A method of manufacturing an optical element having an optical surface of a non-rotationally symmetric shape is described. Measuring light is generated using an interferometer optics, wherein the interferometer optics has at least one diffractive component having a grating. The optical surface is positioned at a first position relative to the diffractive component, wherein first measuring light diffracted at the diffractive component is incident on the optical surface at plural locations thereof, and at least one first interference pattern generated from first measuring light reflected from the optical surface is detected. The optical surface is positioned at a second position relative to the at least one diffractive component, wherein second measuring light diffracted at the diffractive component is incident on the optical surface at plural locations thereof, and at least one second interference pattern generated from second measuring light reflected from the optical surface is detected.