Fig. 1. Grid discrete case

Fig. 2. Treatment of rough surface with inverted triangle and downward folding

Fig. 3. Observation point deployment and reference frame schematic

Fig. 4. Surface longitudinal displacement nephogram at time 1μs

Fig. 5. Comparison of longitudinal displacements at different distances from the center point along the X direction

Fig. 6. Comparison of longitudinal displacements at different distances from the center point along the Y direction

Fig. 7. Comparison of displacement responses in different directions

Fig. 8. Comparison of longitudinal displacements at 1 mm from the center under three excitation modes

Fig. 9. Comparison of longitudinal displacements at 2 mm from the center under three excitation modes

Fig. 10. Comparison of longitudinal displacements at 4 mm from the center under three excitation modes

Fig. 11. Experimental principle of laser transient grating excitation aluminum plate

Fig. 12. Experimental device layout and excitation - detection light circuit diagram

Fig. 13. The original displacement data of transient grating excitation

Fig. 14. Comparison between measured and simulated data of observation point displacement