在外场用已知半球反射率的靶板作为标准靶板,反演测定目标靶板激光雷达散射截面和半球反射率。由于受到随机变化的大气衰减和激光器输出能量等因素的影响,靶板角分布曲线与朗伯余弦曲线会有一定偏差,因此,采用双光路测量法来确定各个测量时刻的大气衰减系数和激光器输出能量,然后,再与半球反射率已知的标准靶板比较,计算得到目标靶板的激光雷达散射截面。实验测得的目标靶板反射率为24.9%,与实际标定值25.3%的相对误差为1.6%,满足10%的外场精度要求。通过实验测量的结果分析表明利用双光路方法对目标靶板与标准靶板进行测量,较好地消除了各个时刻的大气衰减和激光器照射能量对测量结果的影响。

Using a plate whose hemisphere reflectivity is known as a standard plate, the lidar scattering cross section (LRCS) and hemisphere reflectivity of a target plate are measured inversely. Because of the influence of the random fluctuation of the atmospheric attenuation coefficient and the laser′s lasing energy, there are deviations between the scattering voltage angular distribution curves and the lambert cosine curve. Therefore, the two-channel and relative measurement method is adopted to determine the atmospheric attenuation coefficient and the lasing energy. Then the lidar scattering cross section of the target plate can be calculated by comparing with that of the standard plate. The experimental value of the target plate′s hemisphere reflectivity is 24.9%, the real value of it is 25.3%, the relative error is 1.6%, which satisfies the accuracy requirements of outfield test. The experimental results indicate that the influence of the random fluctuation of atmospheric attenuation coefficient and laser′s lasing energy on the test results can been washed away very well by using the two-channel and relative measurement method.