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Quadrature-detection-error Compensation in a Sinusoidally Modulated Optical Interferometer Using Digital Signal Processing

Hwang, Jeong-hwan;Park, Chang-Soo

  • Received : 2019.03.28
  • Accepted : 2019.04.26
  • Published : 2019.06.25

Abstract

In an optical interferometer that uses sinusoidal modulation and quadrature detection, the amplitude and offset of the interference signal vary with time, even without considering system noise. As a result, the circular Lissajous figure becomes elliptical, with wide lines. We propose and experimentally demonstrate a method for compensating quadrature detection error, based on digital signal processing to deal with scaling and fitting. In scaling, fluctuations in the amplitudes of in-phase and quadrature signals are compensated, and the scaled signals are fitted to a Lissajous unit circle. To do so, we scale the average fluctuation, remove the offset, and fit the ellipse to a unit circle. Our measurements of a target moving with uniform velocity show that we reduce quadrature detection error from 5 to 2 nanometers.

Keywords

Optical interferometer;Quadrature detection error compensation;Quadrature fringe measurement error;Quadrature detection

Acknowledgement

Supported by : GIST