卫星激光测距(Satellite Laser Ranging，SLR)常利用激光大气后向散射所形成的图像来引导光束指向，而光束图像亮度随天区变化的现象在SLR站普遍存在，影响了激光对卫星的瞄准。以中国科学院上海天文台现有SLR系统为研究平台，阐明了该现象的成因，即光束图像成像光路中分光镜的效率会随偏振方向改变而变化。据此提出偏振方法，通过建立出射激光偏振方向随望远镜位置变化模型，改变发射光路中新引入半波片的角度，实现了光束图像于不同亮度的实时控制。相比使用消偏振分光镜的方案，该方法具有应用灵活、系统简单且成本低的优势，研究成果在提高激光对卫星的瞄准精度及星象图像信噪比等方面具有重要意义。

Laser beam image generated by atmosphere backscattering has been widely used to monitor the laser pointing in Satellite Laser Ranging(SLR). The phenomenon that the brightness of beam image differs from sky sections influences the satellite aiming. Based on the SLR system of Shanghai Astronomical Observatory, Chinese Academy of Sciences, the mechanism of this phenomenon was figured out that the efficiency of splitter mirror was generally related to the polarization state of incident light. Accordingly, a new method was proposed that a half-wave plate was deployed in transmitting path, and rotating it realized the real-time control of different brightness for beam imaging. The model of outgoing laser polarization direction with the pointing of telescope was established. Compared with the use of splitter mirror whose efficiency is independent of polarization direction, the method is more flexible, simpler and less cost. The method can be applied in improving laser beam pointing accuracy in SLR and Signal-to-Noise Ratio(SNR) of star image etc.