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Identification Friend or Foe (IFF) Panel with Dynamic Contrast at Long Wave Infrared (LWIR) Wavelengths

Description:

TECHNOLOGY AREA(S): Materials 

OBJECTIVE: To develop a panel comprised of pixels with variable emissivity at long-wave infrared (LWIR) wavelengths. The purpose of the panel is to form an Identification Friend or Foe (IFF) device utilizing LWIR communication. 

DESCRIPTION: The IFF panel, also known as a Combat Identification Panel (CIP), is a passive device mounted on allied military ground vehicles to distinguish them from enemy vehicles during engagements. CIPs were developed in the 1990’s to reduce friendly fire incidents by creating an easily identifiable infrared (IR) signature when viewed through a thermal sight. Originally made using metal slats spaced from the body of the vehicle to create a thermal separation, they were then coated with low-emissivity tape so as to appear cooler through thermal viewers. The CIPs are usually mounted on the sides and rear of the body and/or turret. With the broad proliferation of low-cost thermal sensors, the use of a standard high contrast, passive IFF/CIP on military vehicles increases the likelihood of an enemy sensor being able to discern a ground platform from the surrounding background. However, if the panel were dynamic, with adjustable contrast, it could be turned on or off depending on the mission profile, and it could be adjusted for various backgrounds. This could be achieved through a panel comprised of an array of segments with variable infrared contrast (variable emissivity), which could be used as an IFF /CIP device when viewed through LWIR imagers. A few methods of varying emissivity were investigated previously for thermal management of small spacecraft; here, electrochromic, electrostatic, and MEMs devices were explored.1 Variable emissivity has also been studied extensively in electrochromic and thermochromic material systems, with reasonable dynamic range; however, devices tend to suffer performance and/or degradation issues dependent upon the material system of choice.2 Thus, a more robust method of providing the dynamic IR contrast would need to be investigated, or performance and degradation issues would need to be addressed for electrochromic and thermochromic material systems in order to develop an acceptable IFF/CIP. 

PHASE I: Development of LWIR contrast changing technology suitable for use on military ground vehicles. Fabrication of at least 4 infrared devices (comprising an area of at least 6” by 6”) to be characterized by the Government. Characterization will include outdoor performance experiments and indoor lifetime evaluation. The devices must maintain their hue while maintaining a visible reflectivity within 25% during infrared switching (reflectivity integrated over the visible wavelengths). Through initial testing, modeling, and simulation, determine the range of contrast, switching speed, and expected lifetime of devices in Phase I and Phase II technology development. 

PHASE II: Further development and refinement of LWIR contrast changing technology suitable for use on military ground vehicles. Fabrication of a prototype panel of at least 16 infrared devices (comprising an area of at least 24” by 24”) to be characterized by the Government. Characterization will include outdoor performance experiments and indoor lifetime evaluation. The panel shall include a breadboard switching system which iterates between several patterns on demand; the switching system shall utilize open-source architecture and commands such that the Government can implement its own patterns in the future. The devices must maintain their hue while maintaining a visible reflectivity within 10% during infrared switching (reflectivity integrated over the visible wavelengths). Additionally, two distinct colors must be demonstrated (i.e., devices must have the option of two contrasting colors found in standard Army camouflage pattern schemes). 

PHASE III: Other than the IFF/CIP development for the military, the materials developed in this SBIR could result in thermal switching devices that help with heating and cooling of large surface areas such as rooftops and storage containers. 

REFERENCES: 

1: 1D. M. Douglas, T. Swanson, R. Osiander, J. Champion, A.G. Darrin, W. Biter, and P. Chandrasekhar, "Development of the variable emittance thermal suite for the space technology 5 micro satellite," AIP Conference Proceedings 608, 204 (2002).

2:  2F. Lang, H. Wang, S. Zhang, J. Liu, and H. Yan, "Review on variable emissivity materials and devices based on smart chromism," International Journal of Thermophysics 39, 6 (2018).

KEYWORDS: Emissivity, Emittance, IFF Systems, Materials Science, Infrared Transmitters, Long-wavelength Infrared Radiation 

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