Algorithm of white-light interferometry for reconstruction of profile

Cheng-Yu Pai; Jiunn-Woei Liaw; Ming Chang

doi:10.1117/12.905133

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15 November 2011 Algorithm of white-light interferometry for reconstruction of profile

Cheng-Yu Pai, Jiunn-Woei Liaw, Ming Chang

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Proceedings Volume 8321, Seventh International Symposium on Precision Engineering Measurements and Instrumentation; 83212Q (2011) https://doi.org/10.1117/12.905133
Event: Seventh International Symposium on Precision Engineering Measurements and Instrumentation, 2011, Yunnan, China

Abstract

An algorithm is proposed to process the interference signals of white-light interferometer in order to obtain the surface height/depth profile of a sample by using the maximum envelope method. Via a low-pass filter, the DC signal of the interference signal is obtained, and then a preprocessed signal which is the difference of the interference signal and its DC one is calculated. After that, the envelope of the preprocessed signal is obtained by using Hilbert transform, and then the height is estimated by the following peak detector. Based on this algorithm, the surface morphology of the sample is reconstructed. In our experiment, a step of 75 nm was set for a PZT motor, the scanning span in z-axis was 10.5 μm, and a 50-fold Mirau interferometer was used. In addition, a polynomial fitting can be used further for the peak detection of this envelope to improve the accuracy. Moreover, a spatial low-pass filter can be utilized to smooth the height profile.

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Cheng-Yu Pai, Jiunn-Woei Liaw, and Ming Chang "Algorithm of white-light interferometry for reconstruction of profile", Proc. SPIE 8321, Seventh International Symposium on Precision Engineering Measurements and Instrumentation, 83212Q (15 November 2011); https://doi.org/10.1117/12.905133

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