用于机载激光雷达偏振通道增益比测量的1／2波片优化设计

Optimized design of 1/2 retardation sheet for measurement of airborne lidar polarization channels gain ratio

利用平面平行板模型和晶体膜层理论,定量分析了偏振光通过1/2波片时偏振平行分量和偏振垂直分量透过率的比值与晶体厚度的关系,对用于机载激光雷达偏振通道增益比测量的1/2石英波片和1/2方解石波片的最佳加工厚度和合适的厚度加工区域进行了定量计算和探讨,指出了不适合加工的晶体厚度区域。回波信号的偏振化方向与1/2波片的光轴方向平行和垂直时分别测得的增益比值存在一定的差异,利用这两个增益比值反演得到的沙尘退偏振比,其最大相对误差在20%左右。

The relation between ratio of parallel and perpendicular polarization components of the airborne lidar＇s polarized backscatted signals and crystal thickness are analyzed quantitatively using plane parallel plate pattern and crystal membranous theory when the polarized lights permeate 1/2 retardation sheet. Optimal processing thickness and appropriate processing thickness ranges of 1/2 quartz retardation sheet and 1/2 calcite retardation sheet for measurement of airborne lidar polarization gain ratio values are analyzed quantitatively and discussed. At the same time, unfitted processing thickness ranges are pointed out. There are some differences between gain ratios measured respectively when the polarized direction of return signal is parallel or perpendicular with the optical axis of 1/2 retardation sheet. The maximum relative error of dust depolarization ratios inversed using the above gain ratios is about 20 %.