Patent ID: 7342667

Claim:
A method of processing an optical element having a spherical surface, the method using light beams of a spherical beam type, the spherical beam type including beams having one of substantially spherical wave fronts and substantially plane wave fronts, the method comprising: providing a first interferometer apparatus having an interferometer optics, wherein the interferometer optics comprises an aspherical lens configured to transform a beam of a first spherical beam type into a beam of a second spherical beam type, the aspherical lens having at least one aspherical surface; arranging the optical element in a beam path of an incident beam of a third spherical type provided by the interferometer optics; interferometrically taking a first measurement of first wave fronts generated by reflecting the incident beam from the spherical surface of the optical element; and determining first deviations of the spherical surface of the optical element from a target shape thereof in dependence on the first measurement; wherein the method further comprises: arranging the aspherical lens in a beam path of a measuring beam provided by a beam source of a second interferometer apparatus such that the measuring beam passes the aspherical lens and is reflected from a reflecting surface, wherein the measuring beam, between the aspherical surface and the reflecting surface, is one of the first spherical type and the second spherical type; interferometrically taking a second measurement of second wave fronts generated by reflecting the measuring beam from the reflecting surface; and determining second deviations of the at least one aspherical surface of the aspherical lens from a target shape thereof in dependence on the second measurement.