Time-correlated single-photon counting techniques have been applied to time-of-flight ranging and imaging. This paper will describes recent progress in photon-counting systems performing surface mapping of non-cooperative targets. This includes systems designed for short ranges of the order of 1-50 meters, as well as measurements on distributed targets at longer ranges of the order of 100 meters up to ten kilometers. We describe the measurement approach, techniques used for scanning, as well as the signal analysis methodology and algorithm selection. The technique is fundamentally flexible: the trade-off between the integrated number of counts against range repeatability, or depth resolution allows its application in a number of diverse fields. The inherent time gating of the technique, allied to the spatial filtering provided by small active area single-photon detectors, can lead to operation under high ambient light conditions even with low average optical power pulsed sources. We have demonstrated three-dimensional imaging of meter-dimensioned objects where reverse engineering methods using cooperative targets cannot be routinely employed: e.g. mechanically delicate objects, or objects with more than one reflective surface. Using more advanced signal processing algorithms, we have been able to improve the system performance markedly, as measured by the depth resolution at short and long ranges. Furthermore, the application of these methodologies has allowed us to characterize the positions and amplitudes of multiple returns. Hence, the approach can be used for characterization of distributed non-cooperative targets at kilometer ranges, even in environments where low-light level and and/or eye-safe operation is necessary.

The IR-Dual-Band-Camera demonstrator collects simultaneously infrared data in the 3-5 μm (mid-wave infrared, MWIR) and 8-12 μm (long-wave infrared, LWIR) atmospheric windows. The demonstrator is based on a two-layer QWIP focal plane array with 384 x 288 x 2 detector elements. Images are typically acquired with a frame rate of 100 Hz at 6.8 ms integration time and are stored as 14-bit digital data. Two different IR-Dual-Band-Optics were designed and developed: first an 86 mm and 390 mm focal length, F/2 dual field of view optics based on refractive and reflective components and second a pure refractive 100 mm focal length, F/1.5 optics. We present the performance of this IR-Dual- Band-Camera and demonstrate fusion techniques to the pixel-registered dual-band images which show in laboratory tests and field trials promising results with respect to image improvement.

Spectral imagers rely mainly on two techniques for collection of spectral information: gratings and interferometers. The former type needs cooling of the optics to avoid background signals which significantly limit the dynamic range of the measurement. The latter type, in its present commercial configurations, is not suitable for pushbroom operation in an airborne situation. A recent spectral imager configuration based on a shearing interferometer has been shown to be suitable for pushbroom operation without the need for cooling the optics. In this paper we describe the planned implementation of such a spectral imager for the 3-5 μ range, where the interferometer is a specially designed single prism. The advantages of this interferometer configuration are: i) compact optics, ii) high S/N ratio in the 3-5 μ range with small optical collection diameter, and iii) enhanced mechanical stability. The instrument yields a spectrum for 320x240 pixels of the image with a spectral resolution of better than 50 cm^-1. The spectrum is calibrated in units of Watt/(steradian.cm².cm^-1). If used in an airborne pushbroom mode it provides a swath width of 240 pixels in a ~6.9 degree transverse field of view. If used in a horizon scanning configuration, it has a vertical field of ~6.9° and a horizontal field up to 300 degrees. The IFOV is 0.5 milliradians. In this paper the major instrument design considerations are presented. The instrument is being constructed and we will give more details on actual performance and examples of measurement results in a future paper, as we gain more experience. An 8-12 μ range version is also planned for the near future.

We describe a compact mid-infrared active spectroscopic imaging system for the rapid, stand-off detection of gas / chemical agents. Based upon the back-scatter absorption gas imaging (BAGI) technique, the system utilises a miniaturised, extremely efficient all solid state intracavity optical parametric oscillator (OPO) as the imaging illumination source. The OPO produces up to 250mW of tunable radiation in the signal and idler fields over the range 1.3-4.5μm, for a diode pump power of only 3W. Due to the nature of the nonlinear crystal employed within the OPO, the system can be tuned across its spectral range in ~1 second. We obviate the very high cost and complexity of a cooled MCT or InSb video array by raster-scanning the collimated illumination beam over the area of interest and reconstructing the image by sampling the back-scattered radiation with a single element MCT photo-detector at each pixel point. This approach also improves the ultimate signal to noise ratio. Video-like frame rates of 10 f.p.s. have been demonstrated via this technique. The range limit of the instrument is currently <10 meters which is limited by the detector we currently employ. We demonstrate how the system has been used to detect, in real time, leaks of multi-species hydrocarbon gases.

