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Freeform Optics for Small Arms Fire Control

Description:

TECHNOLOGY AREA(S): Weapons 

OBJECTIVE: OBJECTIVE: Design, develop, prototype and demonstrate a selection of Freeform Optics that allow for the reduction of lens elements required to reproduce color-corrected imagery. Evolve the technology for manufacturability and survivability in a military environment. This technology will benefit Squad, Crew Served and Sniper fire control systems by reducing the size, weight and complexity of Fire Control devices and enablers. 

DESCRIPTION: The necessity for snipers, soldiers, and crew served weapons operators to rapidly and accurately detect targets on the battlefield is a capability that is of high interest to the department of defense, across all agencies. Traditional optics are radially symmetric while freeform optics can be non-radially symmetric. The increased flexibility of freeform optics allow for potentially revolutionary optical designs. Previously freeform optics were not really practical due to manufacturing limitations. Additive manufacturing technologies such as three dimensional printing are making an entire new generation of optical components and designs possible. For example, an Alvarez lens system is capable of providing a continuously variable focal length with a compact size. A Freeform optical element that is able to precisely focus light at different wavelengths will reduce the number of optical components required in a weapon mounted fire control sighting system, greatly reducing the size and weight of the system. The threshold wavelength range is 390nm to 700nm (Human Visible Spectrum). The objective wavelength range is from 390nm to 1600nm. The intent is for the contractor to determine what level of achromaticity is achievable across the spectrum of visible light using this technology. The Freeform lens design and manufacturability technology developed under this effort will result in cost and weight savings across all branches of the armed forces. The transition of this technology to industry will reduce the size, weight & complexity of optical systems by reducing the number of lenses required in nearly every precision optical system. 

PHASE I: Identify materials, methods and models for producing Freeform Optics, in particular solutions that use 3d printed polymeric materials, however, it is not the intent of the author to specify how the optics are to be fabricated. Optical properties shall be modeled, and performance quantified. Small-scale proof-of-concept samples shall be produced with identified materials and methods. Any software utilized and literature addressed shall be identified by the contractor. Contractor shall clearly state in the proposal and final report how the phenomenology provides the unique capability for achieving the design goals. Freeform optic design software will be used to define how a fielded small arms fire control system could benefit from a Freeform design. Efficiencies of at least 10% shall be demonstrated through modeling of the optical system design complexity (the number of optical elements), the size of the optical system, and the commensurate savings in weight shall all be described in the final report. 

PHASE II: Develop prototype Freeform optical units. Prototype shall be F/7 or faster, with a half field of view no less than 5 degrees. Prototype shall be optimized for a minimum of three (3) visible wavelengths (486nm, 587nm, 656nm). A variable magnification system based on Alvarez lenses or another freeform optic is of considerable interest. The contractor shall perform modeling and simulation that quantifies the optical performance of the prototype (Spot Diagrams [Both Monochromatic & Polychromatic], Ray Fans, MTF [Modulation Transfer Function], Distortion, and Field Curvature). A prototype shall be fabricated and delivered to the Government. Testing shall be conducted on the prototype to verify its actual performance versus modeled expectations. The Government will keep at least one prototype. Any software utilized and literature addressed shall be identified by the contractor. Contractor shall clearly state in the proposal and final report how the phenomenology provides the unique capability for achieving the design goals. Efficiencies of at least 20% shall be demonstrated through modeling of the optical system design complexity (the number of optical elements), the size of the optical system, and the commensurate savings in weight shall all be described in the final report. Technology Readiness Level (TRL): 3 

PHASE III: Optimize the physical properties for military applications. Prototype a rifle mounted fire control sight using this technology that demonstrates the benefits in size and weight over currently fielded systems. Replace conventional optics with the design in a sight that represents the optical performance of a fielded military small arms sighting system. Test and report the results of the optical metrology/performance and weight savings. Create a partnership with industry to commercialize the technology and improve the manufacturability. The prototype will be TRL 4 at the end of phase III. 

REFERENCES: 

1: Freeform: S. Barbero, J. Rubinstein, J. Opt 13 (2011) 125705

2:  A. Moehl et al., SPIE vol 10690, 1069017 (2018).

3:  https://phys.org/news/2017-08-freeform-optical-device-smaller-package.html#nRlv

4:  https://phys.org/news/2018-05-method-guesswork-lenses-freeform.html

5:  http://www.nature.com/articles/s41467-018-04186-9

6:  https://phys.org/news/2015-11-telescope-mirrors.html

7:  https://www.spiedigitallibrary.org/conference-proceedings-of-spie/10690/2313114/Ready-to-use-a-multi-focal-system-based-on-Alvarez/10.1117/12.2313114.full?SSO=1

KEYWORDS: Conformal Optics 

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