Laser ultrasonic vibration is a micro-vibration at nanometer level.which is heavily impacted by envi-ronmental 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 was developed,which has a high sensitivity, and proposed to use a combination of lens to focus the light,improving detection signal intensity and controlling the in-tensity difference between the reference signal and the detection signal within a preferably range. The experiments show that, compared with traditional methods.the intensity of detection signal can be achieved 648 mV .raising about 10 times.and the distortion of demodulated signal is smaller, signal noise ratio( SNR) can be 115 , the displacement resolution of the system can reach 0. 03 nm.%激光超声振动是在纳米级别的微弱振动,受环境噪声的影响比较大,且使用传统方法所得到的探测信号强度太低,不利于检测,系统信噪比也比较低.针对这个问题,使用组合透镜对激光进行聚焦,提高探测信号强度,并设计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.实验结果表面,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115.该系统对位移的分辨率可达0.03 nm.
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