Fig. 1. Schematic diagram of general structure of laser Doppler vibrometer

Fig. 2. Schematic diagram of optical path for vibration measurement based on pupil-plane interferometry

Fig. 3. Comparison of Doppler signals of tuning fork vibration. (a) Optical path for vibration measurement based on image-plane interferometry; (b) optical path for vibration measurement based on pupil-plane interferometry

Fig. 4. Instantaneous velocity extraction for signal in Fig.3(b). (a) Wavelet time-frequency energy diagram; (b) wavelet ridge extraction diagram; (c) velocity curve diagram

Fig. 5. Experimental setup of vibration measurement system based on pupil-plane interferometry

Fig. 6. Velocity measurement curves of two instruments in random vibration experiment

Fig. 7. Distribution of measurement difference and measurement mean

Fig. 8. Linear fitting results of vibration frequency and peak velocity

Fig. 9. Measurement results of complex vibration frequency