Spectral focusing characteristics of a grazing-incidence flat-field grating spectrometer

The spectral focusing characteristics of a grazing-incidence flat-field spectrometer with a spherical variable-line-spacing grating in the 5－40nm spectral range are presented. The spectrometer can be used for any object at a distance in the 50mm－infinity range from the grating apex with a diffracted spectrum sharply focused on an almost flat focal plane at a constant distance from the grating apex.