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 pure phase modulation characteristics of a liquid crystal spatial light modulator are measured at oblique incidence using Zygo interferometer. The establishment of a mathematical model of pure phase modulation of liquid crystal spatial light modulator at oblique incidence, the effects of oblique incident angle of the phase modulation characteristics, structures based Zygo interferometer measurement system, and phase modulation characteristics under various incident angles are measured. The measurement results show that, at various incident angles, phase modulation increases approximately linearly, and the larger the incident angle, the smaller the increasing slope. With the same gray scale value the phase modulation amount decreases when the incident angle increases. When the incident angle is less than 5°, phase modulation curves almost coincide, and the maximum phase difference of the phase modulation amount is 0.032l with the same grayscale value.