THALES have developed for volume manufacture two high performance low cost thermal imaging cameras based on the THALES Research & Technology (TRT) 3<sup>rd</sup> generation gallium arsenide long wave Quantum Well Infrared Photodetector (QWIP) array. Catherine XP provides 768 x 575 CCIR video resolution and Catherine MP provides 1280 x 1024 SXGA video resolution. These compact and rugged cameras provide 24-hour passive observation, detection, recognition, and identification in the 8 to 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 75 K, 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.
Successful past experience of implementing long wave MCT 1st and 2nd Generation thermal imagers has demonstrated to THALES Optronics that MCT presents difficult challenges when correcting non-uniformity errors caused by rapidly changing detector element gain and offset drifts. These problems become even more demanding when the move is made from long linear arrays to focal plane arrays due to the significantly larger number of detector elements. Relaxation of these demands would make a significant impact on the price/performance trade which inevitably occurs in a camera development. In recognition of the need to offer UK MOD best value, THALES Optronics has initiated a programme to achieve a SXGA resolution camera and is working with UK MOD, over a two year period, to investigate whether an alternative technology can maintain the high resolution required whilst achieving a downward step change in price. The selected technology is 3rd Generation Gallium Arsenide long wave Quantum Well Infra-red Photodiode (QWIP) chosen because initial indications are that drift rates are orders of magnitude slower than MCT. The programme involves studies to determine effects of defect clusters, bimodalism, non-uniformity correction levels and higher than normal operating temperatures on achieving acceptable performance, including logistics, in user scenarios whilst maximising detector yield. Development of demonstrator IR camera hardware (technology readiness level 6/7) based on a THALES Research & Technology QWIP array is also part of the programme.
As the temporal NETD of TI imaging systems decreases attention increasingly turns to the uniformity of the presented imagery. This uniformity begins to limit the ultimate recognition and identification ranges of the system. This is true both of staring arrays and long linear detector based systems. This paper discusses the design, implementation and integration of a very high performance non-uniformity correction approach within the STAIRS C production SXGA resolution camera and presents preliminary findings.
In engagement scenarios increasing battlefield emphasis on the trade-off between long stand-off ranges, adverse weather capability and high probability target identification has resulted in the need for an SXGA resolution IR Sensor. Leading on from previous collaborative work with QinetiQ (formerly the UK Defence Evaluation and Research Agency) the UK MoD has awarded a contract, the STAIRS C programme, to Thales Optronics to develop to production such an IR Sensor thus ensuring this leading technology is available to meet the needs of advanced weapon systems and platforms of the future. A UK industry team has been formed to implement an optimisation programme for the productionisation and future applications of STAIRS C modules and the first of a number of UK MoD programmes has selected STAIRS C for a major Air Defence role. The STAIRS C programme has set the demanding requirement of doubling the target identification range of current in-service IR sensors whilst maintaining or improving the situational awareness (Field of View). The programme, technical specification and imaging capability achieved are reviewed in the paper.
Dual field of view sensors form the basis of many current IR systems. Emerging scenarios, however, are beginning to call for a wide range of field coverage, and are stretching the capabilities of dual field systems beyond the point where a comfortable balance of fields is obtainable. Provision of a 3rd field of view opens up an extended range of operational possibilities, and in many scenarios offers a sufficient level of functional availability when weighted against the cost of additional on-board FLIRs. The design evolution of a lightweight and compact triple field optical system is described. The system features a novel, optimum geometry carousel, which enables provision of 3 fields with a single mechanism. The design is modular and flexible, offering ratios up to 20:1 between the widest and narrowest field. Hybrid optical element assist in achieving performance with minimum element count, and a variant of the design featuring special materials (GaAs/KRS5) offers extended temperature capability and athermalization for specific applications. Configuration constraints are defined, limitations of alternative approaches explored, and characteristics of the preferred design are presented. Opto-mechanical design features are described which take advantage of the novel FOV change concept to produce a stable, balanced system which can offer advantages compared with a zoom in the operational environment. The modular nature of the configuration, which permits field of view and scanner interfacing to be readily tailored to suit any specific application while retaining commonality of main structural components and mechanisms, is also illustrated.