Abstract: In order to improve the performance of laser phase-shift range finder, a Mach-Zehnder modulator is used as external modulator of the range finder, and the modulation frequency is increased to obtain high distance resolution. A phase-shift ranging system is described. In the system, the sinusoidal modulation signals about 1.5 GHz is generated by a fractional-N frequency synthesizer, and the Mach-Zehnder modulator working as an intensity modulator is used. The phase difference drift caused by temperature is eliminated with differential measurement method, and the phase-shift is obtained with a heterodyne technique associated with cross-correlation analysis. The experimental results show that the phase difference drift caused by the photoelectric detector and circuit noise is less than 0.15°, and the distance error of the ranging device is within ±0.05 mm .

Key words: differential measurement, Mach-Zehnder modulator, phase difference drift, phase-shift range finding, Analytical algorithm, Forward kinematics analysis, Parallel mechanisms, Sensor