This PDF file contains the front matter associated with SPIE Proceedings Volume 6542, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and the Conference Committee listing.

We report progress in the development of long wavelength infrared (LWIR) focal plane arrays (FPAs) built on type-II strained layer InAs/GaSb superlattice materials. Work at Raytheon Vision Systems and Jet Propulsion Laboratory has led to successful devices with cutoff wavelengths in the 10 to 12 μm range. Pixels have been formed by wet etching and surface passivation by plasma-deposited silicon dioxide. We present test results on arrays hybridized with indium bump bonding to silicon readout integrated circuits, as well as analyses of current-voltage characteristics of individual diodes. In particular, we find that, at temperatures below about 70 K the leakage current is dominated by generation-recombination effects near zero bias and by trap-assisted tunneling in reverse bias. Although other authors have demonstrated imaging for SWIR and MWIR type-II superlattice devices, to our knowledge no one has done so prior to 2006 in the LWIR range. We have obtained both still and video imaging with 256×256 arrays with 30-μm pixels operating at 78 K, having high operability and a cutoff wavelength of 10.5 μm.

A critical step in developing type-II superlattice (T2SL) based LWIR focal plane array (FPA) technology is to achieve high performance levels in FPA pixel-sized devices having 20-40 μm pitch. At this scale, device performance tends to be limited by surface effects along mesa sidewalls which are etched to provide pixel isolation. While control of surface leakage has been achieved for MWIR T2SLs, as evidenced by the availability of commercially produced FPAs, the same cannot be said for LWIR T2SLs. Several groups have approached this problem as strictly a matter of surface treatment, including cleaning, chemical treatment, and dielectric coating or epitaxial overgrowth, but with limited success. Here we describe an approach based on shallow-etch mesa isolation (SEMI), which takes advantage of bandgap grading to isolate devices without exposing narrow-gap LWIR regions on diode mesas sidewalls. The SEMI process consists of defining mesa diodes with a shallow etch that passes only 20-100 nm past the junction of a graded-gap "W"-structured type-II superlattice p-i-n structure, where the bandgap remains large (>200 meV). A second, deeper etch is then used to define a trench along the chip border for access to the p-contact. As a result, SEMI diodes have only MWIR layers exposed along sidewalls, while the LWIR regions remain buried and unexposed. We also discuss an investigation of surface passivation of GaSb with sulfur using thioacetamide.

In the past few years, significant progress has been made in the structure design, growth and processing of Type-II InAs/GaSb superlattice photodetectors. Type-II superlattice demonstrated its ability to perform imaging in the middle and long infra-red range, becoming a potential competitor for technologies such as QWIP and HgCdTe. Using an empirical tight-binding model, we developed a superlattice design that matches the lattice parameter of GaSb substrates and presents a cutoff wavelength of 12 &mgr;m. Electrical and optical measurements performed on single element detectors at 77 K showed an R0A averaging 13 &OHgr;.cm² and a quantum efficiency as high as 54%. We demonstrated high quality material growth with x-ray FWHM below 30 arcsec and an AFM rms roughness of 1.5 Å over an area of 20x20 &mgr;m². A 320x256 array of 25x25&mgr;m² pixels, hybridized to an Indigo Read Out Integrated Circuit, performed thermal imaging up to 185 K with an operability close to 97%. The noise equivalent temperature difference at 81 K presented a peak at 270 mK, corresponding to a mean value of 340 mK.

We report on the status of GaSb/InAs type-II superlattice diodes grown by molecular beam epitaxy (MBE) and designed for infrared absorption in the 2-5μm and 8-12&mgr;m bands. Recent LWIR devices have produced detectivities as high as 8x10¹⁰ Jones with a differential resistance-area product greater than 6 Ohmcm² at 80K with a long wavelength cutoff of approximately 12&mgr;m. The measured quantum efficiency of these front-side illuminated devices is close to 30% in the 10-11μm range. MWIR devices have produced detectivities as high as 8x10¹³ Jones with a differential resistance-area product greater than 3x10⁷ Ohmcm² at 80K with a long wavelength cutoff of approximately 3.7μm. The measured quantum efficiency of these front-side illuminated MWIR devices is close to 40% in the 2-3μm range at low temperature and increases to over 60% near room temperature. Initial results on SiO₂ and epitaxial-regrowth based passivation techniques are also presented.

The fabrication and optimization of InAs/GaSb type-II superlattice (SL) detectors for single-color and dual-color focal plane arrays in the mid-wavelength infrared spectral range between 3-5 &mgr;m is reported. Single color focal plane arrays with 288 x 384 detector elements and 24 &mgr;m pitch have been fabricated with high pixel yield. Camera systems with InAs/GaSb SL detectors reveal NETD values of 27.9 mK at a cut-off wavelength of &lgr;_c = 4.9 &mgr;m for an integration time of only 1 msec with F#/2.4 optics. A dual-color MWIR/MWIR InAs/GaSb SL camera, developed for missile approach warning systems, features simultaneous and spatially coincident detection for both spectral channels on each pixel. The camera system with 288 x 384 detector elements in 40 &mgr;m pitch shows excellent NETD values and high pixel operability. The fabrication of dual-color focal plane arrays on 3" GaSb substrates is presented.

