The threemirror anastigmatic system includes two aspherical concave mirrors and a spherical convex mirror.

所设计的三反射镜消像散系统包括两个非球面凹反射镜和一个凸球面反射镜。

It is also shown that only when the gratings are cylinder or plane ones, the second order sagittal anastigmatic circular field and meridional non defocus flat field spectral images can be formed.

还指出仅当柱面或平面光栅时，才能形成二阶子午无离焦平场和弧矢无象散圆场谱面。