可靠准确的参考光检测是提高直接测距型激光主动成像系统测距精度的关键因素之一, 对基于PIN探测器的参考光检测电路设计进行了深入研究。首先, 对比分析了雪崩光电二极管(APD)和PIN光电二极管性能及其供电电路的难度。综合考虑参考光功率稳定特性及参考光光路设计难度, 选择PIN探测器进行激光雷达参考光检测。详细分析了高压集成芯片LT3482作为常规电源和利用电流监测模式驱动PIN探测器时的差别。选择高增益带宽积跨阻放大器OPA657N实现PIN探测器电流电压转换, 对其关键外围元件参数的选取进行了详细分析。同时介绍了超高速比较器MAX9601的应用注意事项。最后, 设计了电路板并进行实验验证。结果表明: 对脉冲为10 ns的激光光源, 当PIN探测器施加89.449 V的偏置电压时, 其输出电流信号经跨阻放大器后电压幅值达到-3.7 V, 可保证起始信号可靠检出, 但脉冲展宽为15 ns。整个模块可有效给出参考光对应的计时起始信号。基于集成高压芯片驱动的PIN探测器配合恒定阈值时刻鉴别方法在直接测距型激光主动成像系统参考光检测中是切实可行的。

Accurate detection of reference beam was one of the key factors to enhance the ranging accuracy in the laser active imaging system with direct ranging. The circuit design of detection of reference beam based on PIN detector was researched in detail. Firstly, the comparative analysis of performance and difficulty of power supply circuit between avalanche photodiode(APD) and PIN photodiode was conducted. Considering the power stability and designing difficulty of the reference beam, the PIN detector was selected to detect the reference beam in ladar. Two modes including normal power and current monitor existed in LT3482, and the difference when used to drive PIN detector was analyzed deeply. The transimpedance amplifier OPA657N with high gain-bandwidth product was used to convert the current of PIN detector to voltage, and the selection method of key external components was introduced. Also, points for attention in usage of MAX9601 were given. At last, the circuit was designed for experimental verification. The results show that voltage converted from the current of PIN detector through transimpedance amplifier is -3.7 V when the pulse width of laser is 10 ns and bias voltage applied to the PIN detector is 89.449 V. The pulse width of voltage is extended to be 15 ns, but the starting signal is ensured to be detected. The timing discrimination signal according to the reference beam could be given effectively by the module. PIN detector based on integrated high-voltage chip combined with constant threshold timing discrimination was feasible in direct ranging laser active imaging system detection of reference beam.