The 3rd generation of infrared (IR) detection modules is expected to provide advanced features like higher resolution 1024x1024 or 1280x720 pixels and/or new functions like multicolor or multi band capability, higher frame rates and better thermal resolution. This paper is intended to present the current status and trends at AIM on antimonide type II superlattices (SL) dual color detection module developments for ground and airborne applications in the high performance range, where rapidly changing scenes - like e.g. in case of missile warning applications for airborne platforms or ground based sniper detection systems - require temporal signal coincidence with integration times of typically 1ms. AIM and IAF selected antimonide based type II superlattices (SL) for such kind of applications. The type II SL technology provides - similar to QWIP's - an accurate engineering of sensitive layers by MBE with very good homogeneity and yield. IAF and AIM managed already to realize a dual color 384x288 IR module based on this technology. It combines spectral selective detection in the 3 - 4&mgr;m wavelength range and 4 - 5 &mgr;m wavelength range in each pixel with coincident integration in a 384x288x2 format and 40x40 &mgr;m² pitch. Excellent thermal resolution with NETD < 12 mK @ F/2, 2.8 ms for the longer wavelength range (red band) and NETD < 22 mK @ F/2, 2.8 ms for the shorter wavelength range (blue band) were reported. In the meantime a square design of 256x256x2 pixel with a reduced pitch of 30x30 &mgr;m² is in preparation. In this case with 2 Indium bumps per pixel and a third common contact for all pixels required for temporal coincidence is connected at the outer area of the array. The fill factor is approx. 65% for both wavelength ranges. The reduced size of the array enables the use of a smaller dewar with reduced cooling power and significantly reduced weight and broadens the scope of applications where weight and costs is essential. Design aspects and expected performances are discussed.

Type-II InAs/GaSb superlattice photodiodes for mid-IR (3-5μm) region grown by solid-source molecular beam epitaxy are reported. Different approaches for realization of high quality interfaces between compositionally abrupt GaSb and InAs layers during the growth of the SLs are discussed. Mid wave infrared (&lgr;c~ 4.5 µm at T=300K) P-on-N designs of SLs detectors were developed to ensure compatibility with most present day readout integrated circuits (ROICs). Variable size diode arrays were fabricated using standard photolithography technique and hybridized to silicon fanout chip. The sizes of the detector mesas were varied from 29μm x 29μm to 804μm x 804μm. The single pixel characterization was undertaken at Santa Barbara Focal Plane. Temperature-dependent IV measurements revealed dark current density below 1 x 10^-8 A/cm² at 82K and below 2 x 10^-5 A/cm² at 240K. (V_bias = 0V). Dynamic resistance-area product at zero bias was found to be ~ 1 x 10⁵ Ωcm² at 82K and 0.24 Ωcm² at 240K. Influence of protective silicon nitride coating on reduction surface leakage currents of detectors was investigated. We found that r_surface was equal to ~ 3 x 10⁶ Ωcm indicating the proper surface preparation followed by room temperature Si₃N₄ deposition is effective in reduction of leakage currents in type-II MWIR InAs/GaSb superlattice photodiodes.

Type II superlattce photodetectors have recently experienced significant improvements in both theoretical structure design and experimental realization. Empirical Tight Binding Method is initiated and developed for Type II superlattice. Growth characteristics such as group V segregation and incorporation phenomena are taken into account in the model and shown higher precision. A new Type II structure, called M-structure, is introduced and theoretically demonstrated high RoA, high quantum efficiency. Device design is optimized to improve the performance. As a result, 55% quantum efficiency and 10 Ohm.cm² RoA are achieved for an 11.7 &mgr;m cut-off photodetector at 77K. FPA imaging at longwavelength is demonstrated with a capability of imaging up to 171K. At 81K, the noise equivalent temperature difference presented a peak at 0.33K.

This paper reports on the IR system level modeling for a FPA based on type II superlattice photodiodes. The predicted performance of the super lattice detectors is based on published values from device models and measured results. A top level description of the sensor model is given and how it is used to determine system level trades. Results of these trades provide valuable feedback to developers of type II superlattice devices, arrays and readout circuits. Trades between IR FPA technologies can be made to aid the IR system developer to make informed decisions relative to risk and performance early in the program cycle. IR band selection is a complex trade of target signature, background, detector technologies and optical response. This paper explores these considerations for single and multicolor applications.

