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18 April 2013 Fast phase shifting shadow moiré by utilizing multiple light sources
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We present a fast phase shifting shadow moiré device for the measurement of surface topography. In our set-up, the phase shift across the field of view shadow moiré is introduced by using two light sources illuminate the grating sequentially. Therefore, it is possible to capture the two fringe patterns at high speed. Due to the effect of bias modulation, the proposed phase demodulation method first removes the DC term of the sampling data. Then a spiral phase transform (SPT) based technique is developed to determine the introduced phase shift pointwisely. After that, the tunable two-frame algorithm is used to extract the wrapped phase map with no spatially non-uniform phase shift error. We implemented a fast technique to determine the topography of a surface by a simple experimental set-up. The proposed technique was applied to obtain an external surface of a specimen. The experimental results show the validity of this technique.
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Hubing Du, Hong Zhao, and Bing Li "Fast phase shifting shadow moiré by utilizing multiple light sources", Proc. SPIE 8681, Metrology, Inspection, and Process Control for Microlithography XXVII, 86812A (18 April 2013);


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