20 May 2009 Interferometric measurement method of thin film thickness based on FFT
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The kernel of modern interferometry is to obtain necessary surface shape and parameter by processing interferogram with reasonable algorithm. The paper studies the basic principle of interferometry involving 2-D FFT, proposes a new method for measuring thin film thickness based on FFT: by CCD receiving and acquired card collecting with the help of Twyman-Green interferometer, can a fringe interferogram of the measured thin film be obtained. Based on the interferogram processing knowledge, an algorithm processing software/program can be prepared to realize identification of the edge films, regional extension, filtering, unwrapping the wrapped phase etc. And in this way can the distribution of film information-coated surface be obtained and the thickness of thin film samples automatically measured. The findings indicate the PV value and RMS value of the measured film samples are 0.256 λ and 0.068 λ respectively and prove the new method has high precision.
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Gaolong Shuai, Junhong Su, Lihong Yang, Junqi Xu, "Interferometric measurement method of thin film thickness based on FFT", Proc. SPIE 7283, 4th International Symposium on Advanced Optical Manufacturing and Testing Technologies: Optical Test and Measurement Technology and Equipment, 72832K (20 May 2009); doi: 10.1117/12.828717; https://doi.org/10.1117/12.828717

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