Fourier processing of shearing interferometric fringe patterns

Hansuk Lee; Lewis S. Wang; Sridhar Krishnaswamy

doi:10.1117/12.269832

20 March 1997 Fourier processing of shearing interferometric fringe patterns

Hansuk Lee, Lewis S. Wang, Sridhar Krishnaswamy

Proceedings Volume 2921, International Conference on Experimental Mechanics: Advances and Applications; (1997) https://doi.org/10.1117/12.269832
Event: International Conference on Experimental Mechanics: Advances and Applications, 1996, Singapore, Singapore

Abstract

We describe a compact shearing interferometric system for the measurement of full-field stress distributions of optically isotropic, transparent structures. Design of the system is based on the consideration that the analysis of the experimental data should be automated so as to obtain results with high spatial resolution and high accuracy. To this end, a specially designed Wollaston prism is used to generate a pair of spatially displaced beams when the prism is illuminated by a collimated laser beam. The two sheared and orthogonally polarized versions of the laser beam interfere with each other by the use of an analyzer. In addition, the special prism can also generate a set of parallel and equally spaced carrier fringes in the interference pattern of the shearing interferometer. The presence of the carriers greatly facilitates the analysis of the fringe patterns obtained in the interferometer when a Fourier transform phase measurement technique is applied. Experiments performed include several specimens with different configurations and materials, namely: (1) a homogeneous PMMA specimen with a crack; (2) a PMMA/aluminum bi-material specimen with an interfacial crack and (3) a PMMA/aluminum bi-material specimen with a sub- interfacial crack. Results obtained from the Fourier analysis technique are in good agreement with those from finite element method.

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Hansuk Lee, Lewis S. Wang, and Sridhar Krishnaswamy "Fourier processing of shearing interferometric fringe patterns", Proc. SPIE 2921, International Conference on Experimental Mechanics: Advances and Applications, (20 March 1997); https://doi.org/10.1117/12.269832

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KEYWORDS

Fringe analysis

Polymethylmethacrylate

Prisms

Fourier transforms

Interferometry

Finite element methods

Collimation

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