高精度宽测速范围精确方向判别单模VCSEL自混合LDV

High precision and wide dynamic range single mode VCSEL self-mixing LDV system with exactly direction discrimination

单模VCSEL(Vertical cavity surface emitting laser)激光器自混合LDV(Laser Doppler veloci- tymeter)系统的温度特性和外腔长度L_(ext)(激光器前腔镜到目标散射面之间的光程)可变范围优于多模激光器LDV系统。应用差频模拟锁相环信号处理技术,明显提高了单模VCSEL自混合LDV测速精度和测速动态范围.用多普勒频移f_d的分频跟踪三角波电流调制技术,提高了运动方向判别的精度和动态范围.实验结果表明,在外腔长度为30mm±3mm、温度为0℃～55℃、采样时间0.1s、激光器无温控的条件下,分辨率优于0.2%;在测速范围为30～480mm/s的条件下,测速精度优于1%;在速度范围为5～480mm/s的条件下,测速精度优于2%.在电源电压为5V时,正向运动方向指示电平大于4.9V,反向运动方向指示电平小于0.1V.

The self-mixing laser Doppler velocitimeter （LDV） system using single mode vertical cavity emitting laser （VCSEL） has better temperature characteristics and wider external cavity length （the optical path length from the laser front mirror to target plate） range compared with the system using multi-mode laser diode. Difference frequency analog phase locked loop （PLL） for small signal processing was used and it obviously improved the velocity measurement accuracy. Triangular wave modulation according to which frequency is divided by the Doppler frequency fd for direction discrimination was used and it improved its accuracy and dynamic range. The experimental results are as follows： when external length is 30±3 mm, temperature range is 0 ℃-55 ℃ （no temperature controller for VCSEL）, sampling time is 0.1 s, the velocity measurement resolution is better than 0.2% and when velocity measurement range is 30-480 mm/s, the accuracy is better than 0.1% and when the measurement range is 5-480 mm/s, the accuracy is better than 2%. When the supply voltage is 5 V, the forward direction indicating level is higher than 4.9 V and the backward level is lower than 0.1 V.