Clustering micro satellites in cooperative fly formation constellations leads to high-performance space systems. The only way to achieve high-speed communication between the satellites is by a laser beam with a narrow divergence angle. In order to make the communication successful three types of focal plane detector arrays are required in the communication terminal: acquisition, tracking and communication detector arrays. The acquisition detector array is used to acquire the neighbor satellite using a wide field-of-view telescope. The tracking detector provides fast, real time and accurate direction location of the neighbor satellite. Based on the information from the acquisition and tracking detectors the receiver and transmitter maintain line of sight. The development of large, fast and very sensitive focal plane detector arrays makes it possible to implement the acquisition, tracking and communication with only one focal plane detector array. By doing so it is possible to reduce dramatically the size, weight, and cost of the optics and electronics which leads to lightweight communication terminals. As a result, the satellites are smaller and lighter, which reduces the space mission cost and increases the booster efficiency. In this paper we will present an overview of the concept of integrated focal plane arrays for laser satellite communication. We also present simulation results based on real system parameters and compare different implementation options.

Compact small-pitched infrared focal plane arrays (FPA) having ultimate performance are of the great interest for development and production of state-of-the-art special and common use thermal imaging systems lighter in weight and with lower energy consumption. Novel MBE-grown Hg_1-xCd_xTe epitaxial multi-layer structures are considered perspective for manufacturing of such FPA. Objective of the present work was to examine the impact of small-pitched Long-Wave Infrared (LWIR) Hg_1-xCd_xTe photoconductor device performance on variation of background flux density. Peak wavelength λ_p was ranged from 10.5 to 11.5 μm at 78-100 K. High performance small active area photoconductors based on MBE-grown multi-layer structures consisting of homogeneous narrow-gap n-Hg_1-xCd_xTe absorbing layer (n-absorber) both side blocked by thin graded-gap Hg_1-xCd_xTe layers have been fabricated and examined. Availability of innovative Hg_1-xCd_xTe epitaxial material (half-finished products of photoconductors - three-layer sensitive structures grown by MBE in single run) gives opportunity to manufacture and offer versatile detectors with flexible tuning of electro-optical parameters. Multi-element (2 x 32=64 elements) Hg_1-xCd_xTe photoconductors with pixel's active area size 30 μm x 30 μm and pitch 45 µm were tested. Electro-optical measurements have shown improved value of peak responsivity and detectivity close to theoretically predicted for model photoconductor.

Infrared systems require today high resolution detectors, in miniaturized configurations, and with cost reduction. To answer these requirements, SOFRADIR has taken its HgCdTe (Mercury Cadmium Telluride/ MCT) material and process as well as its hybridization technology to the next even more advanced level of sophistication, and is now offering large format detectors with graduated levels of performances regarding pitch size and cryogenics. For large format LW detectors, Sofradir takes advantage of the Thales Research Technology (TRT) Quantum Well Infrared Photodetector (QWIP) process working at up to 75K to offer a very compact large array QWIP IDDCA. For Mid Wave applications, the SCORPIO 15 μm pixel pitch TV format (640×512) HgCdTe detector is released, for operation above 100K, allowing the use of 0.3W microcooler with miniaturized cryogenics, either for new compact systems or for the direct upgrade of existing 30µm pitch TV/4 format systems. This new 15μm pitch HgCdTe TV format exhibits high performances in optimized very small size cryogenics in order to achieve a cost effective production level. Doing so, this detector will become the most affordable large format at production level in the coming years. For Long Wave applications two new detectors are launched: the HgCdTe approach for high frame rate applications with a medium format detector (25μm pitch 384×288), and the large format (640×512 20μm) QWIP approach for high resolution imagery applications. These LW detectors are offered with microcoolers and miniaturized cryogenics. The performances of these new IR detectors are presented in this paper as well as the development trends for even higher resolution IR detectors at Sofradir.

