激光成像系统高精度目标距离和强度信息提取

Target-distance and intensity information detecting with high precision in laser imaging system

为提高脉冲激光3D成像系统中提取目标距离和强度信息的精度,对时刻鉴别和峰值保持电路进行了深入研究。在简要分析激光测距体制及探测器选择的基础上,给出了激光3D成像系统结构框图:激光器输出信号经半反半透棱镜,反射光线触发参考APD作为计时起始信号,以提高计时基准。给出了恒定阈值鉴别与恒比定时鉴别相结合的时刻鉴别电路,在提高时刻鉴别精度的同时可有效消除噪声对电路的影响。峰值保持选取基于OPA861的跨导型峰值保持电路。在实验室搭建了回波信号模拟系统,并在此基础上对电路性能进行测试。最后,给出了实验结果。结果显示:时刻鉴别电路精度优于1ns;当输入窄脉冲峰值信号低于800mV时,峰值保持电路保持精度优于2.63%。整个结果满足后续实验要求。

In order to enhance the precision of target distance and intensity information in pulse laser 3D imaging system, the time-discriminating circuit and peak holding circuit were studied in detail. Based on analyzing the laser distance-detecting method and the selection of detector, the principle diagram of pulse laser 3D imaging system was given. In this system, pulse from laser was sent to transflective prism, and the reflected light triggered reference APD. Output signal from the reference APD was selected as starting signal for timing to enhance timing basic. Constant threshold discriminator and constant fraction discriminator were combined to form the timing discriminator. In this method, high precision of timing discriminator could be achieved while eliminating the effect of noise to the circuit. The transconductance circuit based on OPA861 was selected to hold the peak signal. The APD signal simulating system was constructed in laboratory, and performance of those circuits were tested. At 1 ast, testing result was given. Result shows that the precision of time discriminating circuit is better than 1 ns and the precision of peak holding circuit is better than 2.63% when the peak value of narrow pulse signal is less than 800 inV. The result can satisfy the requirement of latter experiment.