The change in blaze wavelength as a function of position on a blazed concave diffraction grating surface is discussed. An experimental study of ruled and interferometric blazed concave gratings showed that the change in blaze across the grating surface is much less for an interferometric grating than for a ruled grating. Thus interferometric gratings can be expected to have a more uniform distribution of efficiency across their surfaces.
M. C. Hutley and W. R. Hunter, "Variation of blaze of concave diffraction gratings," Appl. Opt. 20, 245-250 (1981)