The growing demand for lower cost infrared sensors and cameras has focused attention on the need for low cost optics for the long wave and mid-wave infrared region. The combination of chalcogenide glasses and Precision Glass Molding (PGM) is the enabling technology for low cost infrared optics. The lack of detailed material properties data has limited its acceptance in the commercial market, but increased demand and recent cost reductions in infrared sensors has focused additional attention onto these materials as a cost driver for infrared systems. This investigation reviews the material performance and repeatability for a number of different chalcogenide glasses. Material properties including composition, glass transition temperature (T_g), coefficient of thermal expansion (CTE), index of refraction, transmission and change in index over temperature (dn/dT) are explored. Specific attention is given toward glasses that achieve high yields during precision glass molding and are candidates for commercial success.

The image quality of today's state-of-the-art IR objective lenses is constantly improving while at the same time the market for thermography and vision grows strongly. Because of increasing demands on the quality of IR optics and increasing production volumes, the standards for image quality testing increase and tests need to be performed in shorter time. Most high-precision MTF testing equipment for the IR spectral bands in use today relies on the scanning slit method that scans a 1D detector over a pattern in the image generated by the lens under test, followed by image analysis to extract performance parameters. The disadvantages of this approach are that it is relatively slow, it requires highly trained operators for aligning the sample and the number of parameters that can be extracted is limited. In this paper we present lessons learned from the R and D process on using focal plane array (FPA) sensors for testing of long-wave IR (LWIR, 8-12 m) optics. Factors that need to be taken into account when switching from scanning slit to FPAs are e.g.: the thermal background from the environment, the low scene contrast in the LWIR, the need for advanced image processing algorithms to pre-process camera images for analysis and camera artifacts. Finally, we discuss 2 measurement systems for LWIR lens characterization that we recently developed with different target applications: 1) A fully automated system suitable for production testing and metrology that uses uncooled microbolometer cameras to automatically measure MTF (on-axis and at several o-axis positions) and parameters like EFL, FFL, autofocus curves, image plane tilt, etc. for LWIR objectives with an EFL between 1 and 12mm. The measurement cycle time for one sample is typically between 6 and 8s. 2) A high-precision research-grade system using again an uncooled LWIR camera as detector, that is very simple to align and operate. A wide range of lens parameters (MTF, EFL, astigmatism, distortion, etc.) can be easily and accurately measured with this system.

Detector arrays using Metal-Organic Vapour Phase Epitaxy (MOVPE) grown HgCdTe (MCT) on GaAs substrates have been in production at SELEX Galileo for over 10 years and are a mature technology for medium wave, long wave, and dual-band tactical applications. The mesa structure used in these arrays is optimised for MTF, quantum efficiency and dark currents. Further development of the technique has migrated to very long wave and short wave bands, mainly for space and astronomy applications, and for mid wave applications towards smaller pixels and higher operating temperatures. The emphasis of this paper is on recent experiments aimed at further improving HOT performance.

This paper describes the recent developments of Mercury Cadmium Telluride (MCT) infrared technologies in France at Sofradir and CEA-LETI made in the frame of the common laboratory named DEFIR. Among these developments, one can find the crystal growth of high quality and large Cadmium Zinc Telluride (CZT) substrates which is one of the fundamental keys for high quality and affordable detectors. These last years, a great effort was done on this topic and also on MCT epilayer process from Short Waves (SW) to Very Long Waves (VLW). These developments about the quality of the material are needed for the challenge of the High Operating Temperature (HOT). Over these lasts years, the operating temperature of n/p MCT detectors was increase of several tens of Kelvin. In addition the development of the p/n MCT technology that reduces dark current by a factor ~100 saves about twenty Kelvin more. The next step for the increase in operating temperature will be the complex photodiodes architectures using molecular beam epilayer. The reduction of the pixel pitches is another challenge for infrared technologies for Small Weight and Power (SWAP) detectors. Moreover, this reduction allows the increase in the resolution and consequently in the detection range of the systems. In addition, last results on 3rd generation detectors such as multicolor focal plan arrays, 2D, 3D, low noise and high images rate focal plane array using Avalanche Photodiose (APD) are described.

Cooled IR technologies are challenged for answering new system needs like compactness and reduction of cryo-power which is key feature for the SWaP (Size, Weight and Power) requirements. 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. Sofradir has improved its HgCdTe technology to open the way for High Operating Temperature systems that release the Stirling cooler engine power consumption. Solutions for high performance detectors such as dual bands, much smaller pixel pitch or megapixels will also be discussed. In the meantime, the development of avalanche photodiodes or TV format with digital interface is key to bringing customers cutting-edge functionalities. Since 1997, Sofradir has been working with Thales and Research Technologies (TRT) to develop and produce Quantum Well Infrared Photodetectors (QWIP) as a complementary offer with MCT, to provide large LW staring arrays. A dualband MW-LW QWIP detector (25μm pitch 384×288 IDDCA) is currently under development. We will present in this paper its latest results.

