Fig. 1. Schematic diagram of laser doppler velocimetry principle

Fig. 2. Structure diagram of optical system

Fig. 3. Detail between the beam and the target

Fig. 4. Signal acquisition diagram. (a) Original signal; (b) sampling points at 200 K~280 K; (c) sampling points at 280 K~300 K; (d) original signal spectrum

Fig. 5. Signal processing flow chart

Fig. 6. Physical picture of the optical path

Fig. 7. Original signal diagrams of (a) channel 1 and (b) channel 2

Fig. 8. Spectrum diagrams of signals in (a) channel 1 and (b) channel 2

Fig. 9. (a) FFT logarithmic amplitude spectrum and (b) refine framing logarithmic amplitude spectrum

Fig. 10. Time frequency diagrams under different framings. (a) N=5 K; (b) N=2 K; (c) N=1 K; (d) N=0.5 K; (e) N=0.25 K; (f) N=0.2 K；

Fig. 11. Change in beam’s angle

Fig. 12. Speed component of (a) channel 1 and (b) channel 2 and (c) the combined speed

Fig. 13. Detailed v-t diagram after (a) frame dividing demodulation and (b) STFT demodulation

Fig. 14. Velocity measurement values at different beam angles

Fig. 15. v-t diagram of (a) channel 1; (b) channel 2 and (c) the combined speed during acceleration

Fig. 16. v-t diagram (a) before and (b) after algorithm modification

Fig. 17. Comparison of RMSE before and after filtering