The recent advent of high operating temperature infrared detectors allowed operating them at temperatures in excess of 150K without compromising performance indices typical of their 77K predecessors. These substantially relaxed cooling constraints along with a fundamentally higher coefficient of thermodynamic performance called for the development of a next-generation of low size, weight, and power cryocoolers purposely tailored for such high operating temperature detectors. Unfortunately, the most up-to-date low size, weight, and power cryocoolers are no more than downscaled and slightly lower-priced replicas of their low temperature predecessors. They commonly rely on gaseous helium as the working agent, metal stacked-screens regenerative heat exchangers, “moving magnet” dual-piston compressors, pneumatic expanders driven by differential pistons, mechanical springs, etc. Because of the inherent limitations, the currently achieved reliability and cost indices still prevent the broad use of cooled infrared imaging in the price-conscious and highly competitive commercial segment of the infrared imaging marketplace. From the very moment of its inception in 2018, CryoTech focused on disruptive innovation, enabling drastic reduction of ownership costs by deploying alternative, cost-effective technological solutions. The list of novelties includes but is not limited to: alternative working agent, low-cost microfiber regenerative heat exchanger, “moving iron” single-piston compressor with optional tuned dynamic counterbalancer, rodless pneumatic displacer, magnet springs, etc. The authors present the outcomes of the full-scale feasibility study and prototype life testing.
Operating infrared detectors at cryogenic temperatures is vital for attenuating intrinsic thermally-induced noise, thus enabling long working ranges, short integration times, high spatial and temperature resolutions along with other advantages.
Unfortunately, the high costs of integrated dewar/detector/cooler assemblies prevent the broad deployment of cooled infrared technology in the price-sensitive and highly competitive commercial market. Uncooled infrared technology, although inferior in performance, is more affordable and, therefore, more ubiquitous.
Extending working ranges of uncooled infrared detectors, however, may lead to using expensive and bulky “fast” optics. In a combination with added cost, weight and mechanical complexity of host structures, this may wipe out inherent cost/bulk advantages of uncooled imagers. In some cases, therefore, the cooled infrared imager may be superior in terms of attainable performance, bulk, and system cost.
Cryogenically cooled infrared detectors are known to have better temperature resolution and shorter integration time as compared to the uncooled “competitors”. These advantages allow for longer detection distances, better spatial resolution and the ability to detect fast moving objects. However, high ownership cost of the mechanical cryogenic refrigerator, along with tough export regulations, prevent the widespread deployment of cryogenically cooled infrared imagers in the commercial marketplace. CRYOTECH LTD reports on the development of cost-effective, low size, weight, and power cryogenic solutions for commercial high operational temperature infrared imagers. The authors present the outcomes of the feasibility study, predictions of theoretical performance along with size and weight assessments.
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