The high level of accumulated expertise by ULIS and CEA/LETI on uncooled microbolometers made from amorphous silicon enables ULIS to develop ¼ VGA IRFPA formats with 17μm pixel-pitch to enable the development of small power, small weight (SWAP) and high performance IR systems. ROIC architecture will be described where innovations are widely on-chip implemented to enable an easier operation by the user. The detector configuration (integration time, windowing, gain, scanning direction…), is driven by a standard I²C link. Like most of the visible arrays, the detector adopts the HSYNC/VSYNC free-run mode of operation driven with only one master clock (MC) supplied to the ROIC which feeds back pixel, line and frame synchronizations. On-chip PROM memory for customer operational condition storage is available for detector characteristics. Low power consumption has been taken into account and less than 60 mW is possible in analog mode at 60 Hz and < 175 mW in digital mode (14 bits). A wide electrical dynamic range (2.4V) is maintained despite the use of advanced CMOS node. The specific appeal of this unit lies in the high uniformity and easy operation it provides. The reduction of the pixel-pitch turns this TEC-less ¼ VGA array into a product well adapted for high resolution and compact systems. NETD of 35 mK and thermal time constant of 10 ms have been measured leading to 350 mK.ms figure of merit. We insist on NETD trade-off with wide thermal dynamic range, as well as the high characteristics uniformity and pixel operability, achieved thanks to the mastering of the amorphous silicon technology coupled with the ROIC design. This technology node associated with advanced packaging technique, paves the way to compact low power system.

Recent developments at the Infrared Lab (LIR) of CEA, LETI have been concentrated on the pixel size reduction of uncooled infrared detectors. With the support from French company ULIS, we have successfully demonstrated the technological integration of 12μm pixels on a commercial TV-format read-out circuit (VGA-ROIC) supplied by ULIS. The 12μm pixel has been designed, processed and characterized in CEA, LETI and first results showed exceptional performances. This paper presents the characterization and associated imagery results.

Silicon based vacuum packaging is a key enabling technology for achieving affordable uncooled Infrared Focal Plane Arrays (IRFPA) as required by the promising mass market for very low cost IR applications, such as automotive driving assistance, energy loss monitoring in buildings, motion sensors… Among the various approaches studied worldwide, the CEA, LETI is developing a unique technology where each bolometer pixel is sealed under vacuum at the wafer level, using an IR transparent thin film deposition. This technology referred to as PLP (Pixel Level Packaging), leads to an array of hermetic micro-caps each containing a single microbolometer. Since the successful demonstration that the PLP technology, when applied on a single microbolometer pixel, can provide the required vacuum < 10^-3 mbar, the authors have pushed forward the development of the technology on fully operational QVGA readout circuits CMOS base wafers (320 x 240 pixels). In this outlook, the article reports on the electro optical performance obtained from this preliminary PLP based QVGA demonstrator. Apart from the response, noise and NETD distributions, the paper also puts emphasis on additional key features such as thermal time constant, image quality, and ageing properties.

We report on the growth, fabrication and characterization of GaInAsSb p-i-n photodiodes with a high sensitivity in the short-wave infrared. Uniquely these photodiodes are grown on a GaAs substrate using the interfacial misfit array technique, which accommodates the lattice mismatch at an abrupt GaAs/GaSb interface. Top illuminated mesa photodiodes with varying area were fabricated and characterized at room temperature. A zero bias resistance area product of 260 Ωcm² is measured, together with a responsivity of up to 0.8 AW^-1 without an anti-reflection coating. The D* at zero bias is estimated to be 4.5x10¹⁰ Hz^1/2W^-1 which is approaching the best results reported for GaInAsSb photodiodes. Hence this work presents a promising alternative to GaInAsSb detectors grown lattice matched on GaSb substrates, strained InGaAs detectors grown on InP substrates or HgCdTe detectors. Making use of cheaper GaAs substrates, available in larger diameters and dry etch chemistry, the GaInAsSb photodiode technology reported here is particularly well placed to support future lower cost, larger area focal plane arrays approaching gigapixel resolution.

Polarimetric imaging (PI) is of increasing importance in determining additional scene information beyond that of conventional images. For very long-range surveillance, image quality is degraded due to turbulence. Furthermore, the high magnification required to create images with sufficient spatial resolution suitable for object recognition and identification require long focal length optical systems. These are incompatible with the size and weight restrictions for aircraft. Techniques which allow detection and recognition of an object at the single pixel level are therefore likely to provide advance warning of approaching threats or long-range object cueing. PI is a technique that has the potential to detect object signatures at the pixel level. Early attempts to develop PI used rotating polarisers (and spectral filters) which recorded sequential polarized images from which the complete Stokes matrix could be derived. This approach has built-in latency between frames and requires accurate registration of consecutive frames to analyze real-time video of moving objects. Alternatively, multiple optical systems and cameras have been demonstrated to remove latency, but this approach increases cost and bulk of the imaging system. In our investigation we present a simplified imaging system that divides an image into two orthogonal polarimetric components which are then simultaneously projected onto a single detector array. Thus polarimetric data is recorded without latency on a single snapshot. We further show that, for pixel-level objects, the data derived from only two orthogonal states (H and V) is sufficient to increase the probability of detection whilst reducing false alarms compared to conventional unpolarised imaging.

