A novel displacement demodulation method of a laser interferometer for primary vibration calibration

A displacement demodulation method of a laser interferometer based on quadrature demodulation and subdivi-sion demodulation is proposed for the primary vibration calibration. The quadrature demodulation applies qua-druplicated frequency and direction identification to demodulate the coarse displacement signals, whose result is regarded as the integer part of the displacement value, while the subdivision demodulation employs anti-tangent transformation to demodulate the fine displacement signals, whose result is regarded as the fractional part of the displacement value. The proposed method not only can obtain the vibration amplitude and phase, but also can increase the resolution ratio of the displacement value by the subdivision demodulation, and besides the down -sampling output for the acquisition data dramatically reduce the demodulation data. The experimental results obtained from the proposed method have a good consistence with that from the sine approximation method in the primary vibration calibration.