Low Cost Optical Finishing of Transparent Ceramics

"Refractive index matching glass coatings have been successfully applied to rough-ground sapphire blanks, providing a very-low-cost method for optical finishing. In Phase I, MSI is optimizing the application and polishing of index-matching glass coatingsand replicating optically-smooth surfaces using polished mandrels. The optical properties (in-line transmittance and image resolution) of resulting windows have been measured. A number of very promising glass-coated sapphire samples have been produced,demonstrating the feasibility of MSI's approach. These samples have in-line transmittance up to 88% and image resolution less than 1 mrad, exceeding the optical goals established for Phase II. In Phase II, MSI will scale-up the most successful low-costoptical finishing processes to 12 x 14 inch windows while maintaining the optical quality goals of the program. In order to produce and deliver 12 x 14 inch windows, it may be necessary to take advantage of MSI's sapphire edge bonding technology, whichwas developed previously under separate funding. Commercialization of the low cost finishing technology will be facilitated through MSI's on-going business relationships with BF Goodrich (formerly Raytheon Optical Systems - Danbury CT), RaytheonElectronic Systems (Lexington, MA), and as a result of interest expressed by the US Secret Service."