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Proceedings Paper

Testing an optical window of a small wedge angle
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Paper Abstract

Multiple reflections between two surfaces of a window introduce a fixed pattern error in the transmitted wavefront. In a Fizeau or Twyman-Green interferometer, this wavefront is reflected by a return flat and transmits through the window. The fixed pattern error is carried in the measurement result. This error is negligible, only if the wedge angle is so large that the interference fringes formed by the two surfaces are too dense for the detector to resolve. However, if the wedge angle is small (e.g., several arc-seconds), the phase error (pv) could be up to 0.025 fringes for most glass (n equals 1.5). By tilting both the window and the return flat properly, it is possible to cancel the effect of multiple reflections of a window.

Paper Details

Date Published: 1 February 1994
PDF: 9 pages
Proc. SPIE 1994, Advanced Optical Manufacturing and Testing IV, (1 February 1994); doi: 10.1117/12.167979
Show Author Affiliations
Chiayu Ai, WYKO Corp. (United States)
James C. Wyant, WYKO Corp. (United States)

Published in SPIE Proceedings Vol. 1994:
Advanced Optical Manufacturing and Testing IV
Victor J. Doherty D.V.M., Editor(s)

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