Performance of HgCdTe detector technology surpasses all others in the mid-wave and long-wave infrared spectrum. This technology is relatively mature with current effort focused on improving uniformity, and demonstrating increased focal plane array (FPA) functionality. Type-II superlattice (InAs-GaSb and related alloys) detector technology has seen rapid progress over the past few years. The merits of the superlattice material system rest on predictions of even higher performance than HgCdTe and of engineering advantages. While no one has demonstrated Type-II superlattice detectors with performance superior to HgCdTe detectors, the difference in performance between these two technologies is decreasing. In this paper, we review the status and highlight relative merits of both HgCdTe and Type-II superlattice based detector technologies.

Research on Mercury Cadmium Telluride (HgCdTe or MCT) and group III-V based infrared materials is being conducted for the development of advanced, especially large area IR detector and focal plane arrays. The focus of this research has been on materials for Quantum Well Infrared Photo Detectors (QWIPs), Sb based type II superlattice detectors, Silicon based substrates for MCT detectors and MCT detectors with higher operating temperature. Recently research has been initiated in dilute Nitride materials. To improve the quantum efficiency, reproducibility and operating temperature of the QWIP detectors, a corrugated design has been implemented. For superlattice detectors, focal plane arrays for the MWIR spectral band have been successfully demonstrated and good image quality has been obtained. Current efforts are concentrated on achieving high quality materials and passivation techniques for the LWIR spectral band. A recently initiated effort on dilute Nitride materials holds the premise to obtain high quality direct bandgap detectors with III-V materials. For MCT detectors on Si based substrates MWIR detectors have been demonstrated with high quality, but for LWIR detector arrays of sufficient low defect densities have not been obtained on a consistent basis. Recent efforts showing promising results will be discussed.

In this paper we present an overview of the very recent developments of the HgCdTe infrared detector technology developed by CEA-LETI and industrialized by Sofradir in France. Today Sofradir uses in production for more than 15years a very mature, reproducible, well mastered and fully understood, planar n on p ion implanted technology. This process that allows very high yields to be achieved in all infrared bands from SWIR to LWIR uses the very conventional approach of LPE growth of MCT on lattice-matched CdZnTe substrates. Progress in this field is continuous from 20years and has recently leaded to the fabrication of high performance VLWIR FPA (320x256 with cut off wavelengths as high as 20μm). Moreover, thanks to the design of the epitaxial structure and to the substrate removal step MCT FPAs present the unique features to have very high quantum efficiency (above 70%) from the cut off wavelength down to the UV. This effect, which opens new application fields, was recently demonstrated in SWIR 320x256 FPAs with cut off wavelength of 2.5μm. Very high quality FPAs (1280x1024) with pitches as small as 15μm have already been demonstrated last year using the MBE growth of MWIR MCT epilayers on 4 inches germanium substrates, n on p ion implanted photodiodes and the hot welding indium bump hybridization technique. At the same time, with the MBE growth, bicolor and dual band FPAs which uses more complex multi hetero-junctions architectures (both 4 layers npn and 'pseudo planar' structures and extrinsically doped MCT layers) were fabricated with formats of 320x256 and pitches as small as 25μm. A very new area of development concerns avalanche photodiodes (APD) made with MCT. This semiconductor presents a unique feature among all the over semiconductors. Extremely high avalanche gains can be obtained on n on p photodiodes without absolutely any noise excess (F(K)=1): MCT APDs act as perfect amplifiers. These results open new interesting fields of investigation for low flux applications and fast detectors (including hyper spectral imaging and active imaging).

In this work gated midwave infrared (MWIR) Hg_1-xCd_xTe photodiodes are used to investigate the physical origin of 1/f noise generation. Gated photodiodes were fabricated on liquid phase epitaxy p-type HgCdTe MWIR material with a vacancy doped concentration of 1.6 x 10¹⁶cm^-3 and x = 0.31. CdTe was thermally deposited and used as both a passivant for the HgCdTe and a mask for the plasma-based type conversion, and ZnS was used as an insulator. Fabricated devices show a R₀A of 1-5x10⁴&OHgr;cm² at 77K with zero gate bias. Application of 2V to the gate improves the R₀A by more than two orders of magnitude to 6.0 x 10⁶&OHgr;cm², which corresponds to the p-type surface being at transition between depletion and weak inversion. Trap-assisted tunelling (TAT) current was observed at negative gate biases and reverse junction biases. For gate biases greater than 3V a field-induced junction breakdown was observed. Gated photodiodes show diffusion limited behaviour at zero bias above 200K, and TAT, band-to-band tunnelling, and generation-recombination (GR) limited behaviour below, for gate biases from -8V to 8V. Field-induced junction breakdown current was also observed to be temperature independent. Noise current, I_n = &agr;I&bgr;f^-0.5 trend was observed above 200pA reverse bias dark current, with &agr; = 3.5 x 10^-5 and &bgr; = 0.82, which corresponds to the TAT dominated region. Below 200pA, junction GR current starts to dominate and this previously mentioned trend for I_n is no longer observed. Junction GR current was not seen to be correlated with 1/f noise in these photodiodes.

