A dual-frequency continuous wave doppler lidar for velocity measurement at far distance

A dual-frequency continuous wave Doppler lidar for long-distance and high-precision velocity measurement is experimentally demonstrated in this article. The lidar system uses the optical heterodyne detection method to avoid complicated optical coherent configuration. All Phase Fast Fourier Transform and Chirp-Z Transform are used to obtain the Doppler frequency shift. The maximum of the calculated Doppler shift was 999.83 Hz with the frequency resolution of 0.54 Hz, and the corresponding theoretical velocity was determined to be 749.87 m/s. During the experiment, the speed of the car was successfully measured in the outdoor environment, the frequency and velocity resolutions were less than 0.5 Hz and ± 0.2 m/s, respectively, and the detection distance of moving and stationary targets reached 1100 m and 2300 m. The capability of the dual-frequency Doppler lidar system has been verified.