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Manufacturing of Visibly Transparent Large Conformal Windows


Conformal electro-optic sensor windows are desirable for future air platforms as they maintain the shape of the aircraft moldline and allow for a large sensor angle of regard. Such windows may have little to no symmetry depending upon their location. Spinel is an excellent candidate window material as it is both durable and multi-spectral (ultraviolet through mid-wave infrared). Spinel is more erosion resistant than multispectral zinc sulfide, which is another logical candidate for a large conformal window. The objective for this project is to create methods to grind and polish freeform conformal sensor windows with dimensions up to 24x24 inches with a sag height of approximately 8 inches and an optical precision of 0.5 micron or better. It is expected that methods will be developed with glass or fused silica and that a full sized window will be made from glass or fused silica. It is also possible that a full sized spinel blank may be available from the government during this project. PHASE I: Demonstrate the feasibility of grinding and polishing a glass or fused silica conformal window with dimensions of 12x12 inches. The contractor shall propose a shape with a window sag height of approximately four inches and lacking rotational symmetry. The precise shape of the conformal window will be selected by mutual agreement with the government. The root-mean-square precision of the optical figure shall be 0.5 micron or less with a clear aperture extending within half an inch from the edge. PHASE II: Based on Phase I effort, scale up window fabrication with glass or fused silica to lateral dimensions of 24x24 inches with a sag of approximately eight inches. The shape shall be proposed by the contractor with mutual agreement from the government. A root-mean-square precision of the optical figure of 0.5 micron or less with a clear aperture extending within half an inch from the edge is desired. There is a possibility that a spinel blank will be made available by the government for Phase II. PHASE III: Implement commercial manufacturing capabilities for large conformal windows made of durable ceramics such as spinel. Manufacture an instrument for sale to optics manufacturers to make large, aggressively aspheric optics. Alternatively, provide a commercial service to manufacture such optics.

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