In recent years, the interest in infrared imaging systems has broadened from the classical MWIR (3-5 &mgr;m) and LWIR (8-12 &mgr;m) spectral bands to the SWIR (1-3 &mgr;m) and VLWIR (12-15 &mgr;m). The atmospheric transmission windows (MWIR, LWIR) are the preferred spectral region for panchromatic night vision systems to display temperature contrasts. Whereas the characteristic absorption and emission signatures in the SWIR and VLWIR make these bands well suited for remote sensing of material composition (hyperspectral imaging). In the standard bands, AIM has constantly improved homogeneity and reduced the number of defects of its FPAs. We obtain for instance 0.38% defective pixels for 384 x 288 LW arrays. Our FPAs withstand >9'000 thermal cycles without degradation. The improved reliability is based on substrate removal and applying a thermally matched underfiller. For hyperspectral imaging applications, a 1024 x 256 SWIR array with 245 Hz frame rate for low photon fluxes with CTIA input stage was developed. For VLWIR applications we built a 256 x 256 array with 880 Hz frame rate that has a cut-off wavelength of >13 &mgr;m at 40 K. AIM's IR detectors cover the whole spectral range from 0.9 to 13 &mgr;m.

Intrinsic carriers play a dominant role especially in the long wavelength (8-12 μm cut-off) HgCdTe material near ambient temperatures due to high thermal generation of carriers. This results in low minority carrier lifetimes caused by Auger recombination processes. Consequently, this low lifetime at high temperatures results in high dark currents and subsequently high noise. Cooling is one means of reducing this type of detector noise. However, the challenge is to design photon detectors to achieve background limited performance (BLIP) at the highest possible operating temperature; with the greatest desire being close to ambient temperature operation. We have demonstrated a unique planar device architecture using a novel approach in obtaining low arsenic doping concentrations in HgCdTe. Results indicate Auger suppression in P⁺/π/N⁺ devices at 300K and have obtained saturation current densities of the order of 3 milli Amps-cm² on these devices.

This paper reports the development of mid-wave 320x256 HgCdTe IRFPA with 30μm pixel pitch since 2002 in Korea. All key technologies such as HgCdTe photodiode array fabrication process, the design of silicon readout integrated circuit and hybridization process between HgCdTe photodiode array and ROIC including underfill encapsulation process are studied and realized. The fabricated IRFPA shows good electro-optical performances such as operability over 99%, NETD of ~ 17mK and there is no degradation in the operability during 500 thermal cycles.

This paper describes the fabrication and performance of affordable LW infrared focal plane arrays (IRFPAs) made from HgCdTe (MCT) grown by Metal Organic Vapour Phase Epitaxy (MOVPE) bump bonded to silicon read-out integrated circuits (ROICs). The growth substrate is GaAs, being readily available from several sources and suitable for wafer scale processing. Arrays of size up to 640x512 at 24 μm pixel pitch have been produced, encapsulated, and demonstrated in a camera system. Arrays of this size are produced in n-on-p material, that is, the common layer is p-type. This orientation is chosen from a contact technology viewpoint. It is shown that at higher biases trap-assisted tunnelling (TAT) can limit the performance of arrays. This becomes an issue for large arrays at high infrared flux with a p-type common layer due to its inherent higher sheet resistance compared to n-type, this can result in debiassing of the central elements. The key is found to be the control of the MCT structure and quality to ensure good diode performance with minimal TAT, allowing the higher biases needed to overcome debiassing.

Inductively coupled plasma (ICP) chemistry based on a mixture of CH₄, Ar, and H₂ was investigated for the purpose of delineating HgCdTe mesa structures and vias typically used in the fabrication of second and third generation infrared photo detector arrays. We report on ICP etching uniformity results and correlate them with plasma controlling parameters (gas flow rates, total chamber pressure, ICP power and RF power). The etching rate and surface morphology of In-doped MWIR and LWIR HgCdTe showed distinct dependences on the plasma chemistry, total pressure and RF power. Contact stylus profilometry and cross-section scanning electron microscopy (SEM) were used to characterize the anisotropy of the etched profiles obtained after various processes and a standard deviation of 0.06 &mgr;m was obtained for etch depth on 128 x 128 format array vias. The surface morphology and the uniformity of the etched surfaces were studied by plan view SEM. Atomic force microscopy was used to make precise assessments of surface roughness.