For the past few years SCD has been developing a series of Infra Red (IR) detectors based on the well established technologies of InSb diodes and the most advanced analogue and digital signal processors. These detectors exhibit special modes of operation combined with a high level of performance, which enables the detectors to be optimized within a large variety of applications. Among these applications the most demanding are considered to be those related to Missile Warnings Systems (MWS) and firing identification. For these high-end applications, a combination of suitable operation modes and high performance is required, including: large dynamic range, high frame rate, high sensitivity at low signal and a smooth transition of operation mode from frame to frame. The first detector developed for MWS is the "Blue Fairy" detector which has 320x256 elements with a 30μm pitch. After the "Blue Fairy" a family of new generation digital detectors was developed, starting with "Sebastian". Sebastian is based on a novel digital Focal Plane Processor (FPP) with a 20μm pitch and a format of 640×512. Next, for the mid format, a digital detector with 480×384 elements was developed, based on the same concept as the large format Sebastian detector but with some additional functionality. In this paper the special features and performance of these detectors are presented showing their advantages for MWS applications.

Antimonide Based Compound Semiconductors (ABCS) and a new family of advanced analogue and digital silicon read-out integrated circuits form the basis of the SCD 3rd generation detector program, which builds on the firm platform of SCDs existing InSb-FPA technology. We have devised a staged roadmap at SCD which begins with epitaxial InSb mesa diodes and gradually increases in technological sophistication. In the initial stages we have focused in particular on In_1-zAl_zSb alloys grown on InSb by Molecular Beam Epitaxy (MBE). Some of our achievements with these materials are presented in this paper. For epitaxial InSb (z = 0), we demonstrate the performance of Focal Plane Arrays (FPAs) with a format of 320x256 pixels, at focal plane temperatures between 77K and 110K. An operability has been achieved which is in excess of 99.5%, with a Residual Non-Uniformity (RNU) at 95K of less than 0.03% (standard deviation/dynamic range) between 15 and 80% well fill. Moreover, after a two point Non-Uniformity Correction (NUC) has been applied at 95K, the RNU remains below ~0.1% at all focal plane temperatures down to 85K and up to 100K without the need to apply any further correction. This is a major improvement in both the temperature of operation and the temperature stability compared with implanted diodes made from bulk material. We also demonstrate rapid progress in the development of epitaxial InAlSb FPAs with comparable operability and RNU to the InSb FPAs but which exhibit lower dark current and offer a range of cut-off wavelengths shorter than in InSb. These FPAs are intended for temperatures of operation in excess of 100K.

Quantum Well Infrared Photodetectors (QWIPs) based infrared focal plane arrays (FPAs) are commercially available in the single color. QWIP Technologies, Inc. provides a number of QWIPCHIPTM FPAs available in the single-color, dual-color and even multiple-color, as well as varieties of physical formats in the infrared range. In this paper, we discuss the research and development efforts currently ongoing at QWIP Technologies on dual-color, visible-NIR/LWIR FPAs, and the development of a four-color QWIP-based FPA. These multicolor systems are being developed to meet the needs of a number of military applications including land mine detection. Land mines inhibit the safe movement of troops and produce chaos in countries struggling for socio-economic stability long after the cessation of hostilities. This paper will describe the efforts to develop a near multi-color QWIP sensor for mine detection. The core of the discussion will include highlights of a two-color LWIR QWIP sensor system designed to provide uniform, high spatial resolution, multi-color co-registered imagery and possess negligible spectral cross-talk. Through these efforts, The Defense Advanced Research Projects Agency (DARPA) is completing the development of a visible/infrared mine detection system, which when deployed on an airborne platform, would increase the war fighting effectiveness has sponsored the current developments.

A photovoltaic intersubband detector based on electron transfer on a cascade of quantum levels is presented: a Quantum Cascade Detector (QCD). The highest photoresponse of intersubband transition based photovoltaic detectors is demonstrated: 44 mA/W at null bias. Further improvements permit to suppress the leakage current and to increase the resistivity R0A. Useless cross-transitions have been eliminated finally leading to a high resistance narrow band photodetector with a Johnson noise detectivity at 50 K comparable to QWIPs. Because they work with no dark current, QCDs are very promising for small pixel and large focal plane array applications.

Uncooled infrared focal plane arrays are being developed for a wide range of thermal imaging applications. Developments are focused on the improvement of their sensitivity enabling the possibility of reducing the pixel pitch in order to decrease the total system size and weight by using smaller optics. We present the ULIS second generation technology used for producing 320 x 240 / 384 x 288 and 160 x 120 IRFPA with a pixel pitch of 35 μm. This enhanced technology has been developed by CEA / LETI since 2001 and transferred to ULIS in 2003. The device architecture will be described. These device are well adapted to high volume military applications (i.e. thermal weapons sight, enhanced driver vision) or commercial applications (non contact thermometers, thermal imaging cameras...) where system specifications are the result of a trade-off between pixel pitch, performance and system weight and volume. We have developed for these devices low cost packages. IRFPA electro-optical characterization is presented.