The development of a compact and high performance MWIR step zoom camera based on the 640x480 staring focal plane array (FPA) is described. The camera has a 20 magnification step zoom ranging between 24°x20° for the wide field of view up to 1.2° x 1° for the narrow field of view and an aperture of F#4. The processing electronics is based on a flexible and expandable architecture. Special emphasis is spent on the solutions adopted for the design of this high zoom ratio and fast optics FLIR and on the electronic architecture and algorithms for image processing. An overview of the performance is given.

In the framework of a modernization program, supported by Italian Army, Galileo Avionica (a Finmeccanica company) has developed a family of small equipments based on suites of electro-optics sensors. These modules, designed and built by GA, range from uncooled V0x 25 micron thermal imagers, small and very compact laser rangefinders, CMOS Visible sensors to the last generation of colour OLED microdisplay based visual units. All the EO assemblies are integrated to form very small and lightweight Integrated Sight, a Multi Function Target Locator, and Dynamic Aiming System. Even if the equipments have been developed for military applications many other applications such as law enforcements or surveillance can be envisaged.

High quality night vision digital video is nowadays required for many observation, surveillance and targeting applications, including several of the current soldier modernization programs. We present the performance increase that is obtained when combining a state-of-the-art image intensifier with a low power consumption CMOS image sensor. Based on the content of the video signal, the gating and gain of the image intensifier are optimized for best SNR. The options of the interface with a separate laser in the application for range gated imaging are discussed.

Imaging devices are very attractive as sensors in modern airborne platforms and there is a continuing trend toward widespread employment of imaging either alone or in combination with complementary technologies. In the civil domain, modern silicon CCD and CMOS image sensors are becoming extremely small, so that the package size of commercial miniature cameras is increasingly being dominated by the image forming optics, even if the latter is only a structure supporting a pinhole. Recently, there have been demonstrations of ultra-flat, extremely light weight sensors working in the visible region of the spectrum. Similar ideas for cameras developed to operate in the infra-red could help to drastically reduce the size, weight and cooling requirements of imaging, also offering substantial cost reductions. In addition, designs providing wide field-of-view can potentially eliminate the need for sightline steering hardware. This paper describes work on a biologically inspired imaging system offering a wide field of view, thanks to the use of a multi-aperture sensor based on micro-optics which can be used to observe simultaneously in different directions. Results from a near-infrared, narrowband demonstrator are reported.

This paper at hand describes in details the work that has been carried out for fusing a commercial micro mirror sampling element with TOF acquisition methods and known Hadamard multiplexing techniques for implementation of fast and SNR optimized 3D image capture. The theoretical basics of TOF and Hadamard technique are presented and will be complemented by theoretical explanation of utilizing them for 3D volumetric image generation. Finally measurement results of scene image acquisition are going to be demonstrated and discussed as well as expanded by considerations about possible applications in THz-imaging and the following research steps.

This paper present an unique IR sensor technology capable of providing effective deception and noise jamming IReM capability to ward off threats posed by SFMs or STINGER missiles operated by various terrorist groups and Islamic radicals. More than 60,000 such missiles are currently in the hands of Islamic radicals and terrorist groups. Even one such missile can bring down a commercial jet transport carrying more than 350 passengers. The proposed IReM system deploys innovative jamming technique to confuse the missile seeker receiver by introducing sharp FM-modulated noise spikes in the receiver bandwidth, thereby preventing the detection and tracking of aircraft.

