28 November 2011 Robust digital speckle photography based on radon and Fourier-Mellin transforms
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We present a new and robust method for determining in-plane displacements of an object from distorted Digital Speckle Photography (DSP) images. This new approach is designed particularly to facilitate accurate measurement of deformations of steel samples during a gas quenching heat treatment process, where rigid body motion and large deformations lead to unwanted image distortions. The new method allows the computation and correction of image rotation and magnification via Radon and Fourier-Mellin Transformations prior to calculations of in-plane displacements, thereby alleviating the inaccuracy that arises from the cross correlation of distorted images in conventional DSP. The method is validated through simulation and measurements with predefined deformations. Initial studies show that the new method is well suited for this application and that it enables measurement of displacements with high accuracy in the micrometer range.
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E. N. Kamau, C. Falldorf, C. von Kopylow, and R. B. Bergmann "Robust digital speckle photography based on radon and Fourier-Mellin transforms", Proc. SPIE 8202, 2011 International Conference on Optical Instruments and Technology: Solid State Lighting and Display Technologies, Holography, Speckle Pattern Interferometry, and Micro/Nano Manufacturing and Metrology, 82020A (28 November 2011); doi: 10.1117/12.904375; https://doi.org/10.1117/12.904375


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