弯月薄镜在侧向均匀承重和弯月薄镜在采用侧向均匀承重和等间距竖直推拉侧向支撑方式时, 等间距竖直推拉侧向支撑方式时, 会产生明显的弯曲变形问题。为消除附加弯矩带来的镜面变形, 本文分析了弯月薄镜的结构特点, 提出了适用于弯月薄镜的等角间距推—拉—剪切和不等角间距推—拉—剪切两种侧向支撑方式。通过在侧向支撑上增加轴向剪切平衡作用力分量, 推导了在上述两种侧向支撑方式下各向作用力分量的表达式。针对1.23 m弯月薄镜, 优化出切向分量最佳比率β为0.75。对16点等间距侧向支撑增加轴向剪切分量后, 镜面变形RMS值由1259.1 nm减小到3.4 nm, 无需轴向主动校正即可获得较好的支撑面形。不等角间距侧向支撑方式则解决了等间距侧向支撑方式中各个侧向支撑点的作用力大小差异较大的问题, 结合弯月薄镜轴向支撑的主动校正能力, 在最大校正力仅为–1.01 N的主动校正后, 16点不等间距侧向支撑实现了镜面变形RMS为4.6 nm的支撑效果。

Thin meniscus mirrors with a lateral support in either equal weight vertical support or equal-angle vertical push-pull always generate bending aberrations badly. To eliminate the bending deformations, this paper analyzes the structure characteristics of the thin meniscus mirrors and proposes two kinds of lateral support models including equal-angle push-pull shear and unequal-angle push-pull shear for the thin meniscus mirrors. By increasing the axial forces on lateral supports to balance the force components, the tangential force, radial force and axial force of the lateral support are expressed for both lateral support modes. The parameters of a 1.23 m thin meniscus mirror are optimized, and the results show that the parameter β(determines the contribution of tangential forces to weight support) of a 16-point lateral support system is 0.75. After applying axial shear component to the 16-point equal-angle push-pull lateral support, the mirror deformation( RMS) is reduced from 1259.1 nm to 3.4 nm, showing a better support surface. The equal-angle push-pull shear lateral support mode is successful in reducing deformation without active correction, but it has a major disadvantage in a great force difference between lateral support points. Considering uniformity and practicality for lateral support mechanism, the 16-point unequal-angle push-pull shear lateral support mode is used to achieve 4.6 nm deformation(RMS) with axial active correcting by the maximum active force of only –1.01 N.