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Proceedings Paper

Measurements of aspheric surfaces
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Paper Abstract

A newly developed interferometer for characterization of aspheric surfaces is presented. The interferometer is based on the Fizeau configuration and uses a sub-Nyquist CCD camera as a detector. Due to the camera design, the instrument is capable of recording very dense fringe patterns of up to 4 fringes/pixel. This enables processing of interferograms with hundreds of fringes in the field of view. Thus, the interferometer can be used to measure many types of aspheric surfaces using a standard transmission sphere as a reference. However, the main obstacle associated with this kind of interferometer is caused by the presence of so called "re-trace" errors, which can be significant. Such errors occur from un-equal optical paths the reference and test beams travel through in the optical system of the interferometer. A ray tracing procedure has been developed to subtract the influence of the optical system of the interferometer on the measurement. This method of error compensation results in reducing measurement errors to λ/5 PV (peak to valley) for the full range of fringe densities with the low order aberrations not exceeding λ/10. We present measurements of test surfaces illustrating the effectiveness of the error compensation procedures as well as preliminary measurements of multiple aspheric surfaces.

Paper Details

Date Published: 11 August 2008
PDF: 9 pages
Proc. SPIE 7063, Interferometry XIV: Techniques and Analysis, 706317 (11 August 2008);
Show Author Affiliations
Piotr Szwaykowski, Engineering Synthesis Design (United States)
Raymond Castonguay, Engineering Synthesis Design (United States)

Published in SPIE Proceedings Vol. 7063:
Interferometry XIV: Techniques and Analysis
Joanna Schmit; Katherine Creath; Catherine E. Towers, Editor(s)

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