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为解决远距离处人工地震波的检测问题,研究了光源的相干性,系统的稳定性,激光多普勒信号强度、信噪比,位移测量灵敏度和精度等理论及方法。采用在腔内插入两个直径为1.8mm的可变光阑和输出光的准直结构(4倍),增大光源的相干长度和可测距离;在两路光中分别加入声光调制器和λ/4波片,实现偏振态匹配并使系统工作更稳定,提高信噪比;采用透镜聚焦接收,增大信号强度;采用特伦逆向反射装置,消除它在位移或振动过程中因偏摆或横移所带来的影响,使测量灵敏度和精度提高约一倍。将此系统用于2m处的振动进行原理性实验,其振幅测量相对误差为0.1%,可测频率最高为750Hz,因此可用于高空遥测人工地震波。
In order to solve the problem of detection of artificial seismic waves at long distances, the theories and methods of light source coherence, system stability, laser Doppler signal intensity, signal-to-noise ratio, displacement measurement sensitivity and accuracy are studied. In the cavity into the two variable aperture 1.8mm diameter and output light collimation structure (4 times), increase the coherence length of the light source and measurable distance; in the two-way light were added acousto-optic modulator And λ / 4 wave plate to achieve the polarization state matching and make the system more stable and improve the signal to noise ratio; using lens focus to receive and increase the signal strength; using Tron retroreflector to eliminate it in the process of displacement or vibration due to partial Pendulum or the impact of horizontal movement, the measurement sensitivity and accuracy of about doubled. This system is used for the principle experiment of vibration at 2m. The relative error of amplitude measurement is 0.1%, and the highest measurable frequency is 750Hz. Therefore, it can be used in the teleseismic artificial seismic wave.