Wavefront reconstruction of discontinuous phase objects from optical deflectometry

One of the challenges in phase measuring deflectometry is to retrieve the wavefront from objects that present discontinuities or non-differentiable gradient fields. Here, we propose the integration of such gradients fields based on an Lp-norm minimization problem. The solution of this problem results in a nonlinear partial differential equation, which can be solved with a fast and well-known numerical methods and doesn't depend on external parameters. Numerical reconstructions on both synthetic and experimental data are presented that demonstrate the capability of the proposed method

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

A Variational Model for Wrapped Phase Denoising

This paper presents a variational model for the denoising of wrapped phase images. By enforcing the required Pythagorean trigonometric identity between the real and imaginary components of the signal, this model improves the signal-to-noise ratio of the restored signal. To preserve phase map discontinuities, the model is based on total variation. The existence and uniqueness of the model’s solution are demonstrated using standard techniques. In addition, the convergence of a rapid fixed-point method to determine the numerical solution is demonstrated. Experiments on both synthetic and actual patterns validate the model’s performance

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

Improvement of least-squares integration method with iterative compensations in fringe reflectometry

Least-squares integration is one of the most effective and widely used methods for shape reconstruction from gradient data, which result from gradient measurement techniques. However, its reconstruction accuracy is limited due to the imperfection of the Southwell grid model, which is commonly applied in the least-squares integration method. An operation with iterative compensations is therefore proposed, especially for the traditional least-squares integration method, to improve its integration accuracy. Simulation and experiment are carried out to verify the feasibility and superiority of the proposed operation. This compensatory operation with iterations is suggested, and its good performance on integration accuracy improvement is shown.Published versio