Optical Design Of Four-mirror Systems With Ultra-large Aperture

Optical systems with ultra-large aperture and ultra-long effective focal length haveimportant applications in space remote sensing and astronomy. The existing systemsmostly use the aspherical mirror as the primary which is hard to make large aperture due tothe difficulty of fabricate and assemble. So how to facilitate the fabrications of largeaperture is need to be solved.In this paper four-mirror systems with huge aperture and long focal length isinvestigated and designed. The spherical mirror and parabolic mirror are used as theprimary to reduce the difficulties of fabrication. Firstly, the method to determine its initialstructure is reported. A strong aspheric quaternary with smaller aperture is placed close tothe exiting pupil to correct residual aberrations. Secondly, the initial structure parametersof the optical system are obtained with P-W method, then through the derivation ofprimary aberration formulas, the aberration property are analyzed and discussed. Thirdly,as examples, several four-mirror systems with 10m aperture and 100m focal-length areoptimized by the ZEMAX optical design software and given in detail. They have somemerits such as ultra-large aperture, wide field, perfect image quality, and no secondobstruction. Finally, tolerances are assigned to the optical and mechanical component withthe goal of meeting the optical performance and minimizing the cost.