Coded aperture imaging (CAI) has been used extensively at gamma- and X-ray wavelengths, where conventional refractive and reflective techniques are impractical. CAI works by coding optical wavefronts from a scene using a patterned aperture, detecting the resulting intensity distribution, then using inverse digital signal processing to reconstruct an image. This paper will consider application of CAI to the visible and IR bands. Doing so has a number of potential advantages over existing imaging approaches at these longer wavelengths, including low mass, low volume, zero aberrations and distortions and graceful failure modes. Adaptive coded aperture (ACAI), facilitated by the use of a reconfigurable mask in a CAI configuration, adds further merits, an example being the ability to implement agile imaging modes with no macroscopic moving parts. However, diffraction effects must be considered and photon flux reductions can have adverse consequences on the image quality achievable. An analysis of these benefits and limitations is described, along with a description of a novel micro optical electro mechanical (MOEMS) microshutter technology for use in thermal band infrared ACAI systems. Preliminary experimental results are also presented.

Wavefront coding (WFC) is a powerful hybrid optical-numerical technique for increasing the depth of focus of imaging systems. It is based on two components: (1) an optical phase element that codifies the wavefront, and (2) a numerical deconvolution algorithm that reconstructs the image. Traditionally, some sophisticated optical WFC designs have been used to obtain approximate focus-invariant point spread functions (PSFs). Instead, we present a simple and low cost solution, implemented on infrared (IR) cameras, which uses a decentred lens inducing coma as an adjustable and removable phase element. We have used an advanced deconvolution algorithm for the image reconstruction, which is very robust against high noise levels. These features allow its application to low cost imaging systems. We show encouraging preliminary results based on realistic simulations using optical PSFs and noise power spectral density (PSD) laboratory models of two IR imaging systems. Without induced optical phase, the reconstruction algorithm improves the image quality in all cases, but it performs poorly when there are both in and out-of-focus objects in the scene. When using our coding/decoding scheme with low-noise detectors, the proposed solution provides high quality and robust recovery even for severe defocus. As sensor noise increases, the image suffers a graceful degradation, its quality being still acceptable even when using highly noisy sensors, such as microbolometers. We have experienced that the amount of induced coma is a key design parameter: while it only slightly affects the in-focus image quality, it is determinant for the final depth of focus.

We present a passive, solid-state threshold-triggered Wideband Protection Filter (WPF) that blocks the transmission only if the power exceeds a certain threshold. We demonstrate the protection ability of the WPF against laser threats including protection behavior for single and series of pulses. The WPF can be readily used for protection of detectors, cameras, or eye safety.

Active night vision systems based on laser diodes emitters have now reached a technology level allowing military applications. In order to predict the performance of observers using such systems, we built an analytic model including sensor, atmosphere, visualization and eye effects. The perception task has been modelled using the Targeting Task Performance metric (TTP metric) developed by R. Vollmerhausen from the Night Vision and Electronic Sensors Directorate (NVESD). Sensor and atmosphere models have been validated separately. In order to validate the whole model, two identification tests have been set up. The first set submitted to trained observers was made of hybrid images. The target to background contrast, the blur and the noise were added to armoured vehicles signatures in accordance to sensor and atmosphere models. The second set of images was made with the same targets, sensed by a real active sensor during field trials. Images were recorded, showing different vehicles, at different ranges and orientations, under different illumination and acquisition configurations. Indeed, this set of real images was built with three different types of gating: wide illumination, illumination of the background and illumination of the target. Analysis of the perception experiments results showed a good concordance between the two sets of images. The calculation of an identification criterion, related to this set of vehicles in the near infrared, gave the same results in both cases. The impact of gating on observer's performance was also evaluated.

Night-vision systems in vehicles are a new emerging technology. A crucial problem in active (illumination-based) systems is distortion of images by saturation and blooming, due to strong retro-reflections from road signs. In this work we quantified this phenomenon. We measured the Mueller matrices and the polarization state of the reflected light from three different types of road signs commonly used. Measurements of the reflected intensity were taken also with respect to the angle of reflection. We found that different types of signs have different reflection properties. It is concluded from our measurements that the optimal solution for attenuating the retro-reflected intensity is using a linear horizontal polarized light source and a linear vertical polarizer. Unfortunately, while the performance of this solution is good for two types of road signs, it is less efficient for the third sign type.

