Displacement measurement with multi-level spiral phase filtering in speckle interferometry

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• 作者：Alberto Aguilar ; Abundio D¨¢vila ; J.E.A. L ; grave
• 关键词：Speckle ; Phase measurement ; Vortices ; Multi-level spiral phase filters ; Spatial light modulators
• 刊名：Optics and Lasers in Engineering
• 出版年：2014
• 出版时间：January, 2014
• 年：2014
• 卷：52
• 期：Complete
• 页码：19-26
• 全文大小：1943 K

文摘

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.