利用Zygo干涉仪对斜入射下液晶空间光调制器的纯相位调制特性进行了测量。建立了斜入射下液晶空间光调制器的纯相位调制数学模型,研究了斜入射角度对相位调制特性的影响,搭建了基于Zygo干涉仪的测量系统,对不同入射角度下的相位调制特性进行了测量。测量结果表明:不同入射角度下相位调制量近似线性递增,入射角度越大,相位调制量递增的斜率越小;相同灰度值下,随着入射角度的增加,相位调制量逐渐减小;入射角度小于5°时相位调制曲线几乎重合,相同灰度值下相位调制量最大相位差为0.032λ。 The purely phase modulation characteristics of obliquely incident liquid crystal spatial light modulators were measured by Zygo interferometer. The pure phase modulation mathematical model of oblique-incidence liquid crystal spatial light modulator was established. The influence of oblique incidence angle on the phase modulation characteristics was studied. The measurement system based on Zygo interferometer was built. The phase modulation characteristics under different incident angles measuring. The results show that the phase modulation increases linearly at different incident angles, and the larger the incident angle is, the smaller the slope of the phase modulation increases. With the same gray value, the phase modulation gradually decreases with the incident angle increasing. When the angle is less than 5 °, the phase modulation curves almost coincide, and the maximum phase difference of the phase modulation under the same gray value is 0.032λ.