Air Force

Integrated infrared optical antenna and sensor for object tracking

Faster, lower-cost technology incorporates automatic wavelength-selective detection

Sensors

A team of U.S. Air Force scientists working at the Air Force Research Laboratory has recently developed an antenna and transducer sensor for multispectral imaging, detection, and tracking. The patented technology is available via patent license agreement to companies that would make, use, or sell it commercially.

Infrared detectors generally consist of photoconductors, photo-emissive detectors, and photodiodes. These detectors do not have an inherent capability for wavelength selective detection without external media such as spectral filters and phase and diffraction gratings. In addition, the high cost of quality Mercury-Cadmium-Telluride (MCT), Indium Gallium Arsenide (InGaAs) and Indium antimonide (InSb) focal-plane arrays (FPAs) become prohibitive for very large area infrared detectors. Finally, the capacitance of each detector pixel is directly related to its size and presents challenges for accurate, extremely fast (sub-nanosecond) object tracking. In order to achieve good signal-to-noise performance and very fast response, existing detectors may also require cryogenic cooling to prevent the thermal generation of charge carriers, limiting platform mission time and increasing power consumption. The readout integrated circuit (ROIC) adds considerable weight and cost to the detector. Based on established technologies, these detectors are also susceptible to an array of countermeasure systems, do not have inherent wavelength-selective detection, and require complex signal processing algorithms for object tracking.

Accordingly, there is a need for an object tracking technology with sub-nanosecond time resolution using a detector inherently capable of wavelength-selective detection and without expensive detector materials that require cryogenic cooling. In response, AFRL scientists have developed an inexpensive, high speed, ambient temperature, and spectrally selective sensor.

The invention includes a visible shortwave infrared (VIS-SWIR) integrated antenna and polaronic organic sensor containing a doped, conjugated, organic polymer-graphene thin film acting as a fast, room temperature signal transducer and a dipole antenna. The antenna acts as a wavelength selective, resonant spectral filter.

The sensor may be fabricated in linear arrays of 20 to 40 antenna-polaronic integrated sensors connected in series. The integrated sensor array may be designed to operate at selected VIS-SWIR wavelengths. Signals from each array may be read out by pulse capture hardware and transferred to a sensor-specific processing unit to be processed by algorithms that can identify and/or track an object from the electromagnetic radiation emitted. Although the sensors may be cooled, they can also operate at ambient temperatures.

The integrated sensor arrays also have a native object tracking ability using simple signal processing algorithms that utilize a reduced data set. As a result, wavelength-selective detection and object tracking is simplified while the operating temperature of the detector may be increased. Actual detector dimensions depend on the desired resonance wavelength of the antennas, the required spatial resolution of the detector, and the number of wavelength bands to detect, among other factors.

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