The authors analyse the influence of reference sphere on the test accuracy of Ritchey–Common method during testing of flat mirror surface. A simulation model is established to simulate the influence of different radii of curvature of reference sphere on system wavefront. Then, the difference between the flat mirror surface result with reference sphere surface error to the actual flat mirror surface is examined by this model. The test accuracy of flat mirror result can be effectively improved by eliminating the influence of the surface error of reference sphere. When the surface accuracy of the reference sphere is better than 0.01 λ, the influence on RMS test accuracy is within 0.01 λ. R–C test path is built to test a 100 mm-diameter flat mirror surface, and its results are compared with those of the flat mirror surface without surface error of reference sphere and with the test result of the interferometer. When the surface accuracy of the actual used area of reference sphere is better than 0.01 λ, the effect on flat mirror RMS accuracy is within 0.01 λ. The RMS test accuracy can reach 0.01 λ, when the surface error of reference sphere is retained. The experiment verifies the correctness of the simulation results and guarantees the improvement in the test accuracy of R–C method.

中文翻译：

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参考球对Ritchey-Common方法测试精度的影响

作者分析了平面镜面测试时参考球面对Ritchey-Common方法测试精度的影响。建立仿真模型，模拟不同参考球曲率半径对系统波前的影响。然后，通过该模型检查带有参考球表面误差的平面镜表面结果与实际平面镜表面之间的差异。通过消除参考球面误差的影响，可以有效提高平面镜结果的测试精度。当参考球面形精度优于0.01λ时，对RMS测试精度的影响在0.01λ以内。搭建R-C测试路径，对直径100 mm的平面镜面进行测试，并将其结果与无参考球表面误差的平面镜面的测试结果以及干涉仪的测试结果进行比较。当参考球实际使用区域的面型精度优于0.01λ时，对平面镜RMS精度的影响在0.01λ以内。在保留参考球面形误差的情况下，RMS测试精度可达0.01λ 。实验验证了仿真结果的正确性，保证了R-C方法测试精度的提高。