Test and evaluation of missile warning systems is most efficiently performed using electro-optic stimulation systems that can simulate the launch and approach of a missile at operational ranges. Much research and development over recent years has gone into optimizing the fidelity and power of these systems in the mid-infrared waveband. The work has provided a variety of solutions based generally on black body technology. Recent demands for higher power equipment have pushed development towards a laser based approach. Viable options for laser based architectures have been studied and compared against key criteria such as power input/output, modulation performance, dynamic range, environmental requirements and engineering complexity. An array of quantum cascade lasers has emerged as the most advantageous solution for the present challenges. State of the art quantum cascade lasers from a research institute have been incorporated into the design of two fielded systems. These systems have been thoroughly characterised with results matching the required performance.

Combat Identification is the process of qualifying unidentified objects on the battlefield. This is achieved using a combination of situational awareness and target identification capabilities and is used in conjunction with doctrine, tactics, techniques and procedures to derive an informed decision to shoot or not to shoot. Current electro-optic Cooperative Target Identification (CTI) techniques use a range of sensors operating in the human visible, near infrared and thermal infrared. These sensors are used in conjunction with corresponding markings to comprise what is referred to as the Joint Combat Identification Marking System (JCIMS). There are a number of combat scenarios where CTI could be used for ground-to-ground identification as well as for air-to-ground identification and not all of these scenarios are currently catered for in all sensor wavebands. In this paper we compare some of the existing technologies as well as introducing some new candidates including lightweight flexible thermal infrared marking materials for dismounted troops. An assessment of passive, cooperative CID marking systems such as these is particularly relevant in light of the recent Committee of Public Accounts (CPA) report criticising the delays to proposed active technologies such as the Battlefield Target Identification System (BTIS).

Influence of Kolmogorov and non-Kolmogorov turbulence statistics on imaging system performance in terms of modulation transfer function (MTF) is analyzed for different propagation scenarios.

There are orders of magnitude differences between the ~0.1 % (k=2) uncertainty of NIST reference detector calibrations and the uncertainty of night vision (NV) goggle measurements. NIST developed a night vision radiometer calibration facility including NV radiometer transfer standards. The transfer standards, that propagate the radiance responsivity scale to the military primary standards laboratories, are calibrated against a NIST reference radiometer. The reference radiometer has been calibrated on the NIST Spectral Comparator Facility (SCF) for spectral power and irradiance responsivities. Spectral considerations are discussed to lower the uncertainties of the radiance responsivity scale transfer to the test sets and then to the goggles. Since direct determination of the final uncertainties in goggle calibrations and measurements is difficult, models have been made to estimate the most important uncertainty components based on individual spectral measurements of the applied source distributions and radiometer spectral responsivities. It is also shown, that because of source spectral mismatch problems, the goggle measurement uncertainty at applications can be much higher than at calibration. A suggestion is being made to mimic the no-moon (stars only) night sky radiation distribution using several LEDs in the test-sets to decrease the large spectral mismatch errors. A broad-band correction factor has been developed to further decrease calibration uncertainty when the goggles to be used have different spectral responsivities than the standard. Geometrical considerations to optimize the radiance measurement angle and the out-of-target blocking are also discussed to decrease the uncertainty in the radiance responsivity transfer.

The human visual perception performance results of a dual band near (intensified) and long wave (thermal imager) sniper scope are modeled. This system combines an uncooled focal plane array based thermal imager with an intensifier tube to provide a dual band image. The resulting fused image can obtain any percentage combination of thermal or intensified imagery. A multi-spectral common aperture is utilized to provide parallax free registered images in each spectrum necessary for the sniper scope application. A custom designed eyepiece with a micro display overlays the thermal channel image onto the intensified image. The intensified image is viewed directly on the fiber optic output of the intensifier allowing up to 64lp/mm intensified resolution, equivalent to 2300 resolvable lines maintained in the intensified channel when moonlight is available. A system of this type combines the very high line resolution available from intensifiers with very high spot detection for targets of military interest. The results of an analysis of human visual performance using NVThermIP and IINVD are presented for this dual band common aperture sniper scope.

