• Title/Summary/Keyword: Homodyne interferometerl

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Measurement and Compensation of Nonlinearity in Homodyne Interferometer (Homodyne 간섭계에서의 비선형성 측정과 보정)

  • Kim, Jong-Yun;Eom, Tae-Bong;Jeong, Kyu-Won;Choi, Tae-Young;Lee, Keon-Hee
    • Journal of the Korean Society for Precision Engineering
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    • v.18 no.9
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    • pp.171-178
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    • 2001
  • The nonlinearity of a laser interferometer usually ranges from sub-nanometer to several manometers. This nonlinearity, which has periodic characteristics, limits the accuracy of the interferometer at the sub-nanometer level. The nonlinearity error of the one-frequency homodyne interferometer with quadrature fringe detection results from a number of factors including polarization mixing by imperfect optical elements, unequal gain of photo detectors, lack of quadrature between two signals and misalignment. In this paper, we described a method for measuring and compensating the nonlinearity of homodyne interferometer using the elliptical fitting technique with least-square method. Experimental results demonstrate that $^\pm$3.5 nm nonlinearity can be reduced to $^\pm$0.2 nm level.

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