An Adaptive Focal Plane Array (AFPA) device that enables a "chip scale" imaging spectrometer is being developed. The AFPA device consists of an array of MEMS tunable filters that is intimately coupled to a dual band IR FPA. The MEMS filters provide narrowband tuning in the LWIR and simultaneous broadband imaging in the MWIR. Each filter element can be independently tuned. In the current design, each filter tunes the wavelength of pixel subarrays. Ultimately, filter size will be reduced to achieve independent wavelength tunability for each pixel element. This unique architecture of an AFPA device enables adaptive spectral analysis of the scene. Rather than collecting the complete hyperspectral cube, methods being developed will enable selection of spatially optimized spectral band sets for a variety of targets and materials that are selected "on-the-fly" to maximize the contrast between the local background and the target or material to be identified. The analyzed LWIR spectral information may then be overlaid with a pixel registered high resolution MWIR image.

Many modern imaging and surveillance systems contain more than one sensor. For example, most modern airborne imaging pods contain at least visible and infrared sensors. Often these systems have a single display that is only capable of showing data from either camera, and thereby fail to exploit the benefit of having simultaneous multi-spectral data available to the user. It can be advantageous to capture all spectral features within each image and to display a fused result rather than single band imagery. This paper discusses the key processes necessary for an image fusion system and then describes how they were implemented in a real-time, rugged hardware system. The problems of temporal and spatial misalignment of the sensors and the process of electronic image warping must be solved before the image data is fused. The techniques used to align the two inputs to the fusion system are described and a summary is given of our research into automatic alignment techniques. The benefits of different image fusion schemes are discussed and those that were implemented are described. The paper concludes with a summary of the real-time implementation of image alignment and image fusion by Octec and Waterfall Solutions and the problems that have been encountered and overcome.

A number of algorithms including moving target detection, video stabilisation and image enhancement have been described in the literature as useful in aerial reconnaissance scenarios. These algorithms are often described in isolation and require a base station for off-line processing. We consider the problem of designing a single image processing architecture capable of supporting these and other useful tasks in an embedded real-time system such as a semi-autonomous UAV. This paper describes our current algorithm suite and a versatile new architecture in development based on the formation of mosaic images. We show how these mosaics can be generated in real-time through fast image registration techniques and then exploited to accomplish typical aerial reconnaissance tasks. We also illustrate how they can be used to compress the video sequence. We show results from synthetic and real video using both software and hardware implementations. Our embedded hardware solution, its current algorithm suite and future developments are discussed.

An iris identification algorithm is proposed based on adaptive thresholding. The iris images are processed fully in the spatial domain using the distinct features (patterns) of the iris. A simple adaptive thresholding method is used to segment these patterns from the rest of an iris image. This method could possibly be utilized for partial iris recognition since it relaxes the requirement of using a majority of the iris to produce an iris template to compare with the database. In addition, the simple thresholding scheme can improve the computational efficiency of the algorithm. Preliminary results have shown that the method is very effective. However, further testing and improvements are envisioned.

ACMD, a new algorithm for Automatic Clustering of Multi-dimensional Data, is a practical method for the automatic segmentation of hyperspectral images into distinct homogenous groupings. The ACMD algorithm employs a top-down approach in which clustered pixels are iteratively split into two sub-clusters. Statistical improvement of homogeneity is tested after each split cycle using a proximity test (PT) and a variance test (VT). PT calculates the ratio of the number of pixels in the sub-cluster that are closer to the mathematical mean of the sub-cluster than they are to the mathematical mean of the original. VT calculates the ratio of the sum of the variance within the two new clusters to variance in the original cluster. ACMD allows a choice of analysis based on pre-normalized or non-normalized data sets using angular or Euclidean distance measurements. Splitting is halted when either the PT or VT ratio is greater than predetermined thresholds, unless VT variance in one new segment is ≤ 10^-3 of the original cluster. Analysis of synthetic data sets and of real hyperspectral data images is presented.

