基于偏振光理论，对线偏振光经光学系统单个或多个元件反射后的偏振变化进行了理论分析: 分析表明，通过适当 调整反射光s、p 分量的振幅系数rs、rp 的值，可使经多个元件后偏振光的偏振度损失小于单个元件; 同时给出了准确确定光束 入射面的方法.在一简易装置上，测得780 nm 高反的两反射镜( 介质膜和银膜) 在偏振角和入射角均为45°时其偏振保偏比分 别为1 000 ∶ 1 和40 000 ∶ 1，且确定了两镜的振幅系数比( rp /rs) 和相位差δ，结果和椭偏仪一致.该方法及装置，一方面可为大 学物理中偏振相关的实验提供理论和实验指导，另一方面可用于科研或工程实际中在线准确测量光学元件或系统的偏振参数( rp /rs ，δ及偏振保偏比) .

Based on the polarized light theory，the polarization change of a linearly polarized light after 　　reflected from one or more optical elements is investigated theoretically. It is found that through appropriately setting 　　the amplitude reflection coefficients ( rs 　　，rp 　　) of optical elements，the polarization deterioration of the polarized light 　　induced by several optical elements can be lower than that induced by one element. A method for determining the 　　incidence plane of a light ray is given. In the experimental setup，the polarization maintaining ratios of two 780 nm high-reflection mirrors ( with dielectric and metallic coatings，respectively) at 45o( for both polarization angle and incidence angle) are determined to be 1 000 ∶ 1 and 40 000 ∶ 1，respectively. The amplitude coefficient ratio rp /rs and phase difference δ are in good agreement with those measured by the ellipsometry. This method and setup can， on the one hand，provide theoretical and experimental guidance for polarization-related physics experiments，and on the other hand，can be applied in scientific research and engineering fields for in-situ measurement of the reflection parameters ( rp /rs and δ) and polarization maintaining ratio of optical elements.