Automatic acquisition of moving objects from long-distance video sequence is a fundamental task in many applications such as surveillance and reconnaissance. However, the atmospheric degradations, which include blur and spatiotemporal-varying distortions, may reduce the quality of such videos, and therefore, the ability to acquire moving targets automatically. Pervious studies in the field of automatic acquisition of moving objects ignored the blur in the video frames. They usually employed simple methods for noise reduction (such as temporal and spatial smoothing) and motion compensation (registration of frames). The purpose of this work is to determine the effect of image restoration (de-blurring) on the ability to acquire moving objects (such as humans and vehicles) automatically. This is done here by first, restoring the long-distance thermal videos using a novel blind image deconvolution method developed recently, and then comparing the automatic acquisition capabilities in the restored videos versus the non-restored versions. Results show that image restoration can significantly improve the automatic acquisition capability. These results correspond to a previous study which demonstrated that image restoration can significantly improve the ability of human observers to acquire moving objects from a long-range thermal video.

The visualization of IR images on traditional display devices is often complicated by their high dynamic range. Classical dynamic range compression techniques based on simple linear mapping, reduce the perceptibility of small objects and often prevent the human observer from understanding some of the important details. Thus, more sophisticated techniques are required to adapt the recorded signal to the monitor maintaining, and possibly improving, object visibility and image contrast. The problem has already been studied with regard to images acquired in the visible spectral domain, but it has been scarcely investigated in the IR domain. In this work, we address this latter subject and propose a new method for IR dynamic range compression which stems from the lesson learnt from existing techniques. First, we review the techniques proposed in the literature for contrast enhancement and dynamic range compression of images acquired in the visible domain. Then, we present the new algorithm which accounts for the specific characteristics of IR images. The performance of the proposed method are studied on experimental IR data and compared with those yielded by two well established algorithms.

In this paper we study passive focusing techniques for infrared sensors. We present a survey of existing focus measures, i.e. functionals that give an estimate of the quality of focus as a function of the lens position. We synthesize the material proposed in the literature and show that all the approaches exploit the same general layout differing only for the choice of the filtering technique used to extract the image details. We present and discuss experimental results obtained on real infrared data taken in many operating conditions. The experimental analysis aims at comparing the quality of the focus measures and at evaluating their impact of the subsequent algorithm that searches the best focus position of the lens. For this purpose, we propose a comparative analysis based on three important properties of the focus measure: symmetry, smoothness and peakdness.

In this paper, A segmentation model that combines techniques of curve evolution, the Mumford-Shah model and level set method was presented, to detect the contour of object in a given image, the model can detect object whose boundary is not necessarily defined by gradient and whose gray structure may be complicated. First we construct signed distance function, adopted a method which based on the times that is odd or even numbers through close curve from the point along a direction (if need, may be along several directions) to construct sign table. Then we used improved Mumford-Shah model to segment image, we consider that the object to be segmented is made up of some different gray level, it is difficult to detect the object contour using the Mumford-Shah model, for general objects, the contour of the object is piecewise-contour of along the edge, and the gray difference among the object points nearby the contour is little, so we divide the curve into finite segment, compute gray average of narrow band in and out of the curve, and compute the gray difference between the inner narrow band and outer narrow band of the curve, using improved Mumford-Shah model to segment the object. Experiment results show that the proposed algorithm can be used to segment object without edge and with complex gray structure, and the performance of the algorithm is satisfactory.

Tracking deformable objects is very important in many applications such as surveillance, security and military. In this paper, we implement one tracking scheme based on the block matching using PowerPC. We implement tracking algorithm using information from Infrared (IR) sensor for object tracking. When an occlusion occurs, the proposed algorithm predicts movements of an object using the historical tracking information and it can keep the object tracking. Based on experimental results, the proposed system can reduce calculation time and track object under condition of camera jitter and the occlusions.

