Open AccessPrecision PGC demodulation for homodyne interferometer modulated with a combined sinusoidal and triangular signal
Author(s) -
Liping Yan,
Zhouqiang Chen,
Benyong Chen,
Jiandong Xie,
Shihua Zhang,
Yingtian Lou,
Enzheng Zhang
Publication year - 2018
Publication title -
optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.26.004818
Subject(s) - demodulation , optics , direct conversion receiver , ellipse , signal (programming language) , interferometry , physics , phase modulation , modulation (music) , homodyne detection , interference (communication) , acoustics , computer science , channel (broadcasting) , telecommunications , phase noise , astronomy , programming language
A precision PGC demodulation for homodyne interferometer modulated with a combined sinusoidal and triangular signal is proposed. Using a triangular signal as additional modulation, a continuous phase-shifted interference signal for ellipse fitting is generated whether the measured object is in static or moving state. The real-time ellipse fitting and correction of the AC amplitudes and DC offsets of the quadrature components in PGC demodulation can be realized. The merit of this modulation is that it can eliminate thoroughly the periodic nonlinearity resulting from the influences of light intensity disturbance, the drift of modulation depth, the carrier phase delay, and non-ideal performance of the low pass filters in the conversional PGC demodulation. The principle and realization of the signal processing with the combined modulation signal are described in detail. The experiments of accuracy and rate evaluations of ellipse fitting, nanometer, and millimeter displacement measurements were performed to verify the feasibility of the proposed demodulation. The experimental results show that the elliptical parameters of the quadrature components can be achieved precisely in real time and nanometer accuracy was realized in displacement measurements.