TECHNOLOGY AREAS: Air Platform, Materials/Processes, Sensors, Weapons

ACQUISITION PROGRAM: N-UCAS, Joint Strike Fighter

The technology within this topic is restricted under the International Traffic in Arms Regulation (ITAR), which controls the export and import of defense-related material and services. Offerors must disclose any proposed use of foreign nationals, their country of origin, and what tasks each would accomplish in the statement of work in accordance with section 3.5.b.(7) of the solicitation.

OBJECTIVE: Create techniques for grinding, polishing, and measuring aspheric, corrective infrared-transmitting optics for use with conformal windows and aerodynamic domes. Corrector elements might not have rotational symmetry.

DESCRIPTION: Future air vehicles will benefit from sensor windows that conform to the shape of the airframe. Conformal and aerodynamic shapes have the potential to reduce drag, increase the field of regard, and decrease signature. One possible scheme for transmissive corrective optics to go with an aerodynamically shaped dome includes a torroidal corrector element. Windows that conform to the shape of a fuselage might not have any elements of symmetry and could require optical correctors without any elements of symmetry. It is envisioned that future domes and windows could require corrective optics with diameters ranging from 100 to 300 mm.

Key technical challenges are to create methods to grind, polish, and measure precision surfaces with arbitrary shapes. There are no established methods in the optics industry to produce such shapes today. The contractor will need to develop new methods of deterministic grinding and polishing to achieve the required shapes with the required precision. The geometric form of a finished window must be precise to a fraction of an optical wavelength, typically on the order of 0.1 micrometer (or less). Ingenuity will be required to apply interferometry to measure conformal shapes with large departures from a spherical surface. Measurements must be fed back to a deterministic polishing process capable of bringing the optic to its required final form.

Proposals will likely be awarded in the areas of machining and metrology and these efforts will need to work together to complete Phase II. It is envisioned that this project will proceed in steps to develop applicable techniques first on inexpensive material such as glass or fused silica. Later, optics will be made from infrared-transmitting materials that could include zinc sulfide, zinc selenide, chalcogenide glasses, and spinel. Spinel will be particularly challenging because it is much harder than the other candidate materials.

PHASE I: Demonstrate techniques of grinding, polishing, and measuring a shape to be selected by the contractor. A material such as glass or fused silica with dimensions on the order of 50 x 50 mm would be suitable for this demonstration. A goal for optical figure is 0.1 wavelength root-mean-square deviation at 633 nm over a 50 mm diameter. Plan a clear path to scale the approach to larger sizes and infrared-transparent materials in Phase II.

PHASE II: Demonstrate grinding, polishing and metrology of toroidal corrector elements and other shapes selected by mutual agreement with the Government. Steps should lead from glass or fused silica to infrared-transparent materials. Steps should lead up in size to dimensions on the order of 200 x 200 mm. The final optical figure should be within 0.1 wavelength root-mean-square deviation at 633 nm over the full clear aperture of the part.

PHASE III: Develop a commercial process capable of making corrective optics for conformal windows with arbitrary shapes and optical figure similar to that of Phase II, but with areas on the order of 750 x 750 mm.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: Conformal windows with corrective optics could be used for synthetic vision systems on commercial aircraft. These windows could increase the pilot�s field of regard and might be used in locations that would not be suitable for flat windows.

REFERENCES:
1. P.H. Marushin, J. M. Sasian, T. Y. Lin, J. E. Greivenkamp, S. A. Lerner, B. Robinson, J. Askinazi, "Demonstration of a Conformal Window Imaging System: Design, Fabrication, and Testing," Proc. SPIE 2001, 4375, 154.

2. J. P. Schaefer, R. A. Eichholtz, and F. Sulzbach, "Fabrication Challenges Associated with Conformal Optics, Proc. SPIE 2001, 4375, 128.

3. J. E. Greivenkamp and R. O. Gappinger, "Design of a Nonnull Interferometer for Aspheric Wave Fronts," Appl. Opt. 2004, 43, 5143.

KEYWORDS: optical fabrication; metrology; optical finishing; conformal window; aerodynamic dome; infrared imager

TPOC: (760)939-1649
2nd TPOC: (760)939-1629

** TOPIC AUTHOR (TPOC) **

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