estimation of the elastic anisotropy of the liquid crystal is derived which is in good agreement with previous results.
6 citations
TL;DR: When an object is partially immersed and inclined in the water, the shadow of the object seen on the bottom of the container appears to be broken in two distinct parts or blown up in correspondence of the immersion line.
Abstract: When an object is partially immersed and inclined in the water, the shadow of the object seen on the bottom of the container appears to be broken in two distinct parts or blown up in correspondence of the immersion line. The effect is very simple to show and observations and discussions could be developed in the classroom about surface tensions, wettability, and optics.
5 citations
ARCO1
TL;DR: In this article, an interferometric technique based on high precision two-dimensional spatial fringe analysis Fourier method for measuring the elastic constants of nematic liquid crystals was proposed, where the determination of the elastic anisotropy relies on the measurement of the ratios between the elastic coefficients.
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.
2 citations