Distributing aspheric surfaces drings down cost

Distributed and mild aspheric surfaces, and subaberture-stitching interferometry combine to form a cost effective approach to fabricating aspheric optics. Aspheric subaberture-stitching interferometry is used to measure the surface figures of aspheres such as ellipsoid (conic), which has a 100 mm aperture diameter, a base radius of 226 mm, and approximately 12 μm of aspheric departure. Subaberture-stitching interferometry allows small reference flats to provide complete tests of larger optical flats, or large-clear-aperture parabolas in double-pass autocol-limiting mode. A computer controlled stitching interferometer, commercialized for testing spherical parts, uses algorithms that exploit the apparent redundancy in the multiple measurements. This fully automated system can actually yield higher accuracy than the conventional full-aperture tests.