We report a trial wherein a simple 4 CCD visible-band Polarimetric Imaging (PI) camera was fielded against aircraft debris distributed across an arid terrain, a littoral region and a small number of maritime debris targets A debris field realistically simulating an aircrash and a debris grid of aircraft remains were observed from an air platform flying in dry and sunny conditions. We report PI utility in support of air accident investigation by an enhanced ability to successfully locate small targets within the scene via the use of colour enhanced and decorrelated intensity PI products. Our results indicate that handheld PI capability may represent an effective low cost, upgrade and augmentation option for existing and future imaging systems that would support air accident investigators and assist in the cueing of more sophisticated assets and/or analyst attention.

Various visible and infrared cameras have been tested for the early detection of wildfires to protect archeological treasures. This analysis was possible thanks to the EU Firesense project (FP7-244088). Although visible cameras are low cost and give good results during daytime for smoke detection, they fall short under bad visibility conditions. In order to improve the fire detection probability and reduce the false alarms, several infrared bands are tested ranging from the NIR to the LWIR. The SWIR and the LWIR band are helpful to locate the fire through smoke if there is a direct Line Of Sight. The Emphasis is also put on the physical and the electro-optical system modeling for forest fire detection at short and longer ranges. The fusion in three bands (Visible, SWIR, LWIR) is discussed at the pixel level for image enhancement and for fire detection.

Saudi Arabia has borders covering over 4,300 km that are shared with seven countries. Such large borders pose many challenges for security and patrol. Thermal imagers are considered the most reliable means of threat detection, however, they are quite costly, which can prevent using them over large areas. This work discusses a multi-sensor acoustic and optical implementation for threat detection as an effort to reduce system cost. The acoustic sensor provides position and direction recognition by using a four microphone setup. The data analysis of field tests will be discussed in this work.

The evolution of infrared imaging technology has always followed, from a distance, the evolution of the technology in the visible waveband with ever increasing resolutions and decreasing pixel pitch. With such evolution the cameras in the visible are smaller than ever and display high quality imaging. Nowadays the size of the pixels in the infrared is generally much larger than its counterpart in the visible. However, the ratio of the size of the pixel to the wavelength is much smaller in the infrared than in the visible with the consequence that the gain on the pixel size could be limited considering today's rules of design. In the infrared, the recent advent of large 1024 x 768 pixel focal plane arrays based on 17 um pixel for the 8 to 12 um waveband raises development challenges. Nevertheless, it was recently shown that sampling a scene at a frequency higher than the one corresponding to the pixel pitch is an efficient way of increasing the resolution of an image for given pixel size and FPA dimensions. Following this strategy a 2048 x 1536 pixel imager with integrated microscan was developed based on an uncooled bolometer FPA. Due to its very small 8.5 um efficient pixel pitch the imager offers very high resolution and large field-of-view (FOV) using a short 50 mm focal length. Furthermore, since the size of the FPA is maintained at a reasonable size and the pixel pitch is very small the optics is compact and lightweight and the level of aberrations at the larger angles of the FOV is kept to a minimum offering excellent imaging quality. Such a platform could thus be used for very compact surveillance system and remote sensing instrumentation. This paper reviews the optics developed to perform the microscanned acquisition, the acquisition electronics and presents examples of high-resolution imaging. Finally, comparison of imaging with and without microscan is provided illustrating the usefulness of the microscan system despite the fact that the efficient pixel pitch is very close to the lower limit of the 8 to 12 um infrared waveband.

The detection and tracking of ballistic missiles (BMs) during launch or cloud break using satellite based electro-optical (EO) sensors is a promising possibility for pre-instructing early warning and fire control radars. However, the successful detection of a BM is depending on the applied infrared (IR)-channel, as emission and reflection of threat and background vary in different spectral (IR-) bands and for different observation scenarios. In addition, the spatial resolution of the satellite based system also conditions the signal-to-clutter-ratio (SCR) and therefore the predictability of the flight path. Generally available satellite images provide data in spectral bands, which are suitable for remote sensing applications and earth surface observations. However, in the fields of BM early warning, these bands are not of interest making the simulation of background data essential. The paper focuses on the analysis of IR-bands suitable for missile detection by trading off the suppression of background signature against threat signal strength. This comprises a radiometric overview of the background radiation in different spectral bands for different climates and seasons as well as for various cloud types and covers. A brief investigation of the BM signature and its trajectory within a threat scenario is presented. Moreover, the influence on the SCR caused by different observation scenarios and varying spatial resolution are pointed out. The paper also introduces the software used for simulating natural background spectral radiance images, MATISSE (“Advanced Modeling of the Earth for Environment and Scenes Simulation”) by ONERA [1].

Supplying thermal imagers for today's operational needs requires flexibility, responsiveness and ever reducing costs. This paper will use the latest thermal imager development in the Catherine range from Thales UK to address the technical interactions with such issues as modularity, re-use, regions of deployment and supply chain management. All this is in the context of the increasingly public operations and the pressures on validating performance especially when weapon aiming is involved.