Thermal non-destructive approaches, passive and active, are widely used due to the outstanding advantages that offer in a number of applications and particularly for the assessment of materials and structures. In this work, different applications, employing either MWIR or LWIR thermographic testing, as well as passive and/or active approaches, depending on the application, concerning the assessment of various materials are presented. In a few instances, thermal modelling is also discussed and compared with the outcome of experimental testing. The following applications are reviewed: • Emissivity measurements. • Moisture impact assessment in porous materials. • Evaluation of conservation interventions, concerning: - Consolidation interventions on porous stone. - Cleaning of architectural surfaces. • Assessment of airport pavements. • Investigation of repaired aircraft panels. • Through skin sensing assessment on aircraft composite structures. Real time monitoring of all features was obtained using passive imaging or transient thermographic analysis (active imaging). However, in the composite repairs and through skin imaging cases thermal modelling was also used with the intention of providing supplementary results, as well as to demonstrate the importance of thermal contact resistance between two surfaces (skin and strut in through skin sensing). Finally, in order to obtain useful information from the surveys, various properties (thermal, optical, physical) of the examined materials were taken into account.

Diagnosing the reinforced concrete structures by using infrared thermography has become considerable in Japan. Infrared thermography has potential for detecting the defects, but is challenging due to unwanted thermal signals caused by surface roughness dirt, etc. To prevent from misdiagnosing, an innovative concept of merged thermal with visible images is proposed. Several key issues exist to capture the merged images: (1) alignment for the optical axes of an infra-red camera and digital still camera, (2) parallax correction between the thermal and visible images, (3) aberration correction for the lenses, and (4) adjustment of the image view angles. An experimental setup demonstrates an efficient diagnosing using the merged images.

During the last 12 years the European Union (EU) has financed the new member applicant countries of Central and Eastern Europe in their preparation for joining the EU. Based on this enlargement of the EU, funding for Cross Border Protection has been made available from the overall infrastructure improvement budget. Border protection was required in areas where border conflicts had taken place and to limit Illegal Immigration (II) and smuggling. After 9/11/2001, defence against terrorist activities will no doubt be added to the requirement. This paper describes the approach taken in the design of the latest "containerised" police and para military Mobile Surveillance Units (MSUs). This approach may also be considered for Homeland Security initiatives. These MSU's utilise standard road vehicles, and off-road variants, converted to use high performance military thermal imagers, such as SiGMA. In future the current, in service, MSUs will require increased sensor integration and networking to cover land and coastal borders. The underlying key is affordability for the police and para-military markets whilst retaining the highest performance derived from the latest SFPA military standard thermal imagers.

Thermal Imager for Dismounted Infantry (TIDI), is a UK MOD / Thales Optics Ltd. joint funded technology demonstrator programme and is part of the overall programme managed by QinetiQ. The aim of this programme is to evaluate and demonstrate a cost effective route to equipping the infantry soldier with a small, lightweight, rugged, short range, weapon mounted thermal imaging sight; intended for mass deployment. TIDI is an unusual programme in that the requirement was not rigidly defined in terms of a detailed specification. Instead, the requirement was expressed in terms of the question 'What weapon sight performance can be achieved for a volume production cost of 5000 Euro?' This requirement was subject to the constraints that the sight mass should be less than 500 g and the volume should be less than 500 ml. To address the requirements of this programme, Thales Optics Ltd. have performed a detailed trade-off analysis considering alternative uncooled LWIR sensor formats and technologies. The effect of using alternative sensors on the sight cost, mass, volume, power and performance has been compared. A design study has been performed concentrating on simplification of the optics, mechanics and electronics to minimise the overall sight complexity. Based on this analysis, a demonstrator sight has been designed that is cost effective and suitable for volume manufacture, whilst still offering useful performance to the user. Six technical demonstrator units based on this design have been manufactured and evaluated. This paper will give an overview of the work completed to date on the TIDI program, including a description of the demonstrator hardware and its performance.

During the last years the department of Optical Information Systems of the German Aerospace Center (DLR) developed a considerable number of imaging sensor systems for a wide field of applications. Systems with a high geometric and radiometric resolution in dedicated spectral ranges of the electromagnetic spectrum were provided by developing and applying cutting edge technologies. Designed for photogrammetry and remote sensing, such systems play an important role for security and defence tasks. Complete system solutions were implemented considering theoretical framework, hardware design and deployment, overall system tests, calibration, sensor operation and data processing. Outstanding results were achieved with the airborne digital sensor ADS40 and the micro satellite BIRD and its infrared camera payload. Future activities will focus on intelligent cameras and sensor webs. The huge amount of data will force the issue of thematic multi-sensor data processing which is to be implemented in real time near the sensor. In dependence on well defined tasks, combinations of several sensors with special properties will be placed on spaceborne, airborne or terrestrial platforms. The paper gives an overview about finished and current projects and strategic goals.

