为检测微弱超声振动信号,设计了一个具有较高检测灵敏度的光学外差干涉系统。采用相干性高的线偏振光作为光源,提高了有效干涉强度;利用光阑消除光学噪声,并有效控制回授光对光路的影响;最后,以1级光作为参照光,使光路调节简单易行。实验结果显示,用主频为62.42 kHz、幅值为74 V的方波信号激励超声探头作为振动信号源时,测得的振动信号频率和幅值分别为62.38 kHz和76.4 mV,表明该系统能满足微弱超声振动检测要求。

In order to detect weak ultrasonic signal,a high-sensitivity optical heterodyne interferometer was developed.A linearly polarized laser with good coherence was used as light source to improve interference intensity,and a diaphragm was employed to eliminate the optic noises and the influences of feedback lights on the light path.Then,the system was easily adjusted by using the 1 st order light as reference light.Experimental results indicate that the measured vibration signal frequency and amplitude are 62.38 kHz and 76.4 mV respectively,when a square wave is adopted to excite the ultrasonic probe with 62.42 kHz central frequency and 74 V amplitude,which shows proposed system can satisfy the detection requirement of weak ultrasonic signal.