1. 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。
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2. 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.
