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Proceedings Paper

Asphere cross testing: an exercise in uncertainty estimation
Author(s): Paul E. Murphy
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Paper Abstract

Aspheric surfaces can provide substantial improvements to optical designs, but they can also be difficult to manufacture cost-effectively. Asphere metrology contributes significantly to this difficulty, especially for high-precision aspheric surfaces. With the advent of computer-controlled fabrication machinery, optical surface quality is chiefly limited by the ability to measure it. Consequently, understanding the uncertainty of surface measurements is of great importance for determining what optical surface quality can be achieved.

We measured sample aspheres using multiple techniques: profilometry, null interferometry, and subaperture stitching. We also obtained repeatability and reproducibility (R&R) measurement data by retesting the same aspheres under various conditions. We highlight some of the details associated with the different measurement techniques, especially efforts to reduce bias in the null tests via calibration. We compare and contrast the measurement results, and obtain an empirical view of the measurement uncertainty of the different techniques. We found fair agreement in overall surface form among the methods, but meaningful differences in reproducibility and mid-spatial frequency performance.

Paper Details

Date Published: 16 October 2017
PDF: 10 pages
Proc. SPIE 10448, Optifab 2017, 104481A (16 October 2017); doi: 10.1117/12.2279828
Show Author Affiliations
Paul E. Murphy, QED Technologies, Inc. (United States)

Published in SPIE Proceedings Vol. 10448:
Optifab 2017
Julie L. Bentley; Sebastian Stoebenau, Editor(s)

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