This paper describes a simple new optical technique for enhancing underwater target detection. Small-scale laboratory experiments using an idealised turbid medium consisting of polystyrene particles in water showed that detection ranges were up to an order of magnitude greater than those achieved using conventional methods. This work was carried out as part of the Electronic Systems Domain of the MOD Research programme.

We describe a new filter that simultaneously achieves spectral filtering and image replication to yield a two-dimensional, snapshot spectral imager. Filtering is achieved by spectral demultiplexing; that is without rejection of light; so optical throughput efficiency is, in principle, unity. The principle of operation can be considered as a generalisation of the Lyot filter to achieve multiple bandpasses. We report on the design and experimental implementation of an eight-band system for use in the visible and the design of an eight-band long-wave infrared system.

Infrared cameras are often used to capture high-speed digital video of scenes with enormous ranges in in-band brightness. A simple example of this would be a man standing next to a hot fire. Under normal operating conditions, it can be next to impossible to fully span a scene like this with the brightness dynamic range of an infrared camera. The brightest or hottest parts of the image will often be saturated, while at the same time the darkest or coldest parts of the scene may be buried in the noise floor of the camera and appear black in the image. Varying the exposure by changing the integration time is necessary to maximize the useful information recorded by the camera, but sometimes a single integration time is not enough to fully encompass a scene's variations. The technique of superframing consists of varying the integration time of the camera from frame to frame in a cyclic manner, then combining the resulting subframes into single superframes with greatly extended dynamic ranges. The technique and some sample data are described in this paper.

Component alignment slots and low attenuation hollow waveguides formed in silicon substrates by standard DRIE etching techniques provide the optical analogue of the electronic printed circuit board. In conjunction with conventional pick-and-place equipment this new hybrid integration technology will facilitate low cost mass production of compact, rugged, electro-optic microsystems for military platforms. In addition to the integration of discrete components (lasers, modulators, detectors, wave-plates etc) monolithic components are also feasible. These include: (i) the analogues of free space components - plane and curved mirrors, polarization splitters, diffraction gratings, MEMS devices for beam steering etc, and, (ii) hollow waveguide components - tapers for mode matching, proximity couplers, waveguide attenuators, and, a range of multimode interference (MMI) devices. MMI devices are attractive in that they offer a wide range of optical functionality from simple geometric structures, these include intensity and wavelength splitters and mixers. In this context the military efficacy of the technology is highlighted in the demonstration of a novel form of waveguide spectrometer for a new generation of hyperspectral sensors.

Fresnel Zone Plate Lenses (FZPLs) have been successfully coupled to infrared (IR) antennas producing a responsivity enhancement of about two orders of magnitude. However, their lateral extension may compromise their applicability in focal-plane-arrays (FPA) IR imagers, where the dimensions of the pixel are constrained by the FPA spacing. When designing optimum-gain FZPLs for FPAs, we are lead to the requirement of FZPLs operating at very low F/#s (marginal rays propagating at a large angle in image space). In this case, Finite-Difference Time-Domain techniques (FDTD) are used to refine the physical-optics modelling results, producing a result closer to the actual case encountered in a high-fill-factor FPA. In this contribution, we analyze the FZPL designs by using FDTD techniques. The main result of the FDTD computation is the gain factor defined as the ratio of the response of the IR antennas coupled with the FZPL, compared to the same antennas without the FZPL.

Wavefront coding involves the insertion of an asymmetric refractive mask close to the pupil plane of an imaging system so as to encode the image with a specific point spread function that, when combined with decoding of the recorded image, can enable greatly reduced sensitivity to imaging aberrations. The application of wavefront coding has potential in the fields of microscopy, where increased instantaneous depth of field is advantageous and in thermal imaging where it can enable the use of simple, low-cost, light-weight lens systems. It has been previously shown that wavefront coding can alleviate optical aberrations and extend the depth of field of incoherent imaging systems whilst maintaining diffraction-limited resolution. It is particularly useful in controlling thermally induced defocus aberrations in infrared imaging systems. These improvements in performance are subject to a range of constraints including the difficulty in manufacturing an asymmetrical phase mask and significant noise amplification in the digitally restored image. We describe the relation between the optical path difference (OPD) introduced by the phase mask and the magnitude of noise amplification in the restored image. In particular there is a trade between the increased tolerance to optical aberrations and reduced signal-to-noise ratio in the recovered image. We present numerical and experimental studies based of noise amplification with the specific consideration of a simple refractive infrared imaging system operated in an ambient temperature varying from 0°C to +50 C. These results are used to delineate the design and application envelope for which infrared imaging can benefit from wavefront coding.

