双纵模He-Ne激光器的多普勒测速系统

Laser Doppler velocimeter based on dual-longitudinal-mode He-Ne laser

为了进行高速及超高速测量,提出了一种基于双纵模He-Ne激光器的多普勒测速结构。阐述了双纵模激光多普勒测速的基本原理,设计了系统的光路结构,并运用数字滤波、数字自相关技术对多普勒信号进行处理。理论分析与实验结果表明:双纵模激光多普勒测速系统利用相邻两个纵模的拍频作为基频大大减小了比例因子,解决了系统进行高速及超高速测量的难题;数字滤波去除直流基底和部分噪声;自相关技术进一步抑制噪声,提高了信噪比,便于精确提取多普勒频率。测量了高速转盘上待测点切向运动的速度,测量结果的重复性精度优于0.8%。

In order to make the measurement for high speed and super speed, a novel structure of Doppler velocimeter based on the dual-longitudinal-mode He-Ne laser was proposed. The principle of the dual-longitudinal-mode laser Doppler velocimeter was expounded while the optical schematic of the system was designed. And the Doppler signal was processed using the digital filtering and autocorrelation. Results of the theory analysis and experiment show that the dual-longitudinal-mode laser Doppler velocimeter reduced the scale factor highly using the beat frequency of the adjacent two longitudinal- modes as the basic frequency and solved the problem of high speed and super speed measurement; basement and part of noise are get rid of with the help of the digital filter; noise is restrained further with the method of digital autocorrelation so that the signal-to-noise ratio is raised and the Doppler frequency is extracted easily. The tangential velocity of the measured point in the rotating disc was obtained and the reoeatabilitv of the results was good to 0.8%.