| With the development of the optical technology, large flats with high precision are widely used in space optics and high-power laser technology. The manufacture of large flats demand testing method with high precision. Based on the project "Measurement of aΦ1.1m flat using Ritchey-Common method", the Ritchey-common testing method of large flat are studied.After studying the theory of the Ritchey-Common test, the calculation formula of the sag of the flat are derived; the relationship between Ritchey-Common angle, surface error and wave-front aberration is derived. A simulation experimental device is constructed by ZEMAX to determine the error in the measurement result due to the surface deformation of the flat, besides, a simulation is performed to determine how the measurement results be influenced by different Richey angles.AΦ75mm plane mirror is measured using Zygo interferometer in two angular positions. Both Ritchey-Common test and direct measurement results are presented. In comparison of the two methods, the Ritchey-Common test is in good agreement with the direct measurement. Surface error of theΦ1.1m flat is measured using 4D interferometer in two angular positions of 40°and52°. The surface error of the mirror is calculated using Ritchey-Common algorithm, PV is 0.237λ,RMS is 0.024λ.The result meets the processing requirements and represents the Richey-Common test is effective in the measurement of large flat. |
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