Рассмотрена возможность компенсации астигматизма в широком интервале длин волн в схемах нормального падения на основе сферической дифракционной решетки с переменным шагом. Рассчитаны две схемы изображающих спектрографов с габаритами около 1 и 5 m для диапазонов длин волн 820−1690

A high-resolution monochromator with a broad spectral range of 125 – 4200 Angstrem is designed for the measuring beamline for the projected synchrotron radiation source "SKIF" (Novosibirsk). The optical configuration of the monochromator comprises a grazing-incidence concave mirror, a plane VLS grating, and an exit slit. It is planned to use two replaceable VLS gratings with central line frequencies of 600 mm-1 and 150 mm-1 intended for subranges of 125 – 1000 Angstrem and 900 – 4200 Angstrem , respectively. Wavelength tuning in each of the two subranges is effected by only the rotation of the VLS-gratings. Due to the proper choice of p_1 VLS-grating coefficients, the focal distance varies only slightly over the entire spectral range, and the p_2 VLS-grating coefficients are used to suppress the aberrations of the mirror and the gratings. The resolving power of the configuration obtained by numerical ray tracing exceeds 1000 in the 125 – 1000 Angstrem range and 2000 in the 900 – 4200 Angstrem range.