Illuminate systems8/18/2023 ![]() The imager, called U8000, was developed for the Army for use in next-generation military systems such as thermal weapon sights, digitally fused enhanced night-vision goggles, driver's vision enhancers and unmanned aerial systems. The Reconnaissance, Surveillance and Target Acquisition (RSTA) group at DRS Technologies (Dallas, Texas, U.S.A.) has developed a VOx uncooled focal-plane array (UFPA) consisting of 17-µm pixel-pitch detectors measuring 1,024 × 768. Wavelength response for various visible/IR detector materialsįor now, next-generation systems for defense are moving to 17-µm pitch. The technology has come a long way in a short time to improve performance, noise and array size, but many barriers remain. A nonexhaustive list of companies pursuing 15-µm pitch sensors includes Raytheon (Waltham, Mass., U.S.A.), Goodrich/Sensors Unlimited (Princeton, N.J., U.S.A.), DRS Technologies (Parsippany, N.J., U.S.A.), AIM INFRAROT-MODULE GmbH (Heilbronn, Germany), and Sofradir (Châtenay-Malabry, France). Currently, sensors with 15- and 12-µm pixel pitch are in the development stage in several places, and they have even been demonstrated at SWIR, MWIR and LWIR wavelengths using mercury cadmium telluride (HgCdTe or MCT, also called CMT in Europe) and indium antimonide (InSb) with simple readout integrated circuits. One critical way to do that is to squeeze more pixels onto each sensor, reducing the pixel pitch (the center-to-center distance between pixels) while maintaining performance. So reducing cost is of the utmost importance. But these semiconductor materials are expensive: a glass lens for visible imaging that costs $100 may cost $5,000 for Ge in the IR, according to Chris Bainter, senior science segment engineer at FLIR Advanced Thermal Solutions (South Pasadena, Calif, U.S.A.). ![]() Indium gallium arsenide (InGaAs) and germanium (Ge) are common in IR sensors. Uncooled microbolometers can be fabricated from vanadium oxide (VOx) or amorphous silicon. Imaging in the IR can involve a wide range of detectors or sensors. Also, SWIR imaging occurs at 1.5 µm, which is an eye-safe wavelength preferred by the military. ![]() The SWIR region bridges the gap between visible wavelengths and peak thermal sensitivity of infrared, scattering less than visible wavelengths and detecting low-level reflected light at longer distances-ideal for imaging through smoke and fog. Glass lenses can transmit from visible through the NIR and SWIR region. The SWIR portion of the spectrum ranges from 1.7 µm to 3 µm or so. The NIR portion of the spectrum is typically defined as ranging from the end of the visible spectrum around 900 nm to 1.7 µm. The infrared spectrum, adjacent to the visible part of the spectrum, is split into four bands: near-, short-wave, mid-wave, and long-wave IR, also known by the abbreviations NIR, SWIR, MWIR and LWIR. A seemingly impossible task such as imaging a threat moving behind foliage at night is made possible by new developments in IR technology, including sensors fabricated using novel materials, decreased pixel pitch (the center-to-center distance between pixels) and improved cooling and vacuum technology. The infrared (IR) wavelengths are an important focus of military and defense research and development because so much of surveillance and targeting occurs under the cover of darkness. While the specifics are hard to pin down, the trends are evident. This means companies are not only tight-lipped about disclosing the secrets of military technology (as usual), but that they are even more guarded about the proprietary advances that make them competitive. In addition to the ever-present demand to reduce size, weight and power, the trend in the military and defense industry is to develop technology that cuts costs-in other words, to do more with less. Global defense budgets are subject to cuts like everything else, with so many countries experiencing debt and looming austerity measures at home. A Black Hawk helicopter is thermally imaged with a high-definition video camera at MWIR wavelengths near Nellis Air Force Base in Nevada.
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