The DARPA PCAR program is sponsoring the development of low noise, near infrared (1.5 &mgr;m wavelength) focal plane arrays (FPAs) for night vision applications. The first phase of this work has produced a collection of 640 x 512 pixel, 20 &mgr;m pitch FPAs with low noise. The approach was to design four different read out integrated circuits (ROICs), all compatible with the same bump-bonded InGaAs photodiode detector array. Two of the designs have capacitive transimpedance amplifier (CTIA) pixels, each with a somewhat different amplifier design and with two different sizes of small integration capacitors. The third design is a source follower per detector (SFD) pixel, integrating on the detector capacitance. The fourth design also integrates on the detector capacitance, but uses a moderate gain, in-pixel amplifier to boost the signal level, and also has a differential pixel output. All four designs require off-chip correlated sampling to achieve the desired noise level. The correlated sampling is performed digitally in the data acquisition software. Each design is capable of 30 frames per second read out rate, and has a dynamic range of 1000:1 using a rolling, non-snapshot integration. The designs were fabricated in a standard CMOS foundry process, and were bump-bonded to InGaAs detector arrays. All four designs are working without any significant design errors, and are producing low noise imaging, with less than 50 electrons rms noise per pixel after correlated double sampling.

Under the DARPA Photon Counting Arrays (PCAR) program we have investigated technologies to reduce the overall noise level in InGaAs based imagers for identifying a man at 100m under low-light level imaging conditions. We report the results of our experiments comprising of 15 InGaAs wafers that were utilized to investigate lowering dark current in photodiode arrays. As a result of these experiments, we have achieved an ultra low dark current of 2nA/cm² through technological advances in InGaAs detector design, epitaxial growth, and processing at a temperature of +12.3°C. The InGaAs photodiode array was hybridized to a low noise readout integrated circuit, also developed under this program. The focal plane array (FPA) achieves very high sensitivity in the shortwave infrared bands in addition to the visible response added via substrate removal process post hybridization. Based on our current room-temperature stabilized SWIR camera platform, these imagers enable a full day-night imaging capability and are responsive to currently fielded covert laser designators, illuminators, and rangefinders. In addition, improved haze penetration in the SWIR compared to the visible provides enhanced clarity in the imagery of a scene. In this paper we show the results of our dark current studies as well as FPA characterization of the camera built under this program.

We have developed a microspectrometer based on monolithic integration of a Fabry-Perot optical filter directly with a Hg_xCd_1-xTe-based infrared detector. The tunable Fabry-Perot is created by a parallel plate MEMS fabricated from two dielectric mirror stacks separated by an initial air gap of 1.4 μm. We have measured linewidths as low as 55 nm, switching times of 40 μs and a tuning range of 380 nm. However this tuning corresponds to only 42% of the desired tuning range, from 1.6-2.5 μm (900 nm). The tuning range is limited by a process called "snap down" which occurs when the MEMS is drive by a voltage source. It can be shown that for a parallel plate snap down occurs at 1/3 the initial gap; complete tuning across the SWIR band requires a physical deflection of at least 60% of the gap. We have developed a modified actuator design which allows 60% tuning of the moveable mirror. Further, the method minimizes actuation-induced stress gradients which can lead to substantial bowing of the mirror and subsequently broad optical linewidths. We will compare the results of our current microspectrometer with our new extended tuning designs. These designs are based on Coventorware and analytical mechanical models combined with optical models for the Fabry- Perot.

A unidirectional intracavity pump scheme was demonstrated efficient for tunable quantum information interface capable of transferring quantum bits between photons of different wavelengths. By means of sum frequency generation in a periodically poled lithium niobate crystal placed inside a diode-pumped Nd:GdVO₄ laser cavity, single photons at telecom wavelength were upconverted into replicas around 630 nm with preserved quantum features, which could be easily tuned by adjusting the intracavity pump wavelength.

Short-wave infrared (SW-IR) radiometers have been developed to extend the NIST reference responsivity scales from the silicon wavelength range to 2500 nm. In addition to spectral power responsivity measurements, where 5 mm diameter extended-InGaAs (EIGA) detectors are underfilled by the incident radiation, irradiance responsivity calibrations are needed. Irradiance measuring radiometers are used as reference detectors to calibrate field radiometers in both irradiance and radiance measurement modes. In irradiance mode, smaller detectors with high shunt resistance, such as 1 mm diameter short-wave HgCdTe and EIGA detectors are used. Mechanical, optical, thermal, and electronic design considerations of SW-IR radiometers are discussed. Noise equivalent currents (NEC) were measured to evaluate noise equivalent power (NEP) and D*.

