GEOMETRIC OPTICAL THEORY OF DIFFRACTION GRATINGS

The aberration theory of diffraction gratings has been investigated by means of geometric optics. No restrictions are imposed on the form of the grating surface, the pattern of the grooves in the grating surface, and the position of the object. Furthermore, the image plane is not limited to one normal to the principal ray. All of the terms up to the fourth order with respect to the pupil coordinates are taken into account in a series expansion of the light path function. The results give the focal positions, of the radius of curvature of the astigmatic image, the shape of this image, the optimum slant angles of the image plane, the resolution by geometric optics, and the condition for absence of comatic broadening.