The unique challenges encountered in the design of Infrared projection optics are described. Design examples covering the various avenues in solution space are presented each with their own distinct advantages and limitations. These candidate forms include refractive designs of differing materials, hybrid diffractive/refractive components and reflective assemblies. The results of these considerations thus better enable the systems engineer to anticipate the complexity and cost of scene projection optics.

Hyperspectral imaging has potential for detection of low-contrast targets in the presence of significant background clutter. We consider here the important case of detecting small targets as anomalies in a spatially cluttered natural background. In order to achieve a low false alarm rate, the properties of the background must be captured by the analysis procedure in sufficient detail to represent the full range of natural variation. Here we examine a statistical background model where background variations are represented by a sum of several multivariate normal probability distributions. The parameters of the statistical model are estimated using the stochastic expectation maximization (SEM) method. The quality of the resulting model's representation of natural backgrounds is discussed in terms of detection performance as a function of model complexity. Results are given for various illumination conditions and targets with different contrast to the background. We show that detection performance can be drastically improved by using multi-component background models, and that a low number of components is sufficient for detection of quite low contrast targets. The study is based on data with high spectral and spatial resolution from the Airborne Spectral Imager (ASI) hyperspectral sensor.

Multiband and hyperspectral imagers are widespread nowadays. Different approaches and technologies are used with this purpose. One of the main problems is to deal with the huge amount of information involved in hyperspectral images. Moreover, in the majority of the cases, the kind of technology used introduces some artifacts into the images. It is necessary to take them into account depending on types of application. In this paper we have applied a multivariate statistical technique known as principal components to characterize different artifacts introduced in hyperspectral imagers. The technique permits to obtain a set of "relevant filters" that could substitute the original system under special conditions.

The US Army RDECOM CERDEC Night Vision and Electronic Sensors Directorate of the US Army (NVESD) has developed a new target acquisition metric to better predict the performance of modern electro-optical imagers. The TTP metric replaces the Johnson criteria. One problem with transitioning to the new model is that the difficulty of searching in a terrain has traditionally been quantified by an "N50." The N50 is the number of Johnson criteria cycles needed for the observer to detect the target half the time, assuming that the observer is not time limited. In order to make use of this empirical data base, a conversion must be found relating Johnson cycles for detection to TTP cycles for detection. This paper describes how that relationship is established. We have found that the relationship between Johnson and TTP is 1:2.7 for the recognition and identification tasks.

Recent advances in the modeling of human observers using infrared and electro-optic sensors have provided remarkable accuracy in predicting performance. These advances center on a deeper understanding of the psychophysics involved in the target acquisition process. New insights into the role of noise as a limiter of sensor performance have resulted. A complete theory of target acquisition performance developed by Vollmerhausen et. al., is reviewed. A central element of this theory is the notion of minimum resolvable temperature (MRT) or minimum resolvable contrast (MRC). These functions can be subsumed under the idea of threshold vision. A general equation for threshold vision of an observer using an electro-optic sensor is presented. The relationship between threshold vision and MRT/MRC is shown. Channel models for the human perception are used to derive mathematical models for noise incorporating both the temporal and spatial response of the observer. The impact of noise found in electro-optical sensors on the threshold vision function and the target acquisition task is shown. The implications of the theory on laboratory characterization of sensors are explored. Future expansions of this theory are discussed.