In this work, the 30 stacked InAs/GaAs quantum dot infrared photodetector (QDIP) structure was grown by solid-source molecular beam epitaxy technique and demonstrated with dual-band mid- (2.7~5.6μm) and long- (7.5~13.5μm) wavelength normal-incident detections without grating and passivated process for 256×256 FPA. The 256 ×256 QDIP FPA hybridized with snapshot-mode ROIC was mounted in a 68 pin leadless ceramic chip carrier which was put in the testing dewar with IR optical cold spectral filters of the 2.9~5.5μm and 6.5~14.5 μm for the dual-band IR detections, respectively. The testing scheme for thermal imaging uniformity of the InAs/GaAs QDIP focal plane array (FPA) has been proposed and calibrated using a plane-typed blackbody source of a high temperature of 373±1K and lower ambient temperature for the two-point temperature correction. The averaged of specific detectivity (D*) and operability of the QDIP FPA have reached 1.5×10¹⁰cm-Hz^1/2/W and 99% at 80K, respectively. The dominant noise equivalent temperature differences (NEDT) of typical figure of merit for QDIP thermal imaging module operated under the temperature of 80K, device biases of -0.7 V and integration time of 32ms with infrared optics and two-point temperature correction (T_L =R.T. and T_H= 200 °C) are 1.065 K (mid-wavelength IR) and 131mK (long-wavelength IR), respectively. Meanwhile, it is worth to note that these are the first confirmation for dual-band detections of FPA from direct InAs quantum dots matrix embedded in GaAs heterostructure. In the future, the dual-band IR QDIP FPA will become one of the important candidates for hyper-spectral detection and thermal imaging fusion application.

We present an electrically-controllable multi-spectral quantum dot infrared photodetector (QDIP). The QDIP consists of vertically-stacked InAs quantum dots layers with two different capping layers for MWIR and LWIR absorption, respectively. The multi-spectral QDOP is capable of simultaneously detecting multi-spectral normal incidence through inter-subband transitions in the three-dimensional (3-D) confined quantum dot nanostructures. The QDIP showed multi-color IR detection bands centered at 5.6μm, 7.7 μm and 10.0μm, respectively. By tuning the bias voltage, the detection band can be individual turned on. High photodetectivity of > 2.3×10¹⁰cmHz^1/2/W were obtained for these IR detection bands. The voltage-controllable detection band selection enables real-time system reconfiguration to focus on the band of interest. The vertically-stacked device structure allows easy construction of focal plane arrays (FPA).

Self-assembled semiconductor quantum dots have attracted much attention because of their novel properties and thus possible practical applications including the lasers, detectors and modulators. Especially the photodetectors which have quantum dots in their active region have been developed and show promising performances such as high operation temperature due to three dimensional confinement of the carriers and normal incidence in contrast to the case of quantum well detectors which require special optical coupling schemes. Here we report our recent results for mid-wavelength infrared quantum dot infrared photodetector grown by low-pressure metalorganic chemical vapor deposition. The material system we have investigated consists of 25 period self-assembled InAs quantum dot layers on InA1As barriers, which are lattice-matched to InP substrates, covered with InGaAs quantum well layers and InA1As barriers. This active region was sandwiched by highly doped InP contact layers. The device operates at 4.1 μm with a peak detectivity of 2.8×10¹¹ cmHz^1/2/W at 120 K and a quantum efficiency of 35 %. The photoresponse can be observed even at room temperature resulting in a peak detectivity of 6×10⁷ cmHz^1/2/W. A 320×256 focal plane array has been fabricated in this kind of device. Its performance will also be discussed here.

Recently, large format and high quantum efficiency corrugated quantum well infrared photodetector (C-QWIP) FPAs have been demonstrated. Since the detector light coupling scheme does not alter the intrinsic absorption spectrum of the material, the QWIPs can now be designed with different bandwidths and lineshapes to suit various applications. Meanwhile, the internal optical field distribution of the C-QWIPs is different from that of a grating coupled detector, the material structure thus should be designed and optimized differently with respect to quantum efficiency, conversion efficiency and operating temperature. In this paper, we will provide a framework for the material design. Specifically, we will present a theoretical detector performance model and discuss two specific examples, namely with 9.2 and 10.2 μm cutoff wavelengths. We found that for both λ_c, the photocurrent to dark current ratio is maximized at an electron doping density N_D of 0.28 × 10¹⁸ cm^-3. The dark current limited detectivity meanwhile reaches a maximum at a higher N_D of 0.45 × 10¹⁸ cm^-3. But the lowest noise equivalent noise temperature difference is actually obtained at an even higher N_D of 1.0 × 10¹⁸ cm^-3 due to the larger quantum efficiency, if there are no limitations on the readout charge capacity. These predictions are compared with the data of a 1024 × 1024 C-QWIP FPA hybridized to a fan-out circuit, and the results are consistent.

