High Performance Thermal Imaging Research Articles

Achromatic and Coma-Corrected Hybrid Meta-Optics for High-Performance Thermal Imaging.

Long-wave infrared (LWIR) imaging, or thermal imaging, is widely applied in night vision and security monitoring. However, the widespread use of LWIR imagers is impeded by their bulky size, considerable weight, and high cost. While flat meta-optics present a potential solution to these limitations, existing pure LWIR meta-optics face constraints such as severe chromatic or coma aberrations. Here, we introduce an approach utilizing large-scale hybrid meta-optics to address these challenges and demonstrate the achromatic, coma-corrected, and polarization-insensitive thermal imaging. The hybrid metalens doublet is composed of a metasurface corrector and a refractive lens, featuring a full field-of-view angle surpassing 20° within the 8-12 μm wavelength range. Employing this hybrid metalens doublet, we showcase high-performance thermal imaging capabilities both indoors and outdoors, effectively capturing ambient thermal radiation. The proposed hybrid metalens doublet holds considerable promise for advancing miniaturized, lightweight, and cost-effective LWIR optical imaging systems.

Microphotonic thermal imaging

High-performance thermal imaging technology typically involves using cryogenically cooled devices. In the future, detectors based on arrays of tiny optical resonators could lead to sensitive, rapid, thermal imaging at room temperature.

THALES long wave QWIP thermal imagers

THALES have developed for volume manufacture high performance low cost thermal imaging cameras based on the THALES Research Technology (TRT) third generation gallium arsenide long wave QWIP array. Catherine XP provides 768×575 CCIR video resolution and Catherine MP provides 1280×1024 SXGA video resolution. These compact and rugged cameras provide 24h passive observation, detection, recognition, identification (DRI) in the 8–12μm range, providing resistance to battlefield obscurants and solar dazzle, and are fully self contained with standard power and communication interfaces. The cameras have expansion capabilities to extend functionality (for example, automatic target detection) and have network battlefield capability. Both cameras benefit from the high quantum efficiency and freedom from low frequency noise of the TRT QWIP, allowing operation at 75K, low integration times and non interruptive non uniformity correction. The cameras have successfully reached technology readiness level 6/7 and have commenced environmental qualification testing in order to complete the development programmes. These latest additions to the THALES Catherine family provide high performance thermal imaging at an affordable cost.

Design and development of a high-performance third-generation hand-held thermal camera

A high-performance hand-held thermal imaging camera has been developed, based on a 320256-element InSb infrared focal plane array FPA operating in the medium-wave infrared region. The primary design objective was a low-cost, compact, lightweight, and por- table thermal camera with a recognition range of 2 km. A staring FPA based on InSb technology with long and variable integration time pro- vides the answer best suited to these requirements. The system pro- vides such features as two-point and adaptive nonuniformity correction, bad-pixel detection and replacement, dynamic range compression, con- trast and edge enhancement, histogram equalization, and digital scan conversion for CCIR-B-compatible output. The design methodology and the performance are presented. © 2006 Society of Photo-Optical Instrumentation

InAs/GaSb type‐II superlattices for single‐ and dual‐color focal plane arrays for the mid‐infrared spectral range

Focal Plane Arrays for high-performance thermal imaging systems operating in the mid-infrared spectral range between 3–5 µm have been realized by type-II InAs/GaSb short-period superlattices. A fully operational 256 × 256 camera system showing a noise equivalent temperature difference below 10 mK is presented. The suitability of InAs/GaSb type-II superlattices for next generation thermal imagers is demonstrated with the first 288 × 384 dual color demonstrator camera which features a simultaneous and spatially coincident acquisition of two separate spectral regimes in the mid-infrared. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

High performance thermal imaging technology

Infrared (IR) thermal imaging (TI) has a relatively long history, with the first demonstration of the existence of infrared radiation in 1800 by William Herschel. Since that time the use of IR radiation for imaging has been most strongly connected with the military market and its need for night vision, from the first demonstration of infra-red photon detection during World War I, to the development of mercury cadmium telluride material at Malvern in the 1960s and the first staring arrays in the 1980s. Thermal imaging cameras have been shown to give a key military advantage, and it believed that all military campaigns waged in darkness by Western forces using thermal imaging have been successful.

Ten years of QWIP development at Fraunhofer IAF

We report on our quantum well infrared photodetector (QWIP) developments aimed at high-performance thermal imaging with two-dimensional focal plane arrays (FPA). Due to the limited charge storage capacity of todays readout circuits, high internal quantum efficiencies in combination with moderate responsivities and noise currents are desirable in order to optimize thermal resolution. Using FPAs comprising photoconductive QWIPs, very good noise-equivalent temperature differences better than 10 mK are obtained at small applied electric fields of 3–5 kV/cm. We also summarize the detection properties of photovoltaic “low-noise” QWIPs. In this novel device, the photoexcited-carrier mean free path corresponds to only one period of the active region and the noise associated with carrier capture is suppressed. Further improvement of the temperature resolution, in combination with an extremely large dynamic range, has been achieved using FPA cameras based on this detector concept. At present, QWIP FPAs achieve the best temperature resolution of any detector technology operating in the long-wavelength infrared atmospheric window.

Materials for high performance infrared detectors: status and trends

The purpose of this paper is to survey and assess recent trends in the field of detector materials for infrared focal plane arrays (IRFPAs) applicable in high-performance thermal imaging systems. Considered are II-VI, III-V and IV-VI compounds (including hetero structures and superlattices) with respect to their actual and potential performance, reliability and producibility. Addressed are growth methods for thin films of high uniformity as regards physical, optical, and electrical properties. The main efforts are found presently to concentrate on establishing growth methods for material systems and structures appropriate for more efficient manufacturing of IRFPAs. It is concluded that HgCdTe continues to be the most important material for infrared imaging in the wavelength region between 8 and 12 μm.

The practical realisation and performance of sprite detectors

This paper details the practical realisation of a novel device for use in thermal imaging systems—the SPRITE detector. This type of detector incorporates signal processing in the element by providing the time delay and integration functions, normally performed off the focal plane in conventional serial scanned systems. The detector has particular significance for high performance thermal imagers, allowing a more compact design with simplified electronics. The development of the fabrication technology for SPRITE is described together with the performance of devices for operation in both the 8–14 and the 3–5 μm bands.

Focal plane temperature stability requirements for thermal imaging systems using extrinsic Si:In detectors

The use of Si:In IR detectors in high performance thermal imaging systems imposes a stringent requirement on the temperature stability of the focal plane. In this paper, we calculate that temperature fluctuations of the focal plane must be kept to less than either 12 mK or 1.2 mK for thermal imaging systems capable of resolving 0.1 degrees C or 0.01 degrees C temperature differences, respectively, in the scene being imaged.