Showing papers by "José A. Ferrari published in 1998"
TL;DR: In this article, a phase step interferometry system using polarization shifting is described, which is essentially a Mach-Zehnder interferometer in which the polarization of light travelling through one arm is orthogonal to the polarization travelling through the other arm.
Abstract: A phase step interferometry system using polarization shifting is described. The device is essentially a Mach-Zehnder interferometer in which the polarization of light travelling through one arm is orthogonal to the polarization of light travelling through the other arm. At the interferometer output we place a quarter-wave plate with its fast axis at with respect to the polarization directions and a polarizer. By rotating the polarizer, the interfering waves acquire an extra phase (of topological origin) to that expected from the calculations of optical path lengths, and thus, arbitrary phase shifts can be induced. Then, from a set of interferograms recorded while the reference phase is changed, the `dynamical' phase difference (e.g. the phase profile of an object placed in one of the interferometer arms) can be reconstructed by using techniques of phase-shifting interferometry.
20 citations
TL;DR: In this paper, a nonlinear joint transform correlator (NJTC) was proposed for processing the data in a bidimensional image and the output of the NTC was obtained after two steps.
Abstract: We present a new method for processing the data in a nonlinear joint transform correlator (NJTC). The output of the NJTC is obtained after two steps. The first step consists of the acquisition of the joint power spectrum (JPS) of the images to be correlated. The JPS is in principle a bidimensional image. The second step is the calculation of the cross-correlation function. To do this, the JPS image is compressed to one dimension and a 1-D Fourier transform is performed. This significantly reduces the number of operations required to evaluate the crosscorrelation. To improve the cross-correlation sensitivity, a degree of nonlinearity is introduced using an illumination level above the saturation threshold of the camera used to acquire the JPS.
4 citations
TL;DR: In this article, the authors show how to correct polarization measurements performed with non-ideal polarizers, which can be used to perform precise polarization measurements using inexpensive polarizing sheets, but they do not specify the type of sheet used.
Abstract: We show how to correct polarization measurements performed with non-ideal polarizers. The formulas presented in this note can be used to perform precise polarization measurements using inexpensive polarizing sheets.
3 citations
TL;DR: In this article, a method to determine the complex coherence function is proposed based on the concept of geometric phase, which has the property of achromaticity, which enables adding phase delays to the entire interferogram.
3 citations
TL;DR: In this paper, the reflected laser beam becomes phase modulated by the acoustic wave as in acoustical holographic systems, which gives a measurement of the acoustic field power as a function of the position.