A main criterion for comparison and selection of thermal imagers for military applications is their nominal range performance. This nominal range performance is calculated for a defined task and standardized target and environmental conditions. The only standardization available to date is STANAG 4347. The target defined there is based on a main battle tank in front view. Because of modified military requirements, this target is no longer up-to-date. Today, different topics of interest are of interest, especially differentiation between friend and foe and identification of humans. There is no direct way to differentiate between friend and foe in asymmetric scenarios, but one clue can be that someone is carrying a weapon. This clue can be transformed in the observer tasks detection: a person is carrying or is not carrying an object, recognition: the object is a long / medium / short range weapon or civil equipment and identification: the object can be named (e. g. AK-47, M-4, G36, RPG7, Axe, Shovel etc.). These tasks can be assessed experimentally and from the results of such an assessment, a standard target for handheld objects may be derived. For a first assessment, a human carrying 13 different handheld objects in front of his chest was recorded at four different ranges with an IR-dual-band camera. From the recorded data, a perception experiment was prepared. It was conducted with 17 observers in a 13-alternative forced choice, unlimited observation time arrangement. The results of the test together with Minimum Temperature Difference Perceived measurements of the camera and temperature difference and critical dimension derived from the recorded imagery allowed defining a first standard target according to the above tasks. This standard target consist of 2.5 / 3.5 / 5 DRI line pairs on target, 0.24 m critical size and 1 K temperature difference. The values are preliminary and have to be refined in the future. Necessary are different aspect angles, different carriage and movement.

The progress in laser technology leads to very compact but nevertheless powerful laser sources. In the visible and near infrared spectral region, lasers of any wavelength can be purchased. Especially continuous wave laser sources pose a serious threat to the human eye and electro-optical sensors due to their high proliferation and easy availability. The manifold of wavelengths cannot be encountered by conventional safety measures like absorption or interference filters. We present a protection concept for electro-optical sensors to suppress dazzling in the visible spectral region. The key element of the concept is the use of a digital micromirror device (DMD) in combination with wavelength multiplexing. This approach allows selective spectral filtering in defined regions of interest in the scene. The system offers the possibility of automatic attenuation of dazzling laser radiation. An anti-dazzle algorithm comprises the analysis of the laser wavelength and the subsequent activation of the appropriate micromirrors of the DMD.

Results are presented for generation of 1064 nm and 1573 nm outputs using a common ring resonator for a laser diodeside-pumped zig-zag geometry Nd:YAG laser slab and three NCPM (non-critically phase-matched) KTP crystals. The performance of the resonator at each wavelength is reported, for various configurations. First a common resonator was tested, then a separate resonator was used to gain an understanding of the performance variation with resonator length and OPO output coupling. A second common resonator was then tested, which had an optimized configuration to improve its efficiency. The conversion efficiency of the final design was 35% with 29 mJ output at 1573 nm wavelength for 83 mJ at 1064 nm.

We report on the development and characteristics of athermal diode-pumped designator modules as Original Equipment Manufacturer (OEM) for targeting application. These modules are designed with the latest diode-pumped technology minimizing volume and power consumption. The core technology allows to address multi-platforms requirements such as land or airborne. Products are composed of a Laser Transmitter Unit (LTU) and Laser Electronic Unit (LEU) for modular approach.

Thermography is one of many techniques used for nondestructive testing for which both passive and active approach could be taken. The passive approach is effective for materials and structures which are naturally at a different temperature than the environment. The active approach requires an external heating source to stimulate the materials or structures to be tested. These methods can be also applied to detect mines hidden in the ground. Passive approach is used when natural heating of soil by sun radiation is exploited. In the case of active approach it is used an external heating source for example a microwave source to provide thermal stimulation. In this paper the results of our experiments with both methods carried out in the laboratory set-up and in the outdoor measuring field are presented.

The growing interest for fast, compact and cost-effective 3D ranging imagers for automotive applications has prompted to explore many different techniques for 3D imaging and to develop new system for this propose. CMOS imagers that exploit phase-resolved techniques provide accurate 3D ranging with no complex optics and are rugged and costeffective. Phase-resolved techniques indirectly measure the round-trip return of the light emitted by a laser and backscattered from a distant target, computing the phase delay between the modulated light and the detected signal. Singlephoton detectors, with their high sensitivity, allow to actively illuminate the scene with a low power excitation (less than 10W with diffused daylight illumination). We report on a 4x4 array of CMOS SPAD (Single Photon Avalanche Diodes) designed in a high-voltage 0.35 μm CMOS technology, for pulsed modulation, in which each pixel computes the phase difference between the laser and the reflected pulse. Each pixel comprises a high-performance 30 μm diameter SPAD, an analog quenching circuit, two 9 bit up-down counters and memories to store data during the readout. The first counter counts the photons detected by the SPAD in a time window synchronous with the laser pulse and integrates the whole echoed signal. The second counter accumulates the number of photon detected in a window shifted with respect to the laser pulse, and acquires only a portion of the reflected signal. The array is readout with a global shutter architecture, using a 100 MHz clock; the maximal frame rate is 3 Mframe/s.

