Study On Technology Forlarge Optic Flat Mirrortesting

With the rapid development of science and technology, large-aperture opticalsystems are more widely used in space optics, astronomy optics and other fields.Large optical flats are often used as reference surfaces in autocollimation optic tests.Thus, a high-quality surface and a suitable and highly precise test method isnecessary. Currently the largest commercial digital interferometer of1meteraperture is not available to cover the large mirror which diameter is more than1mduring tests. This paper analyzes some common method which widely used in largeaperture flat mirror test, and select Ritchey-Common test method as the maincontent.According to the theory of Ritchey-Common test, this paper analyzes therelationship between the system wavefront and flat mirror surface. To solve thedifficulties in the Ritchey-Common test that a single measurement could not obtainthe test flat mirror surface, this paper change the main optical path to derive thesurface from two different test angles. And we utilize the relationship betweensystem pupil coordinate and flat mirror coordinate to derive the surface. The detailsand accuracy of the data processing method is well presented. The accuracy canreach to0.01(=0.6328μm), a more actual flat surface error could be obtain forthe alignment error of optical path separated.Compared the methods of using the influence matrix with our method of using relationship between system pupil coordinate and flat mirror coordinate to figure outthe flat surface by simulation.The result shows that our method is more accuracy andsuitable for Ritchey-Common test. Asuitable range of the Ritchey angle is identified,and its error allowance is determined by simulation. The ratio of image size to thepupil plane is used to calculate the Ritchey angle in test, the accuracy of this methodfor calculating is high enough. The distance between the lens focus and the flatmirror center is analyzed. We test a flat mirror with a small diameter in threedifferent Ritchey angles. The results of the Ritchey-Common test and the directmeasurement with Zygo are very close; the experimental results confirm that thisRitchey-Common method is effective and accurate.And this provided analysis foractual tests.This paper also introduces the composition and principle of the scanningpentaprism test system which is very important for large aperture optical test. Themethod could be used to test large flat mirror which diameter is larger than1m.This paper focuses on analyzing scanning accuracy of the pentaprism, andprogramming software that used to calculate the manufacturing errors of thepentaprism and the angle error when moving in three-dimensional direction. Theresults are used in the subsequent data processing. We also analyze the relationshipbetween the scan lines and the primary aberrations, and select the polar coordinatescan sampling method for testing which is more accurate and efficiency.We build the Ritchey-Common test path for a1.5m flat mirror. A well spherewith the diameter of1.8m and the radius of curvature is15m was used as areference. We derive the surface from two different test angles. In the results, PV andRMS can reach0.391(=0.6328μm) and0.0181(=0.6328μm) respectively.The test of1.5m flat mirror is finished by Ritchey-Common method. Theexperimental results confirm that this Ritchey-Common test method is effective andaccurate.