提出一种利用多次全反射共光程外差干涉技术测量微小应力的光学方法。将一个具有两种偏振状态(s偏振与p偏振)的外差光源入射，通过光栅产生+1阶衍射光，光栅受拉应力的拉伸使周期发生变化，+1阶衍射光发生角度偏移。+1阶衍射光入射至长条棱镜内产生全反射，造成s偏振光与p偏振光之间相位差的变化，将该相位差代入推导得到的光栅应力关系中即可求出拉应力。利用棱镜内多次全反射可提高测量精度。根据模拟测量结果可得，入射角为-5°、光栅周期为10 μm、全反射次数为30时，拉应力对相位的灵敏度为1.500 N/(°)，解析度为0.015 N。该方法具有结构简单、测量快速、灵敏度高及不受外界干扰等优点。

An optical method to measure micro-stress based on common-path heterodyne interference technology via multiplet total reflections is presented. A heterodyne light beam with two polarization states (s-polarization and p-polarization) is incident on a grating, the first-order diffraction light is generated. Because the grating is stretched by stress, its period changes thus the first-order diffractive angle has offset. Then, the first-order diffraction beam enters a strip prism and total reflection occurs, which cause the variation in phase difference between the s-polarized and the p-polarized light. By substituting the phase difference into the derived grating stress equation, the stress can be calculated. The measurement accuracy can be improved by multiple total reflections inside the prism. According to the simulation results, when the incidence angle is -5°, the grating period is 10 μm, and the number of total reflections is 30, the stress sensitivity to phase is 1.500 N/(°) and the resolution is 0.015 N. This method has such advantages as simple structure, rapid measurement, high sensitivity and free from outside disturbance.