Micro-profile measurement of a transparent coating using windowed Fourier transform in white-light vertical scanning interferometry

Suodong Ma; Chenggen Quan; Rihong Zhu; Lei Chen

doi:10.1117/12.970532

15 October 2012 Micro-profile measurement of a transparent coating using windowed Fourier transform in white-light vertical scanning interferometry

Suodong Ma, Chenggen Quan, Rihong Zhu, Lei Chen

Author Affiliations +

Proceedings Volume 8417, 6th International Symposium on Advanced Optical Manufacturing and Testing Technologies: Optical Test and Measurement Technology and Equipment; 841725 (2012) https://doi.org/10.1117/12.970532
Event: 6th International Symposium on Advanced Optical Manufacturing and Testing Technologies (AOMATT 2012), 2012, Xiamen, China

Abstract

Owing to free of the phase ambiguity problem, white-light vertical scanning interferometry (WLVSI) is commonly used to inspect surface profiles of objects, especially for the micro-profile measurement of microelectromechanical systems (MEMS) devices. Although numerous algorithms have been proposed for the white-light interference signal analysis, most of them focused only on test objects with a single reflective surface. In this paper, a technique to measure the micro-profile of a transparent coating using windowed Fourier transform in WLVSI is described. A windowed Fourier filtering (WFF) operation is first adopted to roughly estimate the local peak positions of a recorded interference signal. Subsequently a least-square estimation based on the retrieved phase values of a filtered signal is separately applied into previously extracted local peak positions to achieve more accurate micro-profile results. The thickness of the coating can be finally estimated by the retrieved reflective surfaces. Experimental works, conducted on a flat plate and a MEMS device with a transparent coating on its substrate, demonstrate the validity of the proposed method.

Citation Download Citation

Suodong Ma, Chenggen Quan, Rihong Zhu, and Lei Chen "Micro-profile measurement of a transparent coating using windowed Fourier transform in white-light vertical scanning interferometry", Proc. SPIE 8417, 6th International Symposium on Advanced Optical Manufacturing and Testing Technologies: Optical Test and Measurement Technology and Equipment, 841725 (15 October 2012); https://doi.org/10.1117/12.970532

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