Journal
OPTICS AND LASERS IN ENGINEERING
Volume 52, Issue -, Pages 19-26Publisher
ELSEVIER SCI LTD
DOI: 10.1016/j.optlaseng.2013.07.007
Keywords
Speckle; Phase measurement; Vortices; Multi-level spiral phase filters; Spatial light modulators
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A multi-level spiral phase filter is proposed in electronic speckle pattern interferometry (ESPI) for out-of-plane displacement measurements. This filter generates a particular kind of speckle pattern that results from the convolution of standard speckles with the filter point spread function (Fourier transform). We shall refer to it as a vortex-filtered speckle pattern (VF-SP). It is shown here that if unresolved and fully developed VF-SPs are generated, then each speckle contains embedded phase terms which can be controlled by the multi-level spiral filter rotation. This mechanism effectively allows the application of standard phase extraction procedures for displacement measurements. Numerical simulations of an interferometer working with VF-SPs were done to verify this technique. Experimental validation was achieved with an out-of-plane electronic speckle pattern interferometer, in which an Liquid Crystal on Silicon (LCoS) was used to generate the multi-level spiral phase filters. (C) 2013 Elsevier Ltd. All rights reserved.
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