在光子计数模式的激光雷达应用中,回波信号的动态范围大。激光雷达的远场回波信号处于探测器的线性输出区间,无需进行校准;近场信号基本处于探测器的非线性响应区,需要进行校准。为了提高远场信号的信噪比,提出了一种校准方法。依据脉冲激光雷达方程,使用远场信号反演得到修正的近场信号,并与接收的回波信号作比较,得到校准因子。进一步使用校准因子修正前后的数据分别反演了能见度,并与能见度仪的探测结果作比较。结果显示:对于未修正的数据,远场信号反演与能见度仪得到的能见度平均偏差和标准差分别为0.57 km和1.89 km,而近场信号的平均偏差大于10 km。由修正后的数据得到的能见度与能见度仪的结果符合得很好,平均偏差和标准差分别为0.43 km和0.76 km。

The echo signals have a large dynamic range in the applications of photon counting mode lidar. The far-field echo signals of lidar are within the linear output range of detectors and thus no calibration is required. However, because the near-field signals are usually within the non-linear response area of detectors,it is necessary to calibrate the near-field signals. In order to improve the signal-to-noise ratio of far-field signals, a novel calibration method is proposed. According to the pulsed lidar equation, the corrected near-field signals are obtained by the retrieval of the far-field signals, and simultaneously are compared with the received echo signals to obtain a calibration factor. The data before and after correction by this calibration factor are further used to retrieve the visibility, respectively, which is compared with the detection results obtained by the visibility sensor. The results show that, for the uncorrected data, the average deviation and standard deviation between the visibility obtained by the far-field signals and that by the visibility sensor are 0.57 km and 1.89 km, respectively, while the average deviation exceeds 10 km for the near-field signals. The visibility obtained from the corrected data is in a good agreement with that by the visibility sensor. The average deviation and standard deviation are 0.43 km and 0.76 km, respectively.