Existing target acquisition models are effective in the prediction of Target Acquisition (TA) performance for monochrome or single band imagers (visible or infrared). There is currently no performance model for color imagers or fused imagery rendered on color displays. This study is a first step in extending the intensity contrast-based TA models to a three-dimensional color space. The monochrome TA model was developed with a variable, perceived signal to noise ratio threshold (SNRT), in contrast space, to determine target detection probability. In this research, we determined the noise-limited SNRT in the chroma direction for three equally spaced hue angles of CIELAB (Commission Internationale Eclairage L* A* B*) color space. The comparison of the chroma SNRT in these three hues of L*, a*, b* space that may allow an extension of the noise-limited sensor model to this three-dimensional space for color display modeling. Such a model improvement would result in a sensor performance model for both color imagers and for fused imaging color displays. This study investigates the target detection signal to noise threshold of single targets in a noisy color background. Noise is described in terms of signals of both target and noise at three different hues. Target images are presented to observers who are required to locate the target and select it with a mouse. The format of each experiment is that of a "forced choice" human detection perceptual experiment. The images are 64 pixel square with targets of one or four pixels. The results are the signal to noise thresholds in the chroma direction for the three different hues.

Automotive security is an increasing concern which requires new visual and detection system. Infrared imaging is a very good technological tool to perform such security enhancement. LETI Infrared Laboratory, as a IR technology designer, is a partner in the studies and development of such system for vision enhancement or security system analysis. Thus, we have developed two behavioural models of infrared focal plane array detectors: one in the Short Wave IR and the other in the Long Wave IR band. These detector models are used either in simulation platform aimed at evaluating the impact and use of infrared sensors in automotive and aeronautic applications or in order to test image processing algorithm on virtual component up to come. This work is a part of European Commission projects. The SWIR detector is calibrated with a 320x240 HgCdTe cooled FPA component from SOFRADIR and the LWIR one with an uncooled micro-bolometer array from ULIS (aSi:H microbolometer technology from LETI). The flexibility of the models permits to simulate cameras based on these component or new ones, using different read-out circuit or detector technologies. In this paper we present the detector models and its achievement through electro-optical measurements and their applications.

A simulator (GSIM) for missile seekers that can be used as a general tool in missile seeker performance analysis has been developed. The simulator contains all the subsystems of a typical missile system and can simulate a missile flight scenario from launch, via target acquisition and tracking, to arrival at the target. GSIM has a fully graphical user interface and runs under Matlab on a regular modern PC. Due to a modular approach, the simulator can easily be upgraded and adapted to different prerequisites. It contains a choice of targets against sky, sea or ground backgrounds. Weather conditions, visibility, and time-of-day are taken into account when seeker images are generated. The effects of detector noise and dome heating are also modeled. The results can be presented as movies from the flight, showing both the seeker image as well as trajectories for the missile and target.

Laser radar (ladar) systems are effective measurement systems with favourite applications like collision control or reconnaissance, etc. A new pixel oriented simulation for scannerless, imaging 3D ladar has been developed. For the first time, any kind of 3D target scenes can be investigated by importing 3D data with the help of VRML. Now, using the simulation, it is possible to easily investigate the influence of laser spot profiles, different target scenes and reflectivities or system configurations. By changing its parameters, the simulation can be adapted to a wide range of systems. Hence, comparison of systems or performance estimation is possible. The simulation proofed as a useful tool for system design, testing of applicability or verification and evaluation of algorithms. The function of the simulation was verified by measurement data. In this paper, the use of simulation is presented. By showing different applications, future development is discussed.

The estimation of the performance of atmospheric electro-optical systems depends on the accuracy of the atmospheric models being used in the propagation prediction codes. On the basis of a large set of imaging LIDAR measurements a Middle East model of refractive turbulence strength (Cn2) vertical profile has been developed. The model is presented in this work, and laser beam wander and widening at different elevation heights in target plane is estimated. Implications can be important for optical communication, laser weaponry, imaging through the atmosphere, and adaptive optics.

Refractive index structure parameter, C²_n, which characterizes turbulence caused by local gradients of microscale meteorological parameters and by variations of macrometeorological features of the atmosphere such as air temperature, wind speed and direction, relative humidity, etc., is examined theoretically and experimentally for near ground Middle East environments. In our theoretical analysis, we present several known models for over-land atmospheric optical communication or imaging channels to predict the turbulence intensity (represented by C²_n). Via comparison with our two-year continuous experiments carried out in Israel we show their limitations for both day- and nighttime turbulent atmospheres under different meteorological conditions. An extension of an existing "practical" model, applicable for two summer and winter seasons, is presented in this work which, as is shown experimentally, can be a good predictor of C²_n for optical atmospheric paths in Middle East climates.

