Laser Altimeter Based on Random Code Phase Modulation and Heterodyne Detection

A novel laser altimetry method with a long-range detection and high spatial resolution is proposed. The proposed method is based on random code phase modulation and heterodyne detection. The application of random code removes the pulselength restriction. Coarse and accurate measurements are combined in the signal process. In the proof-of-concept experiment, the range resolution and range accuracy are estimated at ±0.15 and ±0.075 m, respectively, in the free space target, under a signal power of 0.29 nW, local oscillator power of 1 mW, modulation rate of 100 MHz, sampling rate of 1 GHz, and pulselength of 80 μs.