Fig. 1. Schematic diagram of laser speckle microvibration measurement

Fig. 2. Pig heartbeat and respiration signals extraction based on laser speckle.(a) Extracted heartbeat signal; (b) part of extracted heartbeat signal; (c) extracted respiratory signal; (d) part of extracted respiratory signal

Fig. 3. Flowchart of vibration measurement based on adaptive seed point matching algorithm

Fig. 4. Calculation result of digital image correlation algorithm. (a) Correlation coefficient distribution;

Fig. 5. Flowchart of visual microphone scheme^[17]

Fig. 6. Combined detection scheme of photodiode and spatial light modulator

Fig. 7. Optimization of photodiode detection scheme

Fig. 8. Schematic diagram of experimental setup for line array CCD imaging

Fig. 9. Experimental setup, signal processing procedure, and typical results^[25]

Fig. 10. Average displacement error for different sub-block sizes

Fig. 11. Restoration of single frequency vibration signal by phase correlation method. (a) 300 Hz-1.5 kHz; (b) 3 kHz-7 kHz; (c) 12 kHz-20 kHz

Fig. 12. Laser speckle microvibration signal extraction method based on deep neural network. (a) Structure of neural network; (b) flowchart of data processing

Fig. 13. Schematic diagram of image exposure and readout of a rolling shutter camera^[35]

Fig. 14. Flowchart of signal extraction for Shearlet transform algorithm

Fig. 15. Photographs of the experiment. (a) Cantilever beam; (b) air compressor

Fig. 16. Flowchart of signal extraction