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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=0.6328μm)。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 further improve the detection accuracy of Ritchey-Common method, the influence of Ritchey’s angle accuracy on the overall test results was analyzed. The simulation results show that the best Ritchey angle test range is between 20 ° and 50 °, and the accuracy of surface error detection can reach 0.01λ (λ = 0.6328μm). When the Ritchey angle error is controlled within ± 1 °, the residual of the fitting result and the original surface shape is reduced to 0.0007λ, which can meet the test requirements. Aiming at the problem of Ritchey angle measurement error, the Ritchey angle is calculated by measuring the image compression ratio of the pupil plane of the system. The calculation error of this method can be controlled within 0.2 °. In the experiment, three angles are selected for detection. When the data is processed, the measured data are solved in two or two combinations. The peak-to-valley (PV) values of the residuals of the 29.6 ° & 47.8 ° combination fit and the Zygo interferometer results were 0.068λ and the root mean square (RMS) value was 0.0105λ, proving the choice of Ritchey’s angle and its calculation The accuracy of the overall accuracy of the test has a certain impact.