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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%。
For high-speed and ultra-high-speed measurement, a Doppler velocimetry structure based on double longitudinal mode He-Ne laser is proposed. The basic principle of dual-mode laser Doppler velocimetry is expounded, the optical structure of the system is designed, and the Doppler signal is processed by digital filtering and digital autocorrelation. Theoretical analysis and experimental results show that the dual-mode laser Doppler velocimetry system uses the beat frequencies of two adjacent longitudinal modes as the fundamental frequency to reduce the scale factor greatly, which solves the difficult problem of high-speed and ultra-high-speed measurement. The digital filtering DC substrate and part of the noise is removed; autocorrelation technology to further suppress noise, improve the signal to noise ratio, easy to accurately extract the Doppler frequency. The tangential velocity of the point to be measured on the high-speed turntable was measured and the repeatability of the measurement results was better than 0.8%.