Patent ID: 6943897

Claim:
A method for fabricating and inspecting an optical element, comprising the steps of furnishing a light-transparent blank having an element axis; thereafter forming a spherical-segment surface in the light-transparent blank at a first end thereof, wherein the spherical-segment surface has a spherical-segment center on the element axis; forming a trial parabolic surface in a lateral surface of the light-transparent blank spaced apart from the element axis, wherein the trial parabolic surface has a trial-surface parabolic focus substantially coincident with the spherical-segment center; and thereafter inspecting the trial parabolic surface by directing a source light beam from a light source through the light-transparent blank parallel to the element axis and against the trial parabolic surface, whereupon a reflected light beam reflects back from the spherical-segment surface substantially parallel to the source light beam but oppositely directed to the source light beam, and optically interfering the reflected light beam with the source light beam to produce an interference pattern.