22 June 2015 Modified coherent gradient sensing method for slope measurement of reflective surfaces
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A phase shifting method was developed for Coherent Gradient Sensing (CGS) using a three-step phase shifting method. Three different inteferograms were obtained by changing the distance between two gratings. The phase filed can be calculated accurately from the three inteferograms. The interference fringes (phase field) in reflection mode represent the gradient contours of the out-of-plane displacement of a surface. The curvatures and shape of the surface both can be calculated by numerical methods using the fringe patterns. The measurement principle and experimental setup were introduced in detail. As an application, a standard specimen with a curvature radius of 5 m was measured. From the analysis of the experimental results, we find that the relative error of the curvature using this method was about 0.78%. The method has good potentials for measuring the slopes, curvatures and shapes of thin film/substrate systems.
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Kang Ma, Kang Ma, Huimin Xie, Huimin Xie, } "Modified coherent gradient sensing method for slope measurement of reflective surfaces", Proc. SPIE 9525, Optical Measurement Systems for Industrial Inspection IX, 95251P (22 June 2015); doi: 10.1117/12.2184444; https://doi.org/10.1117/12.2184444

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