This paper describes the classification function of naval targets performed by an infrared camera (IR) and an electro-optical camera (EO) that operate in a more complex multisensor system for the surveillance of a coastal region. The following naval targets are considered: high speed dinghy, motor boat, fishing boat, oil tanker. Target classification is automatically performed by exploiting the knowledge of the sensor confusion matrix (CM). The CM is analytically computed as a function of the sensor noise features, the sensor resolution, and the dimension of the involved image database. For both the sensors, a database of images is generated exploiting a three-dimensional (3D) Computer Aided Design (CAD) of the target, for the four types of ship mentioned above. For the EO camera, the image generation is simply obtained by the projection of the 3D CAD on the camera focal plane. For the IR images simulation, firstly the surface temperatures are computed using an Open-source Software for Modelling and Simulation of Infrared Signatures (OSMOSIS) that efficiently integrates the dependence of the emissivity upon the surface temperature, the wavelength, and the elevation angle. The software is applicable to realistic ship geometries. Secondly, these temperatures and the environment features are used to predict realistic IR images. The local decisions on the class are made using the elements of the confusion matrix of each sensor and they are fused according to a maximum likelihood (ML) rule. The global performance of the classification process is measured in terms of the global confusion matrix of the integrated system. This analytical approach can effectively reduce the computational load of a Monte Carlo simulation, when the sensors described here are introduced in a more complex multisensor system for the maritime surveillance.

In this paper we report preliminary data of BIRD640, which is a high-sensitivity (50 mK @ F/1, 60Hz) VGA format detector with 25 μm pitch. This high performance is achieved by utilizing an improved pixel design. The product is architecturally compatible to BIRD384 and contains SCD's proprietary unique features (e.g. "Power-Save", Ambient drift compensation, etc.). The ROIC architecture follows the framework of the previous designs. It consists of an internal timing machine with a single clock that facilitates the system interface. Extensive effort was invested in reducing the detector and system power dissipation. The ROIC supports special "low power" modes, where considerable power is saved with only minor performance degradation. With its superior temporal sensitivity, long-term stability and operational flexibility BIRD640 serves as an ideal candidate for high end and high resolution uncooled VGA systems, particularly hand-held applications.

Single photon detection has a wide variety of scientific and industrial applications including optical time domain reflectometry, astronomy, spectroscopy, defect monitoring of Complementary Metal Oxide Semiconductor (CMOS) circuits, fluorescence lifetime measurement and imaging. In imaging applications, the dead time is the time during which the detector is inhibited after a photon has been detected. This is a limiting factor on the dynamic range of the pixel. The rate of photon detection will saturate if the dead time is too large. Time constants generated by Metal Oxide Semiconductor (MOS) transistor bulk and sidewall capacitances adversely affect the dead time of pixels developed in conventional CMOS technology. In this paper, a novel imaging pixel configuration based on a Geiger Mode Avalanche Photodiode (GMAP) and fabricated using a dedicated hybrid bulk Silicon On Insulator (SOI) CMOS process is presented. The GMAP is fabricated in the bulk layer and the CMOS circuitry is implemented in the upper SOI layers. As a result, bulk and sidewall capacitance effects are significantly reduced. As both the diode and the CMOS transistors are on the same wafer there is a reduction in pixel area and an additional reduction in the parasitic capacitance effects. This leads to a significant improvement in pixel performance. Pixels incorporating 5 micron and 10 micron diameter GMAPs have been simulated. The circuits were optimised with a view to maximising the photon count rate. Results show a significant improvement in the dead time with values of 14 nanoseconds and 15 nanoseconds being observed for the 5 micron and 10 micron GMAPs respectively.

Short wave infrared (SWIR) imaging systems have several advantages due to the spectral content of the nightglow and better discrimination against camouflage. Achieving single photon detection sensitivity can significantly improve the image quality of these systems. However, the internal noise of the detector and readout circuits are significant barriers to achieve this goal. One can prove that the noise limitations of the readout can be alleviated, if the detector exhibits sufficiently high internal gain. Unfortunately, the existing detectors with internal gain have a very high noise as well. Here we present the recent results from our novel FOcalized Carrier aUgmented Sensor (FOCUS). It utilizes very high charge compression into a nano-injector, and subsequent carrier injection to achieve high quantum efficiency and high sensitivity at short infrared at room temperature. We obtain internal gain values exceeding several thousand at bias values of less than 1 volt. The current responsivity at 1.55 μm is more than 1500 A/W, and the noise equivalent power (NEP) is less that 0.5 x10^-15 W/Hz^1/2 at room temperature. These are significantly better than the performance of the existing room temperature devices with internal gain. Also, unlike avalanche-based photodiodes, the measured excess noise factor for our device is near unity, even at very high gain values. The stable gain of the device combined with the low operating voltage are unique advantages of this technology for high-performance SWIR imaging arrays.

