为进一步提高Ritchey-Common法的检测精度，分析了实验中Ritchey角精度对整体检测结果的影响。通过仿真模拟，分析并确定出最佳Ritchey角测试范围在20°~50°之间，此时面形误差检测结果精度可达0.01λ（λ=0.6328 μm）。仿真过程中模拟Ritchey角存在误差时对检测结果的影响，当Ritchey角误差控制在±1°时，拟合结果与原始面形的残差降至0.0007λ，能够满足测试要求。针对Ritchey角测量存在误差的问题，利用测得系统光瞳面的图像压缩比例来计算Ritchey角大小，此方法的计算误差可控制在0.2°以内。实验中选择3个角度来检测，在数据处理时将测得数据两两组合进行解算。29.6° & 47.8°组合拟合结果与Zygo干涉仪直接检测结果的残差的峰谷(PV)值为0.068λ、均方根(RMS)值为0.0105λ，证明Ritchey角的选择及其计算精度对检测整体精度具有一定影响。

In order to improve the accuracy of Ritchey-Common (RC) method, the effect of accuracy of Ritchey angle on test results is mainly discussed. By means of simulations, the measured accuracy of surface error can reach 0.01λ(λ=0.6328 μm) when Ritchey angle′s range is optimized between 20°~50°. The error of Ritchey angle is simulated to analyze the influence on measured result. When the error of Ritchey angle is controlled within ±1°, the accuracy of residual error between fitting results and original surface can be decreased to 0.0007λ and meets the measured requirement. To avoid the measurement error of Ritchey angle, the ratio of image size on pupil plane is used to calculate the Ritchey angle, and this method′s accuracy can reach to 0.2°. Three Ritchey angles are chosen in the experiment and combined with each two of them. For the residual error between Zygo measurement and group of 29.6° & 47.8° measurement, the peak valley (PV) is 0.068λ and the root mean square (RMS) value is 0.0105λ. The results demonstrate that the choice of Ritchey angle and its calculation accuracy are important to RC method.