研制大口径望远镜系统,通常采用组合口径反射镜来代替单体反射镜.组合口径反射镜的方案相比于传统方案减小了加工、运输等各方面的困难,同时它也会引入分块镜的曲率半径误差.为更好地了解组合口径反射镜曲率半径误差对光学性能的影响,文章以整体口径为6.6m、曲率半径为21.34m的由18块六边形分块镜拼接而成的反射镜为例,对组合口径反射镜曲率半径误差进行分析.首先建立组合口径反射镜模型,通过计算求得反射镜的波像差与斯特列尔比,最终确定反射镜曲率半径误差的合理变化范围.结果表明,曲率半径误差对不同位置分块镜的波像差影响不同,去除位置因素后,各分块镜对反射镜波像差的影响相同.文章所设计的反射镜,如果各分块镜之间的曲率半径误差应小于±0.14mm,则满足斯特列尔比大于0.8且最大波像差小于λ/4.文章对组合口径反射镜的设计、加工和装调等有参考价值.%There are big advantages using segmented mirror instead of monoliphic mirror to build large aperture telescope. There are less difficulties in fabrication, transportation and adjustment using segmented mirror comparing with the traditional scheme, in the meanwhile, the error of curvature radius is generated. In this paper, the error of curvature radius is analyzed on the basis of a 18 segmented hexagonal mirrors with the monolithic aperture of 6.6 meters and the curvature radius of 21.34 meters to better understand the impact of the curvature radius error of segmented mirror on optical system. First of all, the model of segmented mirror is built, then the wave aberration and Strehl Ratio of mirror are analyzed, at last the reasonable error range of curvature radius of mirror is determined. The results show that the curvature radius has various impact on wave aberration of segmented mirror in different position, when the factor of position is removed, the impacts are the same. For the mirror designed in this article, if the curvature radius error of segmented mirror is within ±0.14mm , then the mirror will satisfy that Strehl Ratio is more than 0.8 and the maximum wave aberration is less thanλ/4. This paper can offer some important reference for the design, process and adjustment of the segmented mirrors.
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