| With the development of optical manufacturing technology, three reflective mirror optical systems with large field, high resolution, and long focal length is more and more widely used in astronomical optics, space optics, and ground based space target detection and identification and other fields. High-precision aspheric mirror processing is one of key technologies of large field off-axis optical system. How to objectively and accurately evaluate the aspheric surface is the basis of application of large-diameter high-precision aspheric mirror.Currently, method of compensation test is commonly used in engineering to test the high-precision aspheric mirror. But material of compensator, processing and assembling error, and the adjustment of testing light path in the process of compensation testing can lead negative impact to the test results of the system, introducing additional aberrations. These errors will be treated as surface error and corrected in the polishing process if they are not eliminated. This will lead incorrect error input when correcting the aspheric surface.This article is based on a coaxial three reflective system, aimed at solving the practical needs of engineering. This article mainly carries out research in the following aspects:1. According to the features of parameter and processing precision requirement of the concave parabolic primary mirror in the coaxial three reflective system, several 2. testing scheme are designed and their feasibility are analyzed. Finally the zero compensation testing method is applied, and completed the design of the Offner compensator. Primary mirror of the TMC system is tested by the designed compensator, and the testing result meets the required precision.3. Analyzed the error sources that influence the aspheric surface compensation testing. The analyze is performed from several aspects such as the design, processing and assembling of aspheric surface compensation testing system and adjustment of testing light path. Finally quantitative expressions of the influence of every error source made to the testing results are given.4. Analyzed the feature of every error source that influences the aspheric surface compensation testing result. The aspheric surface compensation testing error is boiled down to three categories: circular symmetry error, non-circular symmetry error and the adjustment error of testing light path. For characteristics of these error sources, numbers of error correcting methods are applied to correct the various errors, and the consistency and correctness are verified by experiments.5. Derived the expression of aspheric surface parameter. Proved that there’s unique solution for aspheric surface parameter when best wave front is obtained. Analyzed the accuracy of solving the aspheric surface parameter using inversion method, and the consistency and correctness are verified by experiments.In summary, this article solves the testing result’s accuracy problem of aspheric surface zero compensation testing method, and the hard-to-test problem of large diameter aspheric parabolic approximation parameter. This is bound to improve our ability to test high-precision aspheric surface, and there’s great significance to improving the competitiveness of optical information industry and national defense industry of our country. |
