大口径非球面的高精度检测中,补偿元件的质量对检测结果有直接影响。针对大口径抛物面计算全息板(CGH)因其空间频率高,误差控制难度大的问题,通过一个具体的设计,分析了加工过程中定位误差引起的光场畸变。为了减小误差的影响,采用双CGH光路进行非球面检测,具体分析了双补偿器结构非工作级次衍射光的分离情况,以及定位误差带来的光场畸变。结果显示：双CGH结构的最大空间频率远小于单片结构,其定位误差带来的光场畸变的RMSE值是相同条件下单片结构的0.65倍。这表明在补偿检测大口径非球面时,采用双CGH补偿元件,在满足设计要求的同时能很好的抑制其加工误差带来的影响。

In the high precision testing of large aperture aspheric surface, the quality of compensation devices has a direct influence on the result. For the large aperture paraboloid CGH due to its high spatial frequency, the error control is difficult. Through a specific design, the optical field distortion caused by the positioning error during machining is analyzed. In order to reduce the influence of error, the aspherical surface testing is performed by using the double CGH optical path. The separation of the non-operating order diffracted rays of the double compensator and the optical field distortion caused by the positioning error are analyzed. The results show that the maximum spatial frequency of the double CGH is much smaller than that of the monolithic structure, and the RMSE value of the optical field distortion caused by the positioning error is 0. 65 times that of the monolithic structure under the same conditions. It shows that when compensating for testing large aperture aspheric, double compensation CGH element, while meeting the design requirements can well suppress the influence of error caused by the processing.