Analysis of the changes in efficiency across the ruled area of a concave diffraction grating

Measurements and calculations have been made to investigate the effects due to the change in groove orientation on efficiencies of gratings ruled on a spherical surface. Typical efficiency maps across the surface are given for various angles of incidence and wavelengths in the VUV and UV regions. Computations based on electromagnetic theory show a good agreement with the experimental data over the 150-2500-A wavelength range. A simple explanation is given to interpret and predict the shape of efficiency maps obtained from both theory and experiments.