New algorithm of white-light phase shifting interferometry pursing higher repeatability by using numerical phase error correction schemes of pre-processor, main processor, and post-processor

• Published in: Optics and lasers in engineering Vol. 46; no. 2; pp. 140 - 148
• Main Authors: Kim, Jung-Hwan, Yoon, Sung-Won, Lee, Jeong-Ho, Ahn, Woo-Jung, Pahk, Heui-Jae
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.02.2008; Elsevier
• Subjects: Exact sciences and technology; Fundamental areas of phenomenology (including applications); Image reconstruction; tomography; Imaging and optical processing; Instruments, apparatus, components and techniques common to several branches of physics and astronomy; Interferometers; Numerical correction; Optical instruments, equipment and techniques; Optics; Phase error; Physics; White-light phase shifting interferometry; White-light phase shifting interferometry; Numerical correction; Phase error; Light interferometry; Positioning; White light; Phase shifting interferometry; Theoretical study; Measuring methods; Numerical method; Mechanical vibrations; Image reconstruction; Repeatability; Image analysis; Algorithms; Error correction; Least square fit
• ISSN: 0143-8166; 1873-0302
• DOI: 10.1016/j.optlaseng.2007.08.008

White-light phase shifting interferometry (WLPSI) is frequently used for the precision measurement of 3D patterns in various fields. Phase error is one of the most dominant errors in WLPSI, and it is mainly generated by the scanner positioning error and mechanical vibrations. In this paper, phase error detection method by image analysis is proposed, and the numerical correction method for minimizing the phase error is also proposed. The image reconstruction method (IRM), iterative IRM (IIRM) as pre-processors, partial IRM (PIRM), least squares method (LSM) as a main processor, and surface compensation method (SCM) as a post-processor were developed for correcting phase errors. The five methods are implemented and simulated, and the pros and cons of each method are explained. Mirau type interferometry and the phase error generator using a PZT stage were used, and the measurements by WLPSI were done under various vibration conditions. The captured images were analyzed by the five correction methods, and the results were compared. Phase error was effectively minimized by the correction methods, and repeatability of 0.2 nm was obtained in the case of the specimen of 500 nm in height. Repeatability of 10 nm was obtained by conventional WLPSI algorithms for the same specimen.