A method of gravity elimination in the testing process by using a highly lightweight mirror

摘要

As the caliber of a Spatial Optical Remote Sensor increases constantly, it is an inevitable trend to design a highly lightweight mirror. In the testing process of the mirror surface with a large caliber and higher lightweight level, the supportive distortion caused by gravity is a crucial factor that influences its testing precision. Aiming at this problem, we studied a testing method on the rail surface of the tested mirror that was detached from the gravity field. Deviations of the mirror wave surface were expressed by Zernike polynomial functions, so that wave surface data from different angles could be calculated by superposition. The optical axis vertical approach is adopted to test the wavefront of the aspherical mirror. By rotating the measured mirror, the surface shape data in different directions is tested. Through superposition calculation of the Zernike coefficients, the cumulative error of the test optical path is eliminated. In the same approach, the wavefront data of the surface of the reflecting mirror after rotating 180 degrees is measured . By using the finite element analysis, it is known that the deformation directions of the reflecting mirror in the two states are opposite caused by gravity during the test. And the orbital surface deformation data of the mirror can be obtained by calculation.