激光超声振动是在纳米级的微振动,受环境噪声的影响比较大,且使用传统方法得到的探测信号强度太低,不利于检测。针对这个问题,使用组合双凸透镜对激光进行聚焦,提高探测信号的强度,并设计了具有较高灵敏度的双光路差分干涉系统,将参考信号与探测信号的强度差控制在理想范围内。实验结果表明,探测信号的强度可达到648 mV,与传统方法相比有10倍左右的提升,解调出的振动信号失真度较小,信噪比可达32.1 dB,提升了近5倍。与传统方法相比,各项性能有了较大提升。

Laser ultrasonic vibration is a micro-vibration at nanometer level, which is heavily impacted by environmental noise, and the intensity of detection signal of traditional methods is too low to detect. In order to solve this problem, a double optical path system of differential interference is developed, which has a high sensitivity. By using a combination of lenticular lens to focus the light, the detection signal intensity is improved and the intensity difference between the reference signal and the detection signal within a preferably range is controlled. The experimental results show that, compared with traditional methods, the intensity of detection signal can be achieved 648 mV, raising about 10 times, and the demodulated signal distortion is smaller, signal noise ratio(SNR) can be 38.1, raising about 5 times. In general, the performance of the system developed has been greatly improved compared with traditional methods.