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Proceedings Paper

Model-free optical surface reconstruction from deflectometry data
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Paper Abstract

Deflectometry is a metrology method able to measure large surface slope ranges that can achieve surface reconstruction accuracy similar to interferometry, making it ideal for freeform metrology. While it is a non-null method, deflectometry previously required a precise model of the unit under test to accurately reconstruct the surface. However, there are times when no such model exists, such as during the grinding phase of an optic. We developed a model-free iterative data processing technique which provides improved deflectometry surface reconstruction of optics when the correct surface model is unknown. The new method iteratively reconstructs the optical surface, leading to a reduction in error in the final reconstructed surface. Software simulations measuring the theoretical performance limitations of the model-free processing technique as well as a real-world test characterizing actual performance were performed. The method was implemented in a deflectometry system and a highly freeform surface was measured and reconstructed using both the iterative technique and a traditional non-iterative technique. The results were compared to a commercial interferometric measurement of the optic. The reconstructed surface departure from interferometric results was reduced from 44.39 μm RMS with traditional non-iterative deflectometry down to 5.20 μm RMS with the model-free technique reported.

Paper Details

Date Published: 14 September 2018
PDF: 8 pages
Proc. SPIE 10742, Optical Manufacturing and Testing XII, 107420Y (14 September 2018); doi: 10.1117/12.2320745
Show Author Affiliations
L. R. Graves, College of Optical Sciences, The Univ. of Arizona (United States)
H. Choi, College of Optical Sciences, The Univ. of Arizona (United States)
W. Zhao, Institute of Optics and Electronics (China)
C. J. Oh, College of Optical Sciences, The Univ. of Arizona (United States)
P. Su, ASML Corp. (United States)
T. Su, KLA-Tencor Corp. (United States)
D. W. Kim, College of Optical Sciences, The Univ. of Arizona (United States)
Steward Observatory, The Univ. of Arizona (United States)

Published in SPIE Proceedings Vol. 10742:
Optical Manufacturing and Testing XII
Ray Williamson; Dae Wook Kim; Rolf Rascher, Editor(s)

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