Study On The Computer-Aided Alignment Of Three-Mirror Optical System

As a result of the development of the complex optical system, the technology of the computer-aided alignment attract the people's interests. The paper includes that the development background, the history and current development conditions of the computer-aided alignment technology, and makes a conclusion about its optical testing means and its mathematical optimizing methods, and it is important and necessary of studying the computer-aided alignment of the complex optical system. This paper mainly presents the study of computer-aided alignment about a large aperture, long focal length, wide field, off-axis aspherical optical system. Based on the ideas that linearity instead of non-linearity and difference quotient instead of differential quotient, and establish the mathematical model on the computer-aided alignment. This mode is composed of the characteristics of the optical system, wavefront difference of its exit pupil and its misalignment of the misaligned optical system. Obtaining the practice value of parameter in this model is studied. The optical system could determine the unique sensitivity matrix and it could be calculated by the optical design software. Analyzing the relations between the Zernike polynomials coefficient and the wavefront difference and obtaining the Seidel wavefront error expressed by Zernike coefficient using autocollimation interforerence methods. Accomplished the study on the reserve optimization algorithm of computer-aided alignment. By means of the damp least square method and singular value decomposition method, the misalignment of optical system could be calculated. The first method make equations convergence quickly and the latter have a low demand for the start point, and combining two methods together would obtain misalignmentquickly and accurately. Then analyze the wavefront error data and explain the inputting cause of the damp factor. This algorithm could calculate better than famous optical design software CODE V. Accomplished the alignment calculation about three three-mirror optical system and established three difference alignment methods. The first method is the Condition Number of Sensitivity Matrix Method, it can decrease the dimension of the sensitivity matrix and decrease the degree of difficulty of solution; the secondary method is Gradual Aberration Optimization Method, it can directly remove the main aberration in the pupil gradually; the third method is Grouping Compensator Method, it benefits the aligned equipment high efficiency. Using Gradual Aberration optimization Method, a 6m focal length, 600mm aperture off-axis aspherical optical system is successfully aligned. Finally, the results of 0?field wavefront error of 0.094 waves RMS , +0.7= field of 0.106 waves RMS and -0.7c field of 0.125 waves RMS at A =632.8nm are obtained.