The traditional technique of phase laser range finder is mixing high frequency signals with analog circuits and filtering
them to obtain the useful signal with low frequency. But the analog mixing circuits are susceptible to interference and
will bring amplitude attenuation, phase jitter and offset and this way has difficulties in achieving high precision ranging
and fast speed ranging at the same time. The method of this paper is based on under-sampling technique with digital
synchronous detection and referring to Digital down converter technique of digital IF receiver in radar system. This
method not only reduces the complexity of data processing, improves the speed and accuracy of phase detection at the
same time, but also reduces requirements for ADC devices and DSP chips in the ladar system by a lower sampling rate.
At the same time, the structure of electronic system is global simplified compared with traditional analog ladar system
and the anti-jamming is greatly enhanced. So this method has important research value.