激光多普勒检波系统的研究

Study on demodulation system of laser Doppler

为了进一步提高地震检波器的指标 ,研究了激光多普勒测量方法和微弱信号检测技术等 ,设计出了一种LD做光源的差动式激光多普勒检波系统 ,此系统采用高斯光束聚焦、大口径透镜接收 ,能接收到很强的多普勒信号 ,并且具有高的空间分辨力 ,同时 ,采用声光调制技术及锁相放大技术 ,提高了信号的信噪比 ,其结构简单、紧凑 ,装调方便 ,光能利用率和空间分辨力高 ,可测频率范围为 0 .5Hz～ 10 0 0Hz ;振幅范围为 2 μm～ 5mm ;频率测量精度为 0 .6 % ;振幅测量精度为 1%

To improve the specifications of seismometers,laser Doppler measurement technique and weak signal detect technology and etc are studied,and a differential Doppler demodulation system with a LD is designed.In this system,more Doppler signals are received and more space resolving power are achieved because of adopting Gaussian beams focus and lens with large diameter as well as acoustooptic modulation technology and lock-in amplifier used to improve SNR.It has characteristics of simple structure,fixing and adjusting convenience,high use-ratio of light power and space resolution.The measurable ranges of frequency and amplitude are 0.5Hz～1000Hz, 2μm～5mm respectively,and the corresponding measurement precisions are 0.6%,1% respectively.