27 May 2003 Mechanical measurement using multiplexing/demultiplexing of digital Fresnel holograms
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Proceedings Volume 4933, Speckle Metrology 2003; (2003) https://doi.org/10.1117/12.516666
Event: Speckle Metrology 2003, 2003, Trondheim, Norway
We propose a multiplexing/demultiplexing technique in digital Fresnel holography for the simultaneous measurement of two dimensional deformations. The spatial multiplexing uses the incoherent mixing of 2x2 coherent waves. The optical arrangement of the setup gives access simultaneously to the out of plane and the in plane component of the displacement field. For this, we use a twin polarizing Mach-Zehnder interferometer which produces the simultaneous incoherent addition of two holograms of the object. The digital holograms are reconstructed using the discrete Fresnel transform. Each object phase encodes the in plane and out of plane component of the displacement field vector. In order to exract the mixing of the 2D measurement, we use a spatial demultiplexing of the holograms. Its principle is based on the use of the spatial autocorrelation function. The spatial coordinate of one of its three lobes is used for the demultiplexing of the second hologram on the first. This numerical demultiplexing is based on the two dimensional Fourier transform and the application of the so called delay theorem. After demultiplexing, the sum of the two phase change gives access to the out of plane component and their difference to the in plane one. Experimental results dealing with the study of the mechanical behavior of composite materials are presented.
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Pascal Picart, Pascal Picart, Eric Moisson, Eric Moisson, D. Mounier, D. Mounier, } "Mechanical measurement using multiplexing/demultiplexing of digital Fresnel holograms", Proc. SPIE 4933, Speckle Metrology 2003, (27 May 2003); doi: 10.1117/12.516666; https://doi.org/10.1117/12.516666

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