本文对圆形平面镜体采用背部开口式和背部平板封闭式两种轻量化结构在轻量化率相同的 情况下，作了多种结构参数的分析计算，对比了两种结构的自重镜面变形量，计算中发现背部封闭式结 构的参数变化对自重变形量的影响远小于背部开口式结构，因此在结构设计中可利用这一优点进一步 提高轻量化率。

An analysis is made on the influence to gravitational mirror surface deformation caused by the two lightweighting structurs having respectively a back-opened and back-closed round mirror body. Results of analysis show that the influence on back-closed lightweighting structures is much smaller than that of the back-opened case. This advantage can be utilized to further reduce the weight of mirror’s body.