Designing a cryogenic camera is a good strategy to miniaturize and simplify an infrared camera using a cooled
detector. Indeed, the integration of optics inside the cold shield allows to simply athermalize the design,
guarantees a cold pupil and releases the constraint on having a high back focal length for small focal length
systems. By this way, cameras made of a single lens or two lenses are viable systems with good optical features
and a good stability in image correction. However it involves a relatively significant additional optical mass
inside the dewar and thus increases the cool down time of the camera. ONERA is currently exploring a
minimalist strategy consisting in giving an imaging function to thin optical plates that are found in conventional
dewars. By this way, we could make a cryogenic camera that has the same cool down time as a traditional dewar
without an imagery function. Two examples will be presented: the first one is a camera using a dual-band
infrared detector made of a lens outside the dewar and a lens inside the cold shield, the later having the main
optical power of the system. We were able to design a cold plano-convex lens with a thickness lower than 1mm.
The second example is an evolution of a former cryogenic camera called SOIE. We replaced the cold meniscus
by a plano-convex Fresnel lens with a decrease of the optical thermal mass of 66%. The performances of both
cameras will be compared.
Cooled IR technologies that offer high performances are at the top of DEFIR’s priority list. We have been
pursuing further infrared developments on future MWIR detectors, such as the VGA format HOT detector that
operates at 150K and the 10μm pitch IR detector which gives us a leading position in innovation In the same
time Scorpio LW expands Sofradir's line of small pixel pitch TV format IR detectors from the mid-wavelength
to the long-wavelength, broadening the performance attributes of its long wave IR product line. Finally, our dual
band MW-LW QWIP detectors (25μm, 384×288 pixels) benefit to tactical platforms giving an all-weather
performance and increasing flexibility in the presence of battlefield obscurants.
These detectors are designed for long-range surveillance equipment, commander or gunner sights, ground-toground
missile launchers and other applications that require higher resolution and sensitivity to improve
reconnaissance and target identification. This paper discusses the system level performance in each detector
MCT technologies under development in France address strategic operational needs. This includes better identification
range as well as lighter weight requirement, operation at higher detector temperature and cost reduction issues.
This paper describes the status of MCT IR technology in France at Leti and Sofradir. A focus will be made on hot
detector technology for SWAP applications.
Solutions for high performance detectors such as dual bands or megapixels will be discussed. In the meantime, the
development of avalanche photodiodes, integrated optics, or TV format with digital interface is key to bring customers
Low IR input flux conditions are answering different system applications as gas detection needs, active imagery,
very long ranges detection and identification and some scientific applications. Then for other applications like
ground applications, some system design trade-off could be made between thermal performance and identification
and equipment size and cost.
The improvement of the infrared (IR) Mercury Cadmium Telluride (MCT) detectors performances impacts the
measurement constraints and these advanced detectors require new types of electro-optical tests. In this paper, the
development at Sofradir of advanced electro-optical test benches and test methods are described as well as the final
performances measured on the advanced MCT IR detectors.
Proc. SPIE. 6295, Infrared Detectors and Focal Plane Arrays VIII
KEYWORDS: Staring arrays, Infrared detectors, Signal to noise ratio, Optical transfer functions, Mercury cadmium telluride, Sensors, Diodes, Modulation transfer functions, Analog electronics, Semiconducting wafers
The InfraRed staring arrays are more and more compact and offer system solutions in the different IR wavebands. The HgCdTe (Mercury Cadmium Telluride / MCT) material and process, as well as the hybridization technology, have been taken to an even more advanced level of sophistication to achieve these new staring arrays high performances. Latest developments allow progress at different stages of products offered by SOFRADIR. Uniformity of Focal Plan Arrays (FPA) is improved, read-out circuits propose new functions as the analogic to digital conversion, and the reliability of the whole dewar detector and cooler assembly is increased. New products take advantages on these progresses. In mid-wave (MWIR), 1280x1024 MCT detector available in a tactical dewar is presented.