This paper reviews specifications and performances of a 160 x 120 uncooled infrared focal plane array made from amorphous silicon micro bolometer with a pixel-pitch of 25 μm, integrated in a LCC package. This detector has been specifically designed for being produced in large volume. The detector has kept all the innovations developed on the full TV format ROIC (detector configuration by serial link, low power consumption or wide electrical dynamic range... ) and offers an advanced TEC-less focal plane array well adapted to low end thermal imaging cameras. The specific appeal of this unit lies in the miniaturization of the packaging and its extremely light weight.In the last part of the paper, we will look more closely at electro-optical performances of this TEC-less product 160 x 120 as well as the other 25 μm products like the 384 x 288. We will insist on the wide thermal dynamic range and the low consumption achieved thanks to the mastering of the amorphous silicon technology coupled with the innovation in the ROIC design.

Several designs that could produce significant wavelength selectivity in micromachined microbolometers are reviewed. These frequency selective surfaces can be achieved using stacks of dielectric coated resistive sheets or by replacing the normal uniform absorbing sheet used in IR microbolometers with true microbolometers (i.e., bolometers that are much smaller than the wavelength) combined with an antenna. Here we discuss dielectric coated designs that can substantially improve the wavelength selectivity of microbolometers.

By forming a Schottky barrier with the contact metal, a semiconducting CNT based Schottky photodiode is formed at the CNT-metal contact. The photogenerated electron-hole pairs within the depletion region of the Schottky barrier are separated by an external electrical field or the built-in field, producing a photocurrent. How to efficiently read this photocurrent signal out is an essential problem for the photodetectors. Since a semiconducting CNT normally forms a Schottky barrier at each CNT-electrode contact, two Schottky photodiodes are reversely connected and their photocurrents will cancel each other, which makes it difficult to measure the overall photocurrent. With different materials as the contact electrodes, the asymmetric structure enlarged the difference between the two CNT-metal contacts. Hence the measurable photocurrent is also enlarged. Furthermore, since the CNT Schottky barrier is determined by the metal work function and the Fermi level of the CNT, the Schottky barrier is able to be adjusted by controlling the Fermi level of the CNT with a gate electrode. In this way, the photocurrent can be optimized to a maximum value by varying the gate voltage. CNT based infrared detectors with different structures were fabricated and tested. Experimental results showed that the asymmetric structure and the gate controlled CNT based photodiode could significantly improve the performance of CNT based infrared detectors.

This paper presents an on-chip 13 bits 10 M/S Analog to Digital Converter (ADC) specifically designed for infrared bolometric image sensor. Bolometric infrared sensors are MEMs based thermal sensors, which covers a large spectrum of infrared applications, ranging from night vision to predictive industrial maintenance and medical imaging. With the current move towards submicron technologies, the demand for more integrated, smarter sensors and microsystems has dramatically increased. This trend has strengthened the need of on-chip ADC as the interface between the analog core and the digital processing electronic. However designing an on-chip ADC dedicated to focal plane array raises many questions about its architecture and its performance requirements. To take into account those specific needs, a high level model has been developed prior to the actual design. In this paper, we present the trade-offs of ADC design linked to infrared key performance parameters and bolometric technology detection method. The original development scheme, based on system level modeling, is also discussed. Finally we present the actual design and the measured performances.

HgCdTe (Mercury Cadmium Telluride / MCT) staring arrays for infrared detection do show constant improvements regarding their compactness and performances. New detectors are now proposed offering system solutions in the different IR wavebands and profiting of the latest technology improvements as well as MCT performance advantages and cost reduction. Among these new detectors, one can find the family of 15 µm pixel pitch detectors including a mid-TV format (384 x 288), a TV format (640 x 512) and a twice-TV format (1280 x 1024). The latest development concerning the mid-TV format is performed according to very challenging specifications regarding small cost and low power consumption. These Focal Plane Arrays (FPA) are integrated in dedicated tactical Dewars, taking advantages on last development in coolers manufacturing and Dewar assembly. Another development axis at CEA\LETI-LIR and Sofradir concerns the avalanche photodiodes for FPA sensitivity improvement. This very promising technology is dedicated for low flux applications as active imagery, hyperspectral applications or small aperture systems. New development results are presented and future trends are discussed.

