Fig. 1. Experimental apparatus

Fig. 2. Laser ultrasonic propagation path

Fig. 3. B-scan of light sources with different diameters

Fig. 4. Comparison of theoretical and experimental arrival time of each echo

Fig. 5. B-scan of aluminum alloy plates with different thickness

Fig. 6. Comparison of laser ultrasonic directivity

Fig. 7. Typical laser ultrasonic A-scan signal

Fig. 8. Directivity diagram of sound field related to light source diameter

Fig. 9. Longitudinal wave field distribution of 10 mm aluminum alloy plate

Fig. 10. Longitudinal wave beam width of aluminum alloy plates with different thickness

Fig. 11. Transverse wave sound field distribution of aluminum alloy plate

Fig. 12. Transverse wave beam width of aluminum alloy plates with different thickness