Advanced Metrology for Atypical Optical Surfaces

The objective for Phase II is to develop an automated subaperture stitching system capable of measuring strong aspheres. In particular, we aim to test aspheres with a thousand waves of aspheric departure (from best-fit sphere), to high accuracy, and withsufficient lateral resolution to measure mid-spatial frequencies. Furthermore, the system will be flexible - not relying on any special setup or null optics specific to any aspheric shape and capable of measuring a wide range of aperture sizes. Suchflexibility will make the system more cost-effective and reduce lead times, particularly for larger parts. This combination of dynamic range and flexibility is well beyond the current capability of commercially available equipment. A two-tiered approachwill be used: i.) establish stitching capability for aspheric interferometry and ii.) further develop metrology gauge to extend range if necessary. The Phase II work will: focus on figure metrology of individual surfaces, rather than composite opticalassemblies; concentrate on rotationally-symmetric surfaces and off-axis sections thereof, as well as cylinders and toroids; strive to reach nanometer-level accuracy (although measurement of larger parts and aspheric departures will entail trading someaccuracy); enable measurement resolution on the order of 1 millimeter or less. Developing a metrology tool for measuring atypical optical surfaces is important for many applications. Conformal domes and windows are immediately needed by the Department ofDefense for surveillance, target acquisition, and guidance systems. Additional applications include precision optics for consumer, scientific, and semiconductor products.