The utility of military lasers, particularly in the area of laser designation for laser-guided weapons, is well understood. Laser systems based on Nd:YAG have been fielded since the 1980’s and over the last three decades have introduced incremental technology steps to improve performance and weight. The most recent technology step has been the introduction of athermal lasers based on laser-diode pumping of Nd:YAG and products are now emerging for use on the battlefield. The technical performance, efficiency, size, weight and power for these lasers, has been key to driving the new production designs. In this paper, we review the development of the laser designs and their introduction since the advent of laser designation. In particular, we compare the relative performance and characteristics over the evolution of fielded laser designators. Moreover, we will review the key building blocks for the design of athermal lasers and describe some critical design issues for engineering and productionisation of a military laser system, including removal of thermal lensing, novel diode-pumping schemes and robustness over the environment. These will be exemplified using results from the development of the SELEX Galileo Type 163 Laser Target Designators. These will cover not only technical performance, power and efficiency, but also thermal management, mass, volume, cost and overall complexity for manufacture.

Modern InfraRed (IR) cameras have High Dynamic Range (HDR) and excellent sensitivity. They collect images using a number of bits much higher than the 8-bits used in displays or than those effectively perceived by the human visual system. In IR imagery, suitable techniques to display HDR images are therefore required in order to improve the visibility of the details while preserving the global perception of the scene. Visualization of HDR images has already been widely studied for visible-light images. In the IR framework only a few works have been proposed which tightly depend on the operating scenario and on the application of interest. In most cases such works have been obtained by modifications of methods proposed for visible light images rather than by developing visualization techniques taking into account the specific mechanism of IR image formation. In the literature, the techniques developed to display HDR images are mainly based on two approaches: contrast enhancement (CE)-oriented techniques and dynamic range compression (DRC)-oriented techniques. The former operate on image contrast to increase the perceptibility of details. The latter reduce the signal dynamic thus attenuating the large-scale intensity changes that do not contain relevant information. In addition, some of the proposed methods for HDR take advantage of both the approaches. In this work, a DRC approach is considered for visualization of HDR-IR images of maritime scenarios. A new method is presented that exploits clustering information and maps the output image according to the information content of each cluster by means of a suitable weighting function. The effectiveness of the presented technique is analyzed using IR images of a maritime scenario acquired in two different case studies. Moreover, the output images obtained with the proposed method are compared with those given by techniques previously proposed for visualization of IR images. The results show the effectiveness of the proposed technique in terms of details enhancement, robustness against the horizon effect and presence of very warm objects.

IR-sensors are mainly utilized in video surveillance systems in order to provide vision during nighttime and in diffuse lighting conditions. The dynamic range of IR-sensors usually exceeds that of conventional display devices. Hence, range compression associated with loss of information is always required. Range compression methods can be divided into global methods, which are based on the intensity distribution, and local methods focused on smaller regions of interest. In contrast to local methods, global methods are computationally efficient. Nevertheless, global methods have the drawback that fine details can be suppressed by intensity changes at image locations which are unrelated to the object of interest. In order to overcome these restrictions, we propose a method to render IR images based on high level object information. The overall processing pipeline consists of a contrast enhancement method, followed by object detection, and a range compression method that takes the location of objects into account. Here we use pedestrians as an exemplary object category. The output of the detector is a rectangular bounding box, centered at the person location. Restricting range compression to a person location, allows to display details on the person surface that most probably would remain undetected using global range compression methods. The proposed combination of rendering with high level information is intended to be integrated in a surveillance system to assist human operators. Towards this end, this paper provides some insights into the design of visualization tools.

This paper presents a digital hardware filter that estimates the nonuniformity (NU) noise in an Infrared Focal Plane Array (IRFPA) and corrects it in real time. Implementing the algorithm in hardware results in a fast, compact, low-power nonuniformity correction (NUC) system that can be embedded into an intelligent imager at a very low cost. Because it does not use an external reference, our NUC circuit works in real time during normal operation, and can track parameter drift over time. Our NUC system models NU noise as a spatially regular source of additive noise, uses a Kalman filter to estimate the offset in each detector of the array and applies an inverse model to recover the original information captured by the detector. The NUC board uses a low-cost Xilinx Spartan 3E XC3S500E FPGA operating at 75MHz. The NUC circuit consumes 17.3mW of dynamic power and uses only 10% of the logic resources of the FPGA. Despite ignoring the multiplicative effects of nonuniformity, our NUC circuit reaches a Peak Signal-to-Noise Ratio (PSNR) of 35dB in under 50 frames, referenced to two-point calibration using black bodies. This performance lies within 0.35dB of a double-precision Matlab implementation of the algorithm. Without the bandwidth limitations currently imposed by the external RAM that stores the offset estimations, our circuit can correct 320x240-pixel video at up to 1,254 frames per second.

The digital image processing of uncooled LWIR thermal detectors is one of the main steps in the research and development of thermal cameras. The study of this technology is a strategic issue for military and civil areas, considering that thermal imaging equipment have dual application. This paper aims to design and develop a pipeline of all processing steps required to obtain high performance images with low noise and high contrast. In addition to the digital processing algorithms, this paper presents some results of electro-optical characterization on the assembled system, indicating the main figures of merit that guide the study of this technology.

