光学外差干涉法检测激光超声振动

Detection of Laser Ultrasonic Vibration Using Optical Heterodyne Interferometry

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648m V,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。

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 w as 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 intensitydifference between the reference signal and the detection signal within a preferably range. T h e experiments show that,compared with traditional methods,the intensity of detection signal can be achieved 6 48 mV,raising about 10 times, and the distortion of demodulated signal is smaller, signal noise ratio ( S N R ) can be 115, the displacementresolution of the system can reach 0. 03 nm.