Paper
1 February 1994 Testing an optical window of a small wedge angle
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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.
© (1994) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Chiayu Ai and James C. Wyant "Testing an optical window of a small wedge angle", Proc. SPIE 1994, Advanced Optical Manufacturing and Testing IV, (1 February 1994); https://doi.org/10.1117/12.167979
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KEYWORDS
Wavefronts

Interferometers

Optical testing

Fizeau interferometers

Glasses

Phase measurement

Sensors

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