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Proceedings Paper

Dynamic focal spots registration algorithm for freeform surface measurement
Author(s): Wenjiang Guo; Liping Zhao; I-Ming Chen
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Paper Abstract

In a wavefront sensing system, the raw data for surface reconstruction, either the slope matrix or curvature matrix, is obtained through centroiding on the focal spot images. Centroiding is to calculate the first moment within a certain area of interest, which encloses the focal spot. As the distribution of focal spots is correlated to the surface sampling condition, while a uniform rectangular grid is good enough to register all the focal spots of a uniformly sampled near flat surface, the focal spots of aspherical or freeform surfaces have varying shapes and sizes depending on the surface geometry. In this case, the normal registration method is not applicable. This paper proposed a dynamic focal spots registration algorithm to automatically analyze the image, identify and register every focal spot for centroiding at one go. Through experiment on a freeform surface with polynomial coefficients up to 10th order, the feasibility and effectiveness of the proposed algorithm is proved.

Paper Details

Date Published: 22 June 2013
PDF: 9 pages
Proc. SPIE 8769, International Conference on Optics in Precision Engineering and Nanotechnology (icOPEN2013), 876911 (22 June 2013); doi: 10.1117/12.2021107
Show Author Affiliations
Wenjiang Guo, National Metrology Ctr., A*STAR (Singapore)
Nanyang Technological Univ. (Singapore)
Liping Zhao, National Metrology Ctr., A*STAR (Singapore)
I-Ming Chen, Nanyang Technological Univ. (Singapore)

Published in SPIE Proceedings Vol. 8769:
International Conference on Optics in Precision Engineering and Nanotechnology (icOPEN2013)
Chenggen Quan; Kemao Qian; Anand Asundi, Editor(s)

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