Heterodyne Doppler velocity measurement of moving targets by mode-locked pulse laser

In this study, heterodyne detection is adopted to measure the velocity of a target simulated by a rapidly rotating plate by using a modelocked pulse laser as the resource. The coherent beat frequency of the signal light reflected by target and local oscillation light occurred on the surface of the detector. Then the waveform of beat frequency was processed by filtering to obtain the Doppler frequency shift of the signal light induced by target. With this frequency shift, the velocity of target could be obtained by calculation. Results indicate that the measurement has a high precision. The error on average is within 0.4 m/s.