Optical image development using parallel gratings - has plane of spherically concave diffraction gratings with similar line spacings and specified relative positions

摘要

The basic system of the optical image former uses two plane diffraction gratings (2,4) with rulings running in directions parallel to one another. The centre-lines of each grating (3,4) are also parallel. The angles (alpha 1, 2, beta 1,2) between the incident and diffracted rays for each grating follow simple trigonometrical relationship. Alternative systems use concave gratings, with spherical surfaces and similar line spacings. The distance between the central points of the gratings is close to the product of the radius of curvature of the grating and the cosine of the angle of incident radiation.