Keeping one step ahead of our adversaries is top priority for security forces with terrorist threats growing daily around the world. Intelligence, surveillance and reconnaissance are the core situational awareness tools for the global war on terrorism (GWOT). Just as night vision equipment has denied terrorists the cover of darkness for more than a couple of decades, emerging shortwave infrared imaging technology is now removing weather and environmental limitations from the ISR equation.
Shortwave infrared exploits the third and final atmospheric window in the infrared spectrum. SWIR, long the domain of the high altitude U-2 spy plane with its cryogenically-cooled focal plane array (FPA) technology, has powerful capabilities not widely known outside the intelligence community until recently. SWIR makes long slant range imaging possible under practically any conditions. A revolution in imaging has recently been developed via breakthrough, indium gallium arsenide (InGaAs) FPA technology, resulting in lighter weight, more compact cameras. These new uncooled InGaAs imagers offer the advantages of the short-wave infrared spectrum to see beyond the visible, and because of their ultra-compact design, they can be implemented on the smallest UAVs (unmanned aerial vehicles) and man-portable platforms.
Powerful Capability in a Small Package
Figure 1 shows the SU640KTSX InGaAs SWIR imager from Sensors Unlimited, Inc. (Princeton, NJ) in its OEM configuration. This compact imaging sensor weighs less than 90g and is capable of full motion video at a 640 x 512 pixel resolution from daylight to starlight while operating uncooled at room temperature. The SWIR camera features extremely high-quantum-efficiency InGaAs technology with excellent spectral response from 0.9 to 1.7 microns and extending down to 0.7 microns in the NIR/SWIR version, a broad spectral range encompassing all the key battlefield laser wavelengths. Requiring as little as 2.5 watts of electrical power, the SU640KTSX is attracting a lot of interest for small UAV and man-portable applications.
Until recently, only visible, and to some extent long-wave, infrared (LWIR, 8 to 12 microns) imaging payloads had been flown on the smaller UAVs. The visible imagers could not be used at night, while uncooled LWIR microbolometers had limited sensitivity or resolution at long-range and were especially disadvantaged during dawn and dusk thermal crossovers. SWIR brings a lot to the table, not only bridging the capability gaps of the other technologies, but also offering the most comprehensive all weather, all environmental, and around-the-clock operability in a single uncooled sensor package.