Realization of affordable large format high performance photovoltaic (PV) infrared (IR) Hg_1-xCd_xTe based focal plane arrays (FPA) covering spectral ranges Mid-Wave (MWIR) from 3 to 5.5 μm and extended Long-Wave (LWIR) from 8 to 14 μm requires comprehensive estimation of photodiodes performance depending on Hg_1-xCd_xTe material properties and operating conditions. Advanced Infrared Focal Plane Arrays include Mid-Wave (MWIR) 3-5.5 μm operating at temperatures T_op=80-100 K and at higher temperatures (HOT) T_op=200-240 K, extended Long-Wave (LWIR) 8-14 μm operating at temperatures T_op=80-100 K and multi-color arrays. Perhaps novel FPA will be based on photodiodes (PD) with p-n junction opposite to usually used n⁺-p junction. PD with optimal p-n junction could have lower dark current value than same size n⁺-p junction. It is desirable for proper multiplexing of PD arrays to Silicon Read-out Integrated Circuits (ROICs). Comparative analysis of LWIR PD performance at 80 K and 100 K is needed also due to strong tendency to lowering weight and power consumption of perspective megapixel FPA. Objective of the present work was to calculate Hg_1-xCd_xTe MWIR and LWIR PV FPA (λp equals to 4.5-4.8 μm at T_op=225 K responding 2-3 stages thermal electric cooler temperature and 8.0-9.0 and 10.0-10.5 μm at T_op=80-100 K) performance variation with doping level, absorber thickness, surface recombination rate and operating temperature.

We propose the infrared (IR) device based on polycrystalline silicon layers what differ in sizes of crystals. Such crystals incorporate into different spatial structures: multilayer structure with several layers of silicon crystals and conglomerates of large microcrystals surrounded by very small nanocrystalline layer. The differentiation in spatial structure results in different electrical signal propagation and photon detection. It can be applicable for sensor and microscale spectroscopic devices design. Hierarchical structures of grown thin silicon film with small and large nanocrystals we can create new photon detector with redistribution of electrical signal according to applied potentials to various silicon layers. The ratio surface/volume for small nanocrystals is high, but the surface area is small, but for large crystals is opposite situation: the small value of ratio surface/volume and large area of surface. Because, there are many small silicon nanocrystalls are bonded with one large silicon crystal. One such node of polycrystalline silicon film can be used for nanoscale device making. Such kind of device is combined as photon detection by nanocrystals and electrical signal distribution by single structural node according to the famous logical rules.

SHG spectra from silicon films with different average size of nanocrystals was studied as possible material for active channel in nonlinear optical switches. It is seen the spectral peak with energy 3.26 eV is related to defects appeared in interface area silicon-silicon dioxide. For films with small silicon crystals (less than 20 nm) the nonlinear optical response contains two spectral peaks. The second peak is caused by optical response from nanocrystal grain boundary that contain oxygen atoms incorporated in silicon as dipoles inside film. The optical nonlinear switch device based on the nonlinear optical response of SiO_x media inside film was proposed. Also, the silicon film with quartz micro-clusters were investigated as material for making the nonlinear optical transmitter device. The PL spectra of films were, also, studied to observe the various silicon and silicon dioxide fractions. The efficiency of transmission of radiation is sufficient.

Bad pixels are spatial or temporal noise which arise from dead pixels by fixed signal levels or blinking pixels by variable signal levels that go beyond the bounds of normal pixel levels at the temperature. Because bad pixels are the false targets over infrared imaging system for tracking, those must be corrected. Main contribution to the number of bad pixels is fixed pattern noise (FPN) according to increasing array size. And it is more simple to establish whether FPN is or not through analyzing of accumulated frames. But it needs to calculate with more complex implementation such standard deviation from frame to frame in case of the temporal noise. Both cases it is very important to establish the threshold levels for identifying at variable operating temperatures. In this paper, we propose a more efficient data analysis method and a temporal noise identification method using adaptive threshold for infrared imaging system, and the hardware is implemented to identify and replace bad pixels. And its result is confirmed visually by bad pixel map images.