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Proceedings Paper

Measuring surface slope error on precision aspheres
Author(s): James J. Kumler; J. Brian Caldwell
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Paper Abstract

Optical designers are becoming increasingly aware of the importance of specifying and tolerancing slope errors on optical surfaces, especially aspheric surfaces. Slope errors can degrade system optical performance - in some cases even if the peak to valley surface figure errors meets the optical design tolerance analysis. With this awareness, more optical engineers are putting requirements for peak surface slope on optical element drawings. This puts pressure on optical fabricators to understand slope specifications and react to these requirements, and use the appropriate metrology instrumentation to ensure final system performance. This paper will discuss appropriate ways to specify slope errors, and the challenges and limitations of measuring slope errors with commercial interferometers. The optical designer should be aware of how slope errors are measured on Fizeau interferometers and should specify the spatial intervals of interest when tolerancing aspheric elements. Peak slope error measurement is prone to erroneous measurement errors due to surface contamination, environmental errors, and pupil focus. Finally, filtering has a strong influence on surface slope calculations. Practical examples of slope specifications and experimental results will be presented.

Paper Details

Date Published: 14 September 2007
PDF: 9 pages
Proc. SPIE 6671, Optical Manufacturing and Testing VII, 66710U (14 September 2007); doi: 10.1117/12.753832
Show Author Affiliations
James J. Kumler, Coastal Optical Systems (United States)
J. Brian Caldwell, Caldwell Photographic (United States)

Published in SPIE Proceedings Vol. 6671:
Optical Manufacturing and Testing VII
James H. Burge; Oliver W. Faehnle; Ray Williamson, Editor(s)

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