高噪声高精度时间相关单光子测距系统性能研究

Research on Performance of Single Photon Counting Ranging System with High Background Noise and High Resolution

为弥补伪随机码调幅测距系统性能研究的不足,采用可编程逻辑器件实现1GHz和2.5GHz速率的伪随机码发生器。实验系统以50m为测试距离,针对两路伪随机码光子到达时间点,采用快速傅里叶变换算法得到互相关波形。在此基础上,建立互相关波形的数学模型,采用参数估计法,运用马尔可夫技术完成参数迭代,重构距离波形,得到距离估计值。实验结果表明,伪随机码为1的比例为1%,探测到的光子计数率为2×106 s-1;低背景噪声下,积分时间和信噪比成正比,与理论相符;高背景噪声下,随着积分时间的增大,采用该方法估计的距离值标准差比峰值距离标准差的增大速度缓慢,整体距离精度高于峰值距离精度。积分时间为0.001s时,2.5GHz码速测距的精度从7.3cm提高到4.62cm。另外,该方法估计得到的1GHz的距离精度仍然低于2.5GHz的距离精度,同等速率下,可降低噪声对距离精度的影响。

In order to compensate the shortness of the pseudorandom ranging system performance research, pseudorandom generator of 1 GHz and 2.5 GHz is realized by field-programmable gate array. Using 50 m as tested range, two channel photons arriving times are measured and calculated by fast Fourier transformation to obtain cross-correlation wave. Based on that, the cross-correlation mathematic model is set up and the parameter evaluation method is used, Markov technique is utilized to optimize parameter iteration. The cross-correlation wave is reconstructed and the range evaluation value is obtained. The ratio of pseudorandom pattern of 1 is 1% and the detected photon counting rate is 2 × 10^6 s-l. The research result manifests that under low background condition, with the increased integration time, the signal to noise ratio increases, which agrees with the theory result. Under high background condition, with the increased integration time, the deviation amplifying speed with direct peakvalue is greater than the speed with the proposed method. Compared with the peak value method, the whole resolution is improved. With the integration time of 0. 001 s, the resolution is increased from 7.3 cm to 4.62 cm. In addition, the resolution of 1 GHz is much lower than the resolution of 2.5 GHz. At the same bit speed, the effect of background noise on resolution is weakened.