Study On The Structure Design And Test For Sub-aperture Stitching Optical System

Since last century80years, the development of space technology is amazing. At the same time with research on space, the demand of space technology, especially space optical technology is updated.To adapt requirements of modern astronomical observation and war, the next generation space telescope will need larger aperture, lower weight, higher imaging quality and flexibility compared with traditional single primary mirror system.The angular resolution of traditional optical imaging system is limited by wavelength and aperture. Under condition of fixed working wavelength, the only method of increasing angular resolution is to enlarge system aperture. While the fabrication of large and super large aperture system is limited by material, fabricating technology, cost and loading ability. Based on the above factors, the available technology could not solve the contradiction. The optical system could be fabricated and aligned separately applying sub-aperture stitching technology. Consequently, the system aperture could be enlarged.The key technology in the design, fabricating, alignment and testing of sub-aperture stitching principle prototype is deeply researched. The research work is as following.The imaging character of sub-aperture stitching system is represented. And the visual and CCD imaging resolution are calculated theoretically.The alignment tolerance of sub-aperture stitching system is analyzed with nodal point concept of dynamic optics. It is shown from analysis that the maximum permitted lateral displacement of edge sub-aperture is0.003mm, the longitudinal displacement tolerance is0.02mm, and the tilted tolerance is1.15μrad. The conclusion is that the permitted tolerance of edge sub-aperture is small. The alignment difficulty is very large. And this is also difficult point of sub-aperture stitching system.The supporting structure of sub-aperture stitching system is designed. The design works is composed of the supporting structure of central mirror, the supporting and adjust structure of edge mirror, the supporting structure of secondary mirror and the supporting structure of compensation lens. The stitching primary mirror is also analyzed with finite element method.The system stray light is simulated and analyzed. Based on this work, the eliminating stray light stop is designed reasonably. With the stray light analysis result, the structure of the whole system is completed.Based on analysis of optical system character, the testing and alignment project is proposed. It is referenced with central primary mirror to adjust the edge sub-aperture. The concentricity of edge sub-aperture with central primary mirror is adjusted with auto-collimating optical element and rotatable guide. The fabricating difficulty of large auto-collimating plane mirror in testing of sub-aperture stitching system is solved.Based on the system analysis, the element fabricating and whole system alignment of sub-aperture stitching principle prototype is completed. And the performance of prototype is tested. It is shown from the testing result that it meets the system requirements excluding the visual resolution, which is far from the theoretical analysis.According to the problems from stray light eliminating, system residual stress in the testing and alignment process, the corresponding improved method are given in detail. It provides strong foundation for further development of sub-aperture stitching system.