Patent ID: 7728987

Claim:
A method of manufacturing an optical element having an optical surface of an aspherical target shape having an axis of rotational symmetry, the method comprising: directing a beam of measuring light onto the optical surface using an interferometer optics, the interferometer optics comprising at least one substrate carrying a hologram, wherein at least a portion of the beam of measuring light traverses the at least one substrate carrying the hologram, wherein the portion traversing the substrate illuminates only a portion of the optical surface, and wherein an area of the illuminated portion on the optical surface is less than about 80% of a total area of the optical surface; positioning the optical surface at plural rotational positions about an axis of rotation which substantially coincides with the axis of rotational symmetry of the target shape of the optical surface, and performing at least one first interferometric measurement at each of the plural rotational positions of the optical element by superimposing reference light with measuring light having interacted with the illuminated portion on the optical surface; determining deviations of the optical surface from its target shape based on the first interferometric measurements taken at the plural rotational positions of the optical element; and processing the optical surface of the optical element based on the determined deviations, wherein plural substrates, each carrying a hologram, are disposed adjacent to each other such that each substrate is traversed by a separate portion of the beam of measuring light.