针对单个光弹调制器((Photoelastic Modulator，PEM))干涉具受到材料本身热、力学的限制，产生的最大光程差小，而多个PEM串联又难以控制，且多个PEM界面的多次反射将使光能大量损失等缺点，提出一种在单PEM上贴全反射膜经过多次反射有效提高最大光程的方法。理论推导分析了不同反射情况对光程差的影响，并得到任意角任意位置入射经多次反射后产生最大光程差的公式与光谱反演公式，且通过COMSOL、MATLAB、ZEMAX仿真和实验验证其可行性。实验选用的弹光晶体为硒化锌(ZeSe)，压电晶体为石英，结果显示实验与理论的相对误差为0.21%，为该方法的工程应用提供了参考。

Single photoelastic modulation (PEM) interferometer has the limitation of thermal and mechanical in the material, so the modulated optical path difference is small, however, series PEMs are difficult to control, and the multiple reflections of various PEM interface make the energy of light lost. Therefore, a method of effectively improving optical path difference by multiple reflections was put forward, based on one single PEM posted on the total reflection film. By deducing and analyzing the influence of the different reflective situation on the optical path difference, the formula of the optical path difference was got after multiple reflections of incidence in arbitrary angle and position. The method was proved by COMSOL, MATLAB, ZEMAX simulations and experiments. The adopted photoelastic crystal was ZeSe and the piezoelectric crystal was quartz. Result shows that the relative error of experiment and theory is 0.21%, which provides the theoretical basis for the engineering application of this method.