The properties of a plane grating when it is illuminated by a convergent or divergent wave front are investigated. The investigation shows that the image principally suffers an unsymmetric aberration of coma type in the direction of dispersion. Remedies have been indicated to correct this aberration.
M. V. R. K. MURTY, "Use of Convergent and Divergent Illumination with Plane Gratings," J. Opt. Soc. Am. 52, 768-773 (1962)