This paper deals with point target detection in non-stationary background such as cloud scenes in aerial or satellite imaging. We propose a new method to estimate second order background statistics within a spatial detection method by Matched Filter (MF). Our approach consists in classifying the pixels of the image by gathering the pixels of similar covariance matrices and in estimating one covariance matrix for each class. We use a Classification Expectation-Maximization (CEM) algorithm based on a zero mean Gaussian mixture model. A key issue is the robustness of the classification with regard to target presence. This problem is efficiently tackled in a very simple manner. The resulting Gaussian Mixture Matched Filter (GMMF) has the advantage to adapt itself to second order non-stationary backgrounds and requires only the tuning of the window size used to build the observation vector associated with each pixel. Efficiency of the proposed GMMF approach is demonstrated on a large variety of cloudy sky backgrounds.

A modular vehicle detection system, using a two-stage hypothesis generation (HG) and hypothesis combination (HC) approach is presented. The HG stage consists of a set of simple algorithms which parse multi-modal data and provide a set of possible vehicle locations. These hypotheses are subsequently fused in a combination stage. This modular design allows the system to utilise additional modalities where available, and the combination of multiple information sources is shown to reduce false positive detections. The system uses Thales' high-resolution long wave infrared polarimeter and a four-band visible/near infrared multispectral system. Vehicle cues are taken from motion ow vectors, thermal intensity hot spots, and regions with a locally high degree of linear polarisation. Results using image sequences gathered from a moving vehicle are shown, and the performance of the system is assessed with Receiver Operator Characteristics.

Automatic detection and tracking of objects get more important with the increasing number of surveillance cameras and mobile platforms having cameras. Tracking systems are either designed with stationary camera or designed to work in moving camera. When the camera is stationary, correspondence based tracking with background subtraction has a number of benefits such as enabling automatic detection of new objects in the scene and better tracking accuracy. On the other hand, mean shift is a histogram-based tracking method which is suitable for tracking objects under unconstrained scenarios like moving camera. However, with mean shift, the objects to be tracked cannot be detected automatically, only existing or manually selected objects can be tracked. In this paper, we propose a dual-mode system which combines the advantages of correspondence based tracking and mean shift tracking. A reliability measure based on background update rate is calculated for each frame. Under normal operating conditions, when the background estimation is working reliably, correspondence based tracking is used. When the reliability of background estimation becomes low, due to moving camera, the system automatically switches to mean shift tracking until the reliability of background information increases again. The results show that the system can detect new objects and track them reliably using background subtraction. Even though the background subtraction based systems detect high number of false objects when the camera starts moving, the proposed system hands over the tracked objects to mean shift tracker and avoids detection of false objects and enables uninterrupted tracking.

In a previous paper we have presented the design and the expected performance of the latest generation of visible/infrared spectroradiometric system for field use, called SR 5000N. Examples of significantly advanced performance are expected in compactness, field of view response uniformity, measurement speed, ease of pointing the Line of Sight (LOS) on the object to be measured, and interchangeability of configuration modules, such as fields of view size, wavelength range and detectors. One unique and advanced feature of this system is that a Visible/Near IR spectrometer is incorporated in the system to provide, together with the IR optical channel, a simultaneous measurement of the same object in the whole 0.2 to 14.5 microns spectral range. In this paper we present the actual system after being built and some performance results on field of view uniformity and symmetry. Unfortunately, due to delays in R and D schedule, not all features have been completed so far and therefore not all results can be shown here as we initially planned.

Additional performance results will be reported in a future paper, as soon as the system development and characterization will be completed.

The Imaging Fourier Transform Spectrometer (IFTS) is the temporal modulated Michelson interferometer in which a single-element detector is replaced by an area focal plane arrays. Each pixel of detector arrays records observed area radiation and then yield the corresponding spectrum by Fourier transforms. While, area focal plane arrays improve spatial resolution and expand area coverage. However, this innovation technology has many technical challenges to be overcome. In this paper, the challenges caused by area focal plane arrays are discussed. The simulations of interference modulation (IM) of Fourier transform spectral imaging are presented. The IM changes as the extensions of pixel are simulated and analyzed. And a phenomenon that interference modulation deteriorates with spectral resolution improvement is discussed. The results show that, the off-axis pixels are sampled at slightly shorter OPDs, compared with the pixel in the center. The decrease of interference modulation caused by area focal plane arrays is related to both the position of each pixel and maximum optical path difference. Interference modulation decline in the format of a quadratic function as the pixel position extends. And this decrease in short waveband is more significant than that in long waveband. It is noticed that there is a key spectral resolution for IFTS interference modulation. When the spectral resolution is set below the key point, the IM decrease smoothly and slowly at the high level. However, if the spectral resolution keeps improving over the key point, the modulation will decline abruptly.

The multispectral imaging equipment is a kind of new generation remote sensor, which can obtain the target image and the spectra information simultaneously. A digital airborne multispectral camera system using discrete filter method had been designed and implemented for unmanned aerial vehicle (UAV) and manned aircraft platforms. The digital airborne multispectral camera system has the advantages of larger frame, higher resolution, panchromatic and multispectral imaging. It also has great potential applications in the fields of environmental and agricultural monitoring and target detection and discrimination. In order to enhance the measurement precision and accuracy of position and orientation, Inertial Measurement Unit (IMU) is integrated in the digital airborne multispectral camera. Meanwhile, the Temperature Control Unit (TCU) guarantees that the camera can operate in the normal state in different altitudes to avoid the window fogging and frosting which will degrade the imaging quality greatly. Finally, Flying experiments were conducted to demonstrate the functionality and performance of the digital airborne multispectral camera. The resolution capability, positioning accuracy and classification and recognition ability were validated.

