11 October 2010 Study on a novel algorism of phase unwrapping for interferogram processing
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Interferogram processing is one of main techniques in optical interferometry metrology. Modern interferometry for thinfilm thickness has the advantages of noncontact, high accuracy and rich-field, etc. Taking advantage of Twyman-Green interferometer, the relationship between interferogram and thin film thickness parameter can be determined by mathematical model, thus the thickness of thin-film samples is measured automatically. A new algorism of phase unwrapping for measuring the thin-film thickness is proposed based on the FFT method, this algorism identifies a seed point, seed points spread to four points nearby the fist seed point, the four points will serve as the second group of seed points, seed points spread to four points nearby the second group of seed points in turn, pass through all of the effective information points by a diamond path. Seed points will eventually bring about the phase unwrapping in the entire image. The results indicate that the height of the measured film sample, which is processed by the algorism processing software, is 166.3nm. The height is 163nm by using the ZYGO interferometer to process the same sample. This method is superior to the customary one. Although single interferogram was processed in this study, a phase distribution with high accuracy was achieved.
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Jun-hong Su, Jun-hong Su, Wen-bo Wan, Wen-bo Wan, Li-hong Yang, Li-hong Yang, Jun-qi Xu, Jun-qi Xu, } "Study on a novel algorism of phase unwrapping for interferogram processing", Proc. SPIE 7656, 5th International Symposium on Advanced Optical Manufacturing and Testing Technologies: Optical Test and Measurement Technology and Equipment, 765670 (11 October 2010); doi: 10.1117/12.865352; https://doi.org/10.1117/12.865352

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