Yan Liping, Chen Zhouqiang, Chen Benyong, Xie Jiandong, Zhang Shihua, Lou Yingtian, Zhang Enzheng
Opt Express. 2018 Feb 19;26(4):4818-4831. doi: 10.1364/OE.26.004818.
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.
提出了一种用于由正弦和三角信号组合调制的零差干涉仪的精密PGC解调方法。使用三角信号作为附加调制，无论被测物体处于静止还是运动状态，都能产生用于椭圆拟合的连续相移干涉信号。可以实现PGC解调中正交分量的交流幅度和直流偏移的实时椭圆拟合与校正。这种调制的优点是能够彻底消除由光强扰动、调制深度漂移、载波相位延迟以及传统PGC解调中低通滤波器的非理想性能等影响所导致的周期性非线性。详细描述了采用组合调制信号进行信号处理的原理与实现。进行了椭圆拟合精度和速率评估、纳米及毫米位移测量的实验，以验证所提解调方法的可行性。实验结果表明，正交分量的椭圆参数能够实时精确获取，并且在位移测量中实现了纳米级精度。
