Showing papers by "José A. Ferrari published in 2019"
TL;DR: The purpose of the present work is to study the phase extraction from phase-shifted interferograms with arbitrary steps and random phase-noise, and to deduce an algorithm that minimizes the phase-retrieval error induced by weak phase- noise.
8 citations
TL;DR: The aim of the present work is to study the dependence of the light-induced optical density, i.e., the color-center concentration, as a function of the distance traveled inside a photochromic glass body in stationary state, and proposes an experimental setup that allows the direct observation of that concentration from a transversal view.
Abstract: The aim of the present work is to study the dependence of the light-induced optical density, i.e., the color-center concentration, as a function of the distance traveled inside a photochromic glass body in stationary state. We propose an experimental setup that allows the direct observation of that concentration from a transversal view. In particular, we will see that for activating intensities much higher than certain threshold, the photochromic material saturates between the surface and an inflection point that happens at a constant normalized concentration of 2/3. The width of this region depends logarithmically on the activating light intensity. This fact will allow us to determine one of the photochemical constants of the material. Validation experiments are presented.
3 citations
TL;DR: In this paper, the authors proposed a method for orientation-selective enhancement of the first derivatives of a pure phase object based on the transport-of-intensity equation (TIE), which contains a term proportional to the scalar product of the phase gradient and an intensity gradient, which plays the role of amplifying factor of first derivatives.
2 citations
09 Sep 2019
TL;DR: A dual-sensitivity profilometry technique is presented, which is based on defocused projection of binary and sinusoidal fringe patterns with a high and low-frequency spatial carrier, respectively, to reduce the data acquisition time and maintain the quality of the unwrapped phase.
Abstract: In fringe projection profilometry, temporal phase unwrapping is an essential procedure to recover an unambiguous absolute phase even in the presence of large discontinuities or spatially isolated surfaces. In this work, a dual-sensitivity profilometry technique is presented, which is based on defocused projection of binary and sinusoidal fringe patterns with a high and low-frequency spatial carrier, respectively. The binary defocusing techniques (based on PWM or square-wave profile patterns, whose pitch is relatively narrow) have demonstrated successful for high-quality three-dimensional shape measurement when the projector presents a nonlinear response. But they suffer if pitch fringe is wide. On the other hand, using dual sensitivity profilometry, the quality of the unwrapped phase is determined by the high-frequency carrier. Thus, working with only one binary pattern, one can use a single defocusing level (low) in order to reduce the data acquisition time and maintain the quality of the unwrapped phase. Experimental results are presented to verify the success of the proposed method.
2 citations