Technology of infrared (IR) avalanche photodiodes (APDs) gradually moves from simple single element APD to 2D focal plane arrays (FPA). Spectral covering of APDs is expanded continuously from classic 1.3 μm to longer wavelengths due to using of narrow-gap semiconductor materials like Hg_1-xCd_xTe. APDs are of great interest to developers and manufacturers of different optical communication, measuring and 3D reconstruction thermal imaging systems. Major IR detector materials for manufacturing of high-performance APDs became heteroepitaxial structures In_xGa_1-xAs_yP_1-y and Hg_1-xCd_xTe. Progress in IR APD technology was achieved through serious improvement in material growing techniques enabling forming of multilayer heterostuctures with separate absorption and multiplication regions (SAM). Today SAM-APD design can be implemented both on In_xGa_1-xAs_yP_1-y and Hg_1-xCd_xTe multilayer heteroepitaxial structures. To create the best performance optimal design avalanche heterophotodiode (AHPD) it is necessary to carry out a detailed theoretical analysis of basic features of generation, avalanche breakdown and multiplication of charge carriers in proper heterostructure. Optimization of AHPD properties requires comprehensive estimation of AHPD’s pixel performance depending on pixel’s multi-layer structure design, layers doping, distribution of electric field in the structure and operating temperature. Objective of the present article is to compare some features of 1.55 μm SAM-AHPDs based on In_xGa_1-xAs_yP_1-y and Hg_1-xCd_xTe.

Range parameters of observation devices can be determined on the basis of numerical simulations (NVTherm) or on the basis of measured characteristics. Those measurements can be conducted in both laboratory and field conditions. It is, however, difficult to carry on reliable field measurements of range parameters because they are strongly depended on atmospheric conditions. Thus the laboratory measurements are more favorable option. Analysis of literature and catalogue specifications reveal, that range parameters are given mainly on the basis of Johnson criteria or TTP model. The Johnson criteria has been used since the 50s and most of catalogue range specifications are determined according to it. There are also NATO standards, which describe the measurement procedures and methodology required to define the detection, recognition and identification ranges for standard NATO targets. For the determination of range parameters the following device characteristics must be known: minimal resolvable temperature for thermal imaging devices and minimal resolvable contrast for VIS devices. The TTP model offers a new approach to the determination of range characteristics of observation devices. It has been developed by U.S. Army’s Night Vision and Electronic Sensors Directorate since the year 2000. It was created because the modified Johnson criteria did not yield reliable results in case of modern systems with digital image processing. In order to determine the range parameters using TTP model, the modulation transfer function MTF, presample MTF function, and 3D noise of a tested system must be known as well as its basic design data as optical magnification and display type. The paper describes the measurement stand, measurement methodology and the procedure for the determination of range parameters. The results for thermal and VIS cameras are also presented, and they are analyzed and compared with the results obtained from current methods, including the measurement uncertainty figures. Some suggestions on the methodology of measurements are also given.

In recent years, the archaeological tourism has rapidly been developed all over the world, and it has become more and more popular. However, the scope of the human activities has been restricted by complicated geographical terrain, and the popularization of archaeological tourism has been hampered. For the purpose of solving the above problem, the archaeological tourism system of the panoramic dynamic data acquisition system based on unmanned helicopter is designed, and we got the image of the Chinese Ming Dynasty Great Wall realtime 360˚ panoramic dynamic monitor. The applying of this system will increase the scope of the archaeological tourism activities.

The interpretation of IR images depends on radiative properties of observed objects and surrounding scenery. Skills and experience of an observer itself are also of great importance. The solution to improve the effectiveness of observation is utilization of algorithm of image enhancing capable to improve the image quality and the same effectiveness of object detection. The paper presents results of testing the hardware implementation of IR image enhancing algorithm based on histogram processing. Main issue in hardware implementation of complex procedures for image enhancing algorithms is high computational cost. As a result implementation of complex algorithms using general purpose processors and software usually does not bring satisfactory results. Because of high efficiency requirements and the need of parallel operation, the ALTERA’s EP2C35F672 FPGA device was used. It provides sufficient processing speed combined with relatively low power consumption. A digital image processing and control module was designed and constructed around two main integrated circuits: a FPGA device and a microcontroller. Programmable FPGA device performs image data processing operations which requires considerable computing power. It also generates the control signals for array readout, performs NUC correction and bad pixel mapping, generates the control signals for display module and finally executes complex image processing algorithms. Implemented adaptive algorithm is based on plateau histogram equalization. Tests were performed on real IR images of different types of objects registered in different spectral bands. The simulations and laboratory experiments proved the correct operation of the designed system in executing the sophisticated image enhancement.

