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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648mV,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32.1dB,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 micro-vibration in the nanoscale, which is greatly affected by environmental noise, and the detection signal intensity obtained by the traditional method is too low, which is unfavorable to the detection. In order to solve this problem, a combination of lenticular lenses is used to focus the laser beam to improve the intensity of the detection signal. A dual optical differential interference system with high sensitivity is designed to control the intensity difference between the reference signal and the detection signal within the ideal range. Experimental results show that the intensity of the detection signal can reach 648mV, which is about 10 times higher than that of the traditional method. The distortion of the demodulated vibration signal is small, the signal-to-noise ratio is up to 32.1dB and the gain is nearly 5 times. Compared with the traditional method, the performance has been greatly improved.