Coherent moire technique for obtaining slope and curvature of stress patterns
01 Oct 1994-Optical Engineering (International Society for Optics and Photonics)-Vol. 33, Iss: 10, pp 3359-3363
TL;DR: In this paper, a method for studying the stress-induced birefringence over the area of a sample by simultaneous application of shearing interferometry and moire techniques is dealt with.
Abstract: A method for studying the stress-induced birefringence over the area of a sample by simultaneous application of shearing interferometry and moire techniques is dealt with. This is a method by which one can have the fringe pattern for the first and second derivative of the birefringence distribution in the form of the slope and curvature of the test wavefront. There is, however, a method of obtaining the second derivative fringe system by using a four-exposure holographic technique in which the pattern is generated by shearing of two holograms of deformed surface. This is related to stress distribution in the structure under test. In the presented method, on the other hand, the test wavefront carries the information of stress distribution in terms of birefringence. The suggested experimental setup can provide the slope and curvature of the test wavefront in a single exposure.
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TL;DR: Keywords: fringe analysis Reference EPFL-ARTICLE-176959doi:10.1016/j.optlaseng.2012.04.006View record in Web of Science URL: http://www.sciencedirect.com/science/article/pii/S0143816612001182
105 citations
TL;DR: Simulation and experimental results are presented to demonstrate the ability of the proposed method in accurately providing the direct estimation of the unwrapped distributions corresponding to the interference phase and its derivatives in a computationally efficient manner.
Abstract: Analysis of strain and the study of flexural moments of a deformed object is of utmost importance in non-destructive testing and evaluation. In digital holographic interferometry (DHI), this information is provided, respectively, by the first and second-order derivatives of the interference phase. This paper introduces high-order instantaneous moments based approach for the simultaneous measurement of displacement, strain and curvature distributions of a deformed object in DHI. Simulation and experimental results are presented to demonstrate the ability of the proposed method in accurately providing the direct estimation of the unwrapped distributions corresponding to the interference phase and its derivatives in a computationally efficient manner.
17 citations
TL;DR: In this paper, a coherent moire technique is used to study the first derivative of a stress pattern using birefringence properties, which is very similar to holographic techniques as both produce second order fringes.
Abstract: In photoelastic investigations, one uses the property of stress induced birefringence for stress analysis. Normal polariscopes are used for such studies. However, the accuracy of the methods is low. For better accuracy, interferometric and holographic methods are generally used. Holography, along with a shearing technique, is also used to obtain partial derivatives of displacement with respect to spatial co-ordinates. In these methods, the resultant fringe pattern is obtained from the mutually shifted holograms and the generation of such patterns requires four exposures altogether. The present paper represents a method based on a coherent moire technique for studying the first derivative of a stress pattern using birefringence properties. The analysis seems to be very similar to holographic techniques as both produce second order fringes. The advantage of this method is that it requires only one exposure. The basic principle as well as some experimental results are presented.
7 citations
TL;DR: In this paper, a confocal microscopic setup with a pair of birefringent lenses having their crystal axes crossed is used to measure phase down to the order of /10.
Abstract: A confocal microscopic setup with a pair of birefringent lenses having their crystal axes crossed is used to measure birefringence of thin samples. The method can be used to measure phase down to the order of /10. The fast and slow axes of the object also can be identified. The principle of the method along with the experimental setup is described. Some first-order experimental results are also presented.
6 citations
TL;DR: In this paper, the linear fringe pattern generated by a lateral shear interferometer using a Wollaston prism is made incident on the GRIN sample and the profile is measured from the deflection of the fringes.
4 citations