The designed Infra-red optical system with multi-magnification shows non-uniform thermal distribution only in Wide FOV and suspected to be narcissus effect. To analyze the system’s artifacts more effectively, the optical system design was imported to analysis codes. Initial ray tracing was performed with a point source from the detector to identify main candidates of Narcissus effect by analyzing irradiance distribution and flux distribution. As a second step, a planer source was created at the detector and traced again. As a result, four major candidates were selected and the major contributor was identified among them. To confirm the result with experiment, replacement optical component was manufactured. We can confirm that the Narcissus effect was improved significantly by replacing the identified component.

Non-destructive testing of composite materials is a key technology issue in equipment testing. Among the emerging new testing methods, Lamb-wave technology is getting more and more attention. This paper proposed a sensing method to acquire the Lamb-wave signal in thin plate based on optical low-coherence principles. Methods to acquire Lamb-wave in thin plate using optical low-coherence technology were analyzed, and the technical path of non-contact, high-precision method was chosen. Complete in-line experimental system and methods were designed and built up for testing. A sensor system based on Michelson low-coherence interferometer was set up. The distributed optical fiber sensors were arranged on the top of sample materials for signal detection. Mirrors to enhance reflection intensity were attached on the sample. The phase of sensing arm was modulated by PZT vibration. Then signals were detected and processed by Daubechies10 wavelet and Gabor wavelet. In-line testing of thin plate with features of high-precision and high signal-noise-ratio was realized, which is meaningful to dynamic testing of large-scale structure.

Contemporary infrared detector arrays suffers from technological imprecision which causes that the response to uniform radiation results in nonuniform image with superimposed fixed pattern noise (FPN). In order to compensate this noise there is a need to evaluate detectors characteristics like responsivity and offset of every detector in array. In article the method of determining the responsivity of detectors in a microbolometer array is described. In the method geometrical and optical parameters of the detector array and the measurement system are taken into account. A special test bench was constructed and is consisting of: two precise surface black bodies, aperture limiter, an electronic interface for data acquisition and software for measurement and correction of results with optical parameters of the measuring stand taken into account. Constructed aperture limiter enables evaluation of optical paths in measurement stand with equivalent relative aperture F# from 0.5 to 16.1 In order to evaluate the impact of optical path to radiation distribution in the measurement system, special radiation model was elaborated and evaluated in Zemax software. Incident radiation intensity distribution on the detector surface was calculated using Monte-Carlo method for various parameters of the optical path in the measurement system. Calculated radiation maps were used to compensate radiation intensity nonuniformity of optical measurement system giving more precise responsivity evaluation of detector array parameters. The obtained values of voltage responsivity of the detectors in the array, can be used in algorithms like nonuniformity correction and radiometric calibration of the infrared camera. In article results of responsivity evaluation is presented for microbolometer infrared arrays from ULIS company (France).

Thermal imagers and used therein infrared array sensors are subject to calibration procedure and evaluation of their voltage sensitivity on incident radiation during manufacturing process. The calibration procedure is especially important in so-called radiometric cameras, where accurate radiometric quantities, given in physical units, are of concern. Even though non-radiometric cameras are not expected to stand up to such elevated standards, it is still important, that the image faithfully represents temperature variations across the scene. The detectors used in thermal camera are illuminated by infrared radiation transmitted through a specialized optical system. Each optical system used influences irradiation distribution across an sensor array. In the article a model describing irradiation distribution across an array sensor working with an optical system used in the calibration set-up has been proposed. In the said method optical and geometrical considerations of the array set-up have been taken into account. By means of Monte-Carlo simulation, large number of rays has been traced to the sensor plane, what allowed to determine the irradiation distribution across the image plane for different aperture limiting configurations. Simulated results have been confronted with proposed analytical expression. Presented radiometric model allows fast and accurate non-uniformity correction to be carried out.

In this paper, some basic principles and the implementing flow charts of a series of algorithms for target tracking are described. On the foundation of above works, a moving target tracking software base on the OpenCV is developed by the software developing platform MFC. Three kinds of tracking algorithms are integrated in this software. These two tracking algorithms are Kalman Filter tracking method and Camshift tracking method. In order to explain the software clearly, the framework and the function are described in this paper. At last, the implementing processes and results are analyzed, and those algorithms for tracking targets are evaluated from the two aspects of subjective and objective. This paper is very significant in the application of the infrared target tracking technology.

In this work, PbS colloidal quantum dot based photodiodes are realized that is compatible for integration to read out electronics. Schottky photodiode topology is selected to implement PbS quantum dots as photodetector because of its fast response and moderate sensitivity. The device is formed from Indium tin oxide (ITO) anode, the photosensitive PbS layer and a schottky contact formed of both aluminum or titanium and gold stack. Ligand exchange processes optimized in order to replace long capping ligands of PbS QDs with shorter ones. Layer by layer deposition method is applied to form pinhole free PbS CQD films. For Al/PbS samples rectification ratios greater than 100 is achieved for ±2 V bias voltages. At 2V reverse bias and under 5mW/cm² illumination, 0.195 A/W responsivity and 8.19 x 10¹⁰ Jones normalized detectivity is achieved. For Ti-Au/PbS samples, rectification ratio greater than 250 is achieved for ±2 V bias voltages. At 3V reverse bias, 0.667 A/W responsivity, 53.3 % quantum efficiency and 2,12 x 10¹⁰ Jones normalized detectivity is achieved.