不同通量条件下光子计数激光雷达信号畸变的规律研究

Research on signal distortion of photon counting lidar under various flux conditions

摘要:

光子计数激光雷达在高通量条件下的输出信号会出现严重的畸变现象,从而影响目标信息的提取,因此,研究信号畸变的变化规律是一个重要的理论与实践问题。为此本文建立了多触发条件下光子计数激光雷达信号计算的稳态正向递推模型,该模型具有精度高、速度快,且可准确反映物理过程等显著优势。结合正确性验证,通过改变模型的信号幅度N、脉冲宽度PW、背景噪声Nb和死区时间Td等参数对激光雷达信号畸变的影响规律进行探究,结果表明:当死脉比Rdp≤2时,信号的畸变与N、PW、Td有关,当Rdp>2时,信号畸变仅与N有关；同时在仿真实验结果中发现,当探测损失率α≤5%时,可忽略信号畸变的影响,该发现可作为区分高通量信号畸变(α>5%)与低通量信号保真(α≤5%)的判别界限,根据计算,在某些特定条件下,改变死区时间的大小会将高通量转化为低通量。上述结论相比于传统的基于光子计数率的“5%”准则更加精确地划分了高低通量与信号畸变的界限。

Abstract:

The output signal of photon counting lidar has serious distortion phenomenon under the high-flux condition,which affects the extraction of target information.Therefore,to investigate the change rule of signal distortion,this paper establishes the steady-state forward recursion model for signal calculation of photon counting lidar under the condition of multi-trigger.The model has many advantages,such as high precision,fast speed and accurate reflection of physical process.The influence of the echo signal distortion is explored by changing the signal amplitude N,the pulse width PW,the background noise Nb and dead time Td of the model.Results show that when the dead-pulse-ratio Rdp≤2,the signal distortion is related to N,PW and Td,when Rdp>2,the signal distortion is only related to N.At the same time, our simulations show that when the detection loss rate α≤5%,the influence of signal distortion can be ignored, which can be used to distinguish high-flux signal distortion (α>5%) and the fidelity of the low-flux signal (α≤5%).According to the calculation,changing the length of the dead time converts the high-flux to the low-flux under some specific conditions.Compared with the traditional "5%" criterion based on photon count rate,the above conclusion provides a more accurate boundary between the high-and low-flux and signal distortion.