Optimization of Converging-Beam Grating Monochromators*

Design principles for the optimization of a version of the Monk–Gillieson grating monochromator are developed. Third-order aberrations for coma and astigmatism are both compensated for one wavelength, which can be chosen as wanted. The general relations for the orientations of the imaging mirror and the plane grating, with respect to each other and to the light-bundle axis for correct compensation of imaging errors, are developed. Expressions are given for the residual aberrations at other than the compensated wavelength. The results are applied to a typical mirror–grating combination.