In the rapid development of GaAs Quantum Well Infrared Photodetectors (QWIPs) we have fabricated a 1,024 x 1,024 (1K x 1K), 8-12 μm infrared focal plane array (FPA). This focal plane array is a hybrid using an L3 Cincinnati Electronics silicon readout integrated circuit (ROIC) bump bonded to the 1 megapixel GaAs QWIP. This effort was a collaboration of engineers at the Goddard Space Flight Center (GSFC), the Army Research Laboratory (ARL) and L3 Cincinnati Electronics (L3). We have integrated this focal plane into an SE-IR based imaging camera system and performed tests over the 55K-77K temperature range. As in previous developments the ease of fabrication of the GaAs array continues to be a valuable asset. The overall focal plane development costs are currently dominated by the costs associated with the silicon readout/hybridization. The GaAs array fabrication is based on a high yield, well-established GaAs processing capability. The broadband long wavelength response of this array combined with markedly improved quantum efficiency is of particular value in science applications where spectroscopy is required. One of the features of GaAs QWIP technology is the ability to precisely design and fabricate arrays responsive to a particular IR spectral region but the spectral response is typically only a few tenths of a micrometer wide limiting the spectral information content. By broadening the spectral response of this device the applications for imaging and spectroscopy are substantially increased. In this paper we will present the latest results of our corrugated 1K x 1K, 8-12 μm infrared focal plane array development including fabrication methodology, test data and experiments.

We report on the first demonstration of a large format (640x512), small pitch (20&mgr;m), polarization sensitive long-wave infrared focal plane array. The choice of quantum well infrared photodetectors allows the monolithic integration of the polarizing element (1D gratings) into the focal plane array. The performance (response, NETD) under natural light is identical to that of polarization insensitive focal plane arrays, with the same pitch. Polarization contrast capabilities are investigated experimentally and are shown to be compatible with polarimetric imaging needs. Responsivity contrasts higher than 35% are obtained, on square 18.6&mgr;m pixels. Preliminary results on extremely compact arrays (15&mgr;m pitch) are presented.

The ongoing development of QWIP focal plane arrays at IRnova (formerly Acreo) has resulted in the launch of several new formats up to 640 by 512 pixels and the introduction of major improvements to all products. The achieved performance and imagery will be evaluated. In the light of the development of new formats, the results of hybridization a 640 by 512 detector with 20 &mgr;m pitch will be discussed. The driving forces behind these improvements have been the demands from both industrial applications where the requirements for the operating temperature are high due to the life time issues, and from space applications where the requirements for the quantum efficiency and dark current are extreme. For the latter type of applications a number of QWIPs covering the 4 to 20 &mgr;m wavelength band have been grown and evaluated. The demands for better performance are met by ongoing increases in light coupling, improvements of the quantum well structures, as well as fine tuning of the epitaxial growth parameters. This has led to FPAs that can operate at 75 K and operation close to 80 K is within reach. IRnova is also looking at other material systems to fulfill the requirements of next generation photon detectors.

Mid-wavelength infrared (MWIR) and long-wavelength infrared (LWIR) 1024x1024 pixel InGaAs/GaAs/AlGaAs based quantum well infrared photodetector (QWIP) focal planes have been demonstrated with excellent imaging performance. The MWIR QWIP detector array has demonstrated a noise equivalent differential temperature (NE&Dgr;T) of 17 mK at a 95K operating temperature with f/2.5 optics at 300K background and the LWIR detector array has demonstrated a NE&Dgr;T of 13 mK at a 70K operating temperature with the same optical and background conditions as the MWIR detector array after the subtraction of system noise. Both MWIR and LWIR focal planes have shown background limited performance (BLIP) at 90K and 70K operating temperatures respectively, with similar optical and background conditions. It is well known that III-V compound semiconductor materials such as GaAs, InP, etc. are easy to grow and process into devices. In addition, III-V compound semiconductors are available in large diameter wafers, up to 8-inches. Thus, III-V compound semiconductor based infrared focal plane technologies such as QWIP, InSb, and strain layer superlattices (SLS) are potential candidates for the development of large format focal planes such as 4096x4096 pixels and larger. In this paper, we will discuss the possibility of extending the infrared detector array size up to 16 megapixels.

Since 2002, the THALES Group has been manufacturing sensitive arrays using QWIP technology based on GaAs and related III-V compounds, at THALES Research and Technology Laboratory. The QWIP technology allows the realization of large staring arrays for Thermal Imagers (TI) working in the long-wave infrared (LWIR) band (8-12 μm). In the past researchers claimed many advantages of QWIPs. Uniformity was one of these and has been the key parameter for the production to start. The 640x512 LWIR focal plane arrays (FPAs) with 20μm pitch was the demonstration that state of the art performances can be achieved even with small pixels. This opened the field for the realization of usable and affordable megapixel FPAs. Thales Research & Technology (TRT) has been developing third generation GaAs LWIR QWIP arrays for volume manufacture of high performance low cost thermal imaging cameras. In the past, another widely claimed advantage for QWIPs was the so-called band-gap engineering and versatility of the III-V processing allowing the custom design of quantum structures to fulfil the requirements of specific applications such as very long wavelength (VLWIR) or multispectral detection. In this presentation, we present the performances of both our first 384x288, 25 μm pitch, MWIR (3-5μm) / LWIR (8-9 μm) dual-band FPAs, and the current status of QWIPs for MWIR (< 5μm) and VLWIR (>15μm) arrays.

