The simultaneous quantitative measurement of out-of-plane displacement and slope using the fast Fourier transform method with a single three-aperture digital speckle pattern interferometry (DSPI) arrangement is demonstrated. The method coherently combines two sheared object waves with a smooth reference wave at the CCD placed at the image plane of an imaging lens with a three-aperture mask placed in front of it. The apertures also introduce multiple spatial carrier fringes within the speckle. A fast Fourier transform of the image generates seven distinct diffraction halos in the spectrum. By selecting the appropriate halos, one can directly obtain two independent out-of-plane displacement phase maps and a slope phase map from the two speckle images, one before and the second after loading the object. It is also demonstrated that by subtracting the out-of-plane displacement phase maps one can generate the same slope phase map. Experimental results are presented for a circular diaphragm clamped along the edges and loaded at the center.
"shows the schematic of double aperture spatial phase-shift shearography setup introduced by B. Bhaduri et al in 2006 <ref type="bibr" target="#b5" coords="4,484.94,404.05,32.28,11.09;4,63.00,415.58,20.04,11.09"></ref> . In this setup, the diffuse object is illuminated by a collimated laser beam. "
[Show abstract][Hide abstract] ABSTRACT: A direct method of determining second-order derivatives of displacement (curvature and twist) using two-channel double-aperture digital shearography is presented. Spatial carrier fringes are incorporated inside the speckle using a double-aperture mask in a two-channel experimental setup. Two sets of slope phase maps are generated that are either shifted in the x direction for curvature measurement or in the y direction for twist measurement. Experimental results are presented to verify the validity of the proposed method.
[Show abstract][Hide abstract] ABSTRACT: In this paper, we report the investigations undertaken towards mapping the slope of specularly reflecting bent plates using moiré deflectometry. Towards improvement of the measurement characteristics, the four-step phase shifting technique has been incorporated into the deflectometric setup to obtain quantitative results. The experimental verification of the proposed technique for poly-methyl methacrylate (PMMA) specimens in the form of a cantilever beam and a circular plate, subjected to a well-defined load, has been undertaken. In each case, the experimental results match well with theoretical predictions.
Journal of Modern Optics 06/2012; 59(11):1-7. DOI:10.1080/09500340.2012.697199 · 1.01 Impact Factor
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