We propose a cost-effective, compact, and robust optoelectronic sensing system for measuring ballistic impact velocity and distribution of the projectile motion. The key elements consisted of this system are four photo-gates hybridized by compound one-dimensional prism array and analog/digital electronic components. The number of light sources and photodetectors used in a photo-gate was reduced to one pair of that. The time interval passing each pair can be measured precisely (~10^-8 s). The average velocity and location of projectile are carried out according the measured time intervals. The system can precisely measure the velocity of a bullet as it leaves a gun barrel and the velocity toward the trajectory outside the firearm. Furthermore, the system uses a commonly found low-powered laser pointer as light source. Compared with other optoelectronic sensing systems that use high-powered lasers, our system is both economical and safe.

In this paper, an innovative grid-based approach to optimize the sensor arrangement in a sensor array is presented. Such an optimized sensor arrangement involving low-cost sensors finds its use in a variety of areas as in automotive safety applications. The potential cost-savings achievable through the use of such sensor systems makes them attractive for car makers. The presented approach is based on an array of N sensors located in a horizontal plane. The sensors that are being used are low-cost infrared sensors, which provide an output voltage depending on the presence of an object inside the sensor's field of view (FOV). Since every sensor has a limited FOV and range-of-sight, several sensors with overlapping FOV's are necessary to cover any specific region of interest (ROI) satisfactorily. The goal of the presented approach is to identify an optimal sensor arrangement for object localization within the ROI. Since only the signal changes are used for processing and not their absolute values, it is imperative that FOV's of at least two sensors should overlap for object position estimation. In addition, the accuracy of the estimation depends on the size of the overlapping area. To solve this (multi-faceted) optimization problem there were no convenient analytic solutions available. Therefore a numerical grid-based solution to compute the best sensor arrangement was developed in this approach. The ROI is represented by a regular grid. Every cell in the grid has a determined weighting function. The formulation of the weighting function is the key to the optimization problem and it is based on the following parameters: number of sensors that cover the cell, dimensions of the overlapping areas and the complete coverage of the ROI. The sum over all cell-weights within the grid is the cost function to be optimized. Due to the high computational effort several algorithms are considered and the final implementation with a simulated annealing approach is chosen because of its ability to find a global minimum in reasonable time.

Despite MTF is widely accepted as the most complete figure of merit describing optical quality of image intensifier tubes(IIs), it is not well-established neither in industrial nor governmental testing laboratories. This work aims to advance in the standardization of MTF testing procedures for modern IIs. A versatile device to measure MTF of IIs, based on different FFT related methods, was successfully developed and tested. Several stimuli (slits, 3 and 15 bar targets, random targets) were integrated in the system. Novel algorithms with adaptive parameter selection were developed for windowing, background thresholding, stimulus tilt correction, focusing, spatio-temporal denoising, normalization and scaling. All the methods used were simulated before measurement implementation. The measurement of the MTF of the system with the different methods provides the same result, validating the methods. Measurements on two reference tubes showed that the MTF is sensitive to image quality differences, even with similar limiting resolution. Gain control, halo and luminance influence need further research. The results reported are useful to advance in finding a definitive standard method for measuring IIs MTF.

Some years ago QinetiQ introduced a short-range reconnaissance unmanned air vehicle (UAV), known as OBSERVER, which carried a visible three-camera sensor. To increase its versatility, a compatible infrared (IR) thermal imaging (TI) sensor was developed for the vehicle for operation in the 8-12mm waveband with a dual field of view function. The sensor incorporates a specially designed camera board, employing two IR lead scandium tantalate (PST) detectors based on UK un-cooled TI technology. Since no cooling engine is required for the detectors, the sensor module is very lightweight and hence well suited to its UAV application. So as to achieve the minimum possible payload for the vehicle, in addition to the lightweight detectors and electronics board, compact low mass optical solutions were devised for the camera objectives. These functioned at a relative aperture of f/1.0 and were designed to provide stable focus and imaging performance over a comparatively large temperature span (-10°C to + 50°C) to enable all weather operation. In order to achieve an athermalisation scheme devoid of elaborate electro-mechanical drives, thermally passive solutions were developed for the objectives in which the differing thermal characteristics of the components were designed to self-cancel optically. In this paper, the design and performance limitations of the optics are discussed and the procedure employed for establishing a thin lens pre-design for one of the objectives is described.

The generalized computer model of electro-optical systems COMOS has been used for the predicting and analyzing the performance of thermal imagers (TI). The identity of calculation and experimental target range performance tests was satisfactorily enough