为了提高激光测距的精度与稳定性，通过改良传统相位激光测距仪，设计了新型正交调制降频与最小二乘法解相位的相位式激光测距仪。使用反射镜实现内外测距光路，通过正交调制技术对发射激光进行幅度调制，接收模块接收到的回波信号经过混频器后再经过低通滤波器将回波信号降频，降低解相难度并提升解相精度。改用分时测量得到距离相位从而消除二次混频方法所产生的附加相移，分别对内外光路低频回波信号采样进行模数转换后使用最小二乘法求解相位。采用多频率调制测量兼顾激光测距范围与测量精度，最后通过超定方程解模糊算法求解多频测距的待测距离。在国家标准基线上进行样机测试，实验结果表明，在60 m量程内正交调制激光测距仪的测量平均误差控制在1.5 mm以内，测距量程内标准差保持在0.9 mm以内。

A novel laser range finder method based on the quadrature modem and least square method was investigated to improve the accuracy and reliability of traditional portable phase laser range finders. A reflector was employed for inner and outer optical paths. After amplitude modulation of laser intensity by the quadrature modulation method, the echo signal was mixed with modulation signal and passed through a low-pass filter to reduce the frequency, thus simplifying phase detection and improving solution accuracies. The inner and outer phase shifts were used to eliminate the additional phase shift lead by the secondary mixing. The low frequency echo signal from the inner and outer optical path were sampled for analog to digital conversion respectively, then the phase was solved base on the least square method. Multi-frequency measurement was adopted to maintain the laser ranging range and measurement accuracy. Finally, the measured distance was obtained by solving the laser ranging ambiguity by overdetermined linear equation. The proposed range finder was experimented on the national standard baseline. The results show that the prototypes of those rangers exhibit an average measurement error less than 1.5 mm and an standard deviation less than 0.9 mm in the range of 0~60 m.