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Proceedings Paper

Choosing a phase-measurement algorithm for measurement of coated LIGO optics
Author(s): Katherine Creath
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Paper Abstract

High precision measurements of nearly flat highly reflective surfaces present many problems when using a phase-measuring Fizeau interferometer. Since a coated reference surface is required to yield good fringe contrast with a high reflectance test surface, the interference fringes are likely to deviate from being perfectly sinusoidal. Utilizing phase-measurement algorithms that take data over a 2-wavelength range of phase shifter motion can help reduce the effects of errors due to nonsinusoidal fringes. If linear and 2nd-order phase shifter errors are present, the greater number of frames of fringe data can aid in making a better estimate of the phase. Eight algorithms that have been published in the literature are compared using simulations and experimental measurements. From this study, it was determined that a 12-frame algorithm having 60° (?/3) phase shifts developed by Surrel had superior performance when used with a Clapham-Dew type coated reference surface and a high reflectance test surface. Residual errors in the phase calculation were found to be reducible to a few thousandths of a wave peak-to-valley.

Paper Details

Date Published: 7 March 2006
PDF: 10 pages
Proc. SPIE 4101, Laser Interferometry X: Techniques and Analysis, (7 March 2006); doi: 10.1117/12.498386
Show Author Affiliations
Katherine Creath, Optineering (United States)

Published in SPIE Proceedings Vol. 4101:
Laser Interferometry X: Techniques and Analysis
Gordon M. Brown; Malgorzata Kujawinska; Werner P. O. Jueptner; Ryszard J. Pryputniewicz; Ryszard J. Pryputniewicz; Mitsuo Takeda, Editor(s)

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