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10 April 2013 Phase extraction from random phase-shifted shadow moiré fringe patterns using stereovision technique
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The measurement accuracy of phase shifting shadow moiré is limited by the spatially non-uniform and random phase shift error. Substantial work has been developed to overcome this difficulty. But few works are proposed to deal with the two error sources above simultaneously. In the presented paper, we describe a solution that can compensate the both error sources at the same time. In our proposed method, a binocular stereovision system is integrated into our test configuration. By measuring the coordinates of marks attached to the measurement grating, the stereovision system obtains the position and the setting parameters are calibrated. Then, the acquiring three fringe patterns are analyzed by iterative least squares method in temporal and the phase shift is calibrated by the least squares fitting in spatial. Because a local cost function is used, the proposed calibration technique is insensitive to spatial variations in detector response. Numerical simulations and optical experiments show that the proposed method can effectively minimize the two phase-shift error sources and possess a superior performance than the existing typical phase shifting algorithm.
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Feifei Gu, Hubing Du, Hong Zhao, and Bing Li "Phase extraction from random phase-shifted shadow moiré fringe patterns using stereovision technique", Proc. SPIE 8681, Metrology, Inspection, and Process Control for Microlithography XXVII, 868129 (10 April 2013);

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