Color deflectometry for phase retrieval using phase-shifting methods

In this paper, we propose a technique based on a color fringe pattern used on deflectometry experiment. The advantages of using color fringe patterns together with phase shifting techniques on deflectometry experiment are presented. An experimental wavefront reconstruction of a progressive lens shows the accuracy and simplicity of these techniques used to process the deflection measurements. � 2014 Elsevier Ltd. All rights reserved

Measurement of phase objects by the use of color phase-shifting technique

A simple technique for wavefront measurement is presented. This technique is based on the use of a computer display (LCD monitor) to generate color fringe patterns, which are imaged by a single-CCD color camera; whereas a phase object is placed in the ray path for imaging. The ray de ections distort the image of the pattern. By measuring this distortion, the gradients of the phase change caused by the object can be obtained. For the evaluation of the acquired fringe patterns, we use a classical phase-shifting technique with three fringe patterns encoded in a single color image displayed by the monitor; therefore, this proposed technique allows for real-time object shape measurement. Experiments are presented to demonstrate the success of this technique. � 2013 Copyright SPIE

Wavefront recovery Fourier-based algorithm used in a vectorial shearing interferometer

Vectorial Shearing Interferometer is able to select variable shear and tilt along any wavefront direction. This system is self-referenced and with variable sensibility. We proposed this instrument to measure a phase object without rotational symmetry. Phase recovery is implemented by a Fourier-based algorithm and spatial unwrapping methods. We show results emphasizing the advantage in the easier selection of fringe density and directional derivative orientation for a speci c optical element. © 2013 Copyright SPIE

3D Shape measurement with binary phase-shifted technique and digital filters

Shape measurements by sinusoidal phase-shifting methods require high-quality sinusoidal fringes. Furthermore, most of the video projectors are nonlinear, making it difficult to generate high quality phase without nonlinearity calibration and correction. To overcome the limitations of the conventional digital fringe projection techniques, we proposed a method that involves the projection of digital binary patterns generated by the pulse-width modulation (PWM). We will demonstrate that applying digital filtering, in particular, low pass filters, one can obtain a high-quality sinusoidal pattern. Which in combination with phase-shifting methods, allows a reliable 3-D profiling surface reconstruction at large timerates. Validation experiments using a commercial video projector are presented. © 2014 SPIE