Fig. 1. Schematic of laser ultrasonic nondestructive testing

Fig. 2. Schematic of balanced detection system

Fig. 3. Signal-to-noise ratio simulations under balanced detection and common coherence detection

Fig. 4. General block diagram of experimental system

Fig. 5. Display interface of laser ultrasonic signal detection system

Fig. 6. Experimental testing platform for laser ultrasonic induction and optical coherent detection

Fig. 7. Background noise comparison. (a) Common detection; (b) balanced detection

Fig. 8. Waveforms obtained from laser ultrasonic detection system. (a) Common detection; (b) balanced detection