Robust phase-unwrapping algorithm for flat measurement in phase-stepping interferometry

Chunlong Wei; Mingyi Chen; Weidong Hou; Hongwei Guo; Zhijiang Wang

doi:10.1117/12.318442

10 August 1998 Robust phase-unwrapping algorithm for flat measurement in phase-stepping interferometry

Chunlong Wei, Mingyi Chen, Weidong Hou, Hongwei Guo, Zhijiang Wang

Proceedings Volume 3558, Automated Optical Inspection for Industry: Theory, Technology, and Applications II; (1998) https://doi.org/10.1117/12.318442
Event: Photonics China '98, 1998, Beijing, China

Abstract

Phase-stepping interferometry has been extensively applied in optical metrology. But the phases calculated by the phase-stepping algorithm are wrapped into the range [-it, it] because of the arctangent function. The procedure of recovering the real phase from thd range [-it, it] is known as phase-unwrapping. The phase unwrapping may be a trivial problem with the cases of noisy, low modulation, corrupted regions etc. in the interferograms. The conventional algorithm always failed in those cases. Many algorithms were developed to solve the problem. A new phase unwrapping algorithm is proposed by our group. It is very suitable for the flat measurement. The new algorithm first fits the measured flat data to an ideal flat by a group of new formulas derived by ourselves. Then do operation of plus or minus 2it for the wrapped phases calculated by phase-stepping algorithm according to the ideal flat. Since the measured flat data do not affect each other in the phase unwrapping procedure, the conventional phase unwrapping problem is avoided. A flat metal plane is measured with many corrupted regions in a Linnik interference microscope. The experimental results indicate that our new algorithm is robust and fast.

Citation Download Citation

Chunlong Wei, Mingyi Chen, Weidong Hou, Hongwei Guo, and Zhijiang Wang "Robust phase-unwrapping algorithm for flat measurement in phase-stepping interferometry", Proc. SPIE 3558, Automated Optical Inspection for Industry: Theory, Technology, and Applications II, (10 August 1998); https://doi.org/10.1117/12.318442

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KEYWORDS

Phase shift keying

Phase interferometry

Algorithm development

Interferometry

Phase measurement

Metals

Microscopes

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