Cameras operating in the thermal infrared (mid-wave and long-wave IR) use a cold stop that is designed to match the exit pupil of the optics and thus avoid parasitic radiation or vignetting. For years, range operators have been using reflective telescopes, usually with photo-documentation film cameras. Along with the need to shift operation into the infrared comes a problem that (i) these telescopes do not have an exit pupil located at the IR camera cold stop, and (ii) most IR cameras have f/2 or f/4 stop, while the telescope is typically f/7 or greater. These mismatches cause a significant deterioration of the system performance and picture quality. A similar need arises when using zoom optics with IR cameras where, as the field of view changes, so does the optics f/#, creating a mismatch with the camera that has a fixed aperture. The OKSI/WSMR team has demonstrated two implementations of a patented continuous variable aperture / cold stop (CVA/CS or VariAp®) for operating IR cameras with different f/# optics. Two systems were built: (1) an optical relay assembly with an external CVA/CS, and (2) a custom 1024×1024 pixel MWIR camera with a built in CVA/CS and the proper relay optics to match the telescope optics to the camera. The first optical relay with the VariAp® is a retrofit for legacy IR cameras for operations with reflective telescopes. The camera with the built-in VariAp® can function with both reflective (using an additional external relay) and refractive (with no additional relay) telescopes. The paper describes the two systems that open new possibilities in IR imaging for various ranges.

Negative luminescent (NL) devices, which to an IR observer can appear colder than they actually are, have a wide range of possible applications, including use as modulated IR sources in gas sensing systems and as thermal radiation shields in IR cameras. A further important use would be a calibration source for IR focal plane arrays where there are many potential advantages over conventional sources, including high speed operation (for multi-point correction) and lower power consumption. Such applications present considerable technological challenges as they require large area uniform devices (>1cm²) with a large apparent temperature range. In this paper we report on recent progress in fabricating large area (1.5cm × 1.5cm) negative luminescence devices from Hg_1-xCd_xTe grown on silicon substrates using a segmented device architecture.

The drive towards improved target recognition has led to an increasing interest in detection in more than one infrared band. This paper describes the design, fabrication and performance of two-colour and three-colour infrared detectors made from HgCdTe grown by Metal Organic Vapour Phase Epitaxy (MOVPE). The detectors are staring, focal plane arrays consisting of HgCdTe mesa-diode arrays bump bonded to silicon read-out integrated circuits (ROICs). Each mesa diode has one connection to the ROIC and the colours are selected by varying the applied bias. Results will be presented for both two-colour and three-colour devices. In a two-colour n-p-n design the cut-off wavelengths are defined by the compositions of the two n-type absorbers and the doping and composition of the p-type layer are chosen to prevent transistor action. The bias polarity is used to switch the output between colours. This design has been used to make MW/LW detectors with a MW band covering 3 to 5 μm and a LW band covering 5 to 10 μm. In a three-colour n-p-n design the cut-off wavelengths are defined by the compositions of the two n-type absorbers and the p-type absorber, which has an intermediate cut-off wavelength. The absorbers are separated from each other by electronic barriers consisting of wide band-gap material. At low applied bias these barriers prevent photo-electrons generated in the p-type absorber from escaping and the device then gives an output from one of the n-type absorbers. At high applied bias the electronic barrier is pulled down and the device gives an output from both the p-type absorber and one of the n-type absorbers. Thus by varying the polarity and magnitude of the bias it is possible to obtain three-colours from a two-terminal device. This design has been used to make a SW/MW/MW detector with cut-off wavelengths of approximately 3, 4 and 6 μm.

The performance of three-color HgCdTe photovoltaic heterostructure detector is examined theoretically. In comparison with two-color detectors with two back-to-back junctions, three-color structure contain an absorber of intermediate wavelength placed between two junctions, and electronic barriers are used to isolate this intermediate region. This structure was first proposed by British workers. Enhanced original computer programs are applied to solve the system of non-linear continuity equations for carriers and Poisson equations. In addition, the numerical analysis includes the dependence of absorption coefficient on Burstein effect as well as interference effects in heterostructure with metallic electrical contacts. Three detector structures with different localizations of separating barriers are analyzed. The calculations results are presented in the form of spatial distributions of bandgap energy and quantum efficiency. It is shown that the performance of the detector is critically dependent on the barrier's doping level and position in relation to the junction. This behavior is serious disadvantage of the considered three color detector. A small shift of the barrier location and doping level causes serious changes in spectral responsivity.

SMART focal plane arrays have in-pixel signal processing circuits that improve the performance of electro-optical sensors and extend their functionality. This paper describes two types of SMART focal plane array that have been developed at QinetiQ aimed at improved sensitivity and long range object identification. A novel in-pixel adaptive circuit is described which improves sensitivity by removing the background photo-signal. This allows the detector stare time to be increased resulting in lower noise bandwidth and an increase in signal-to-noise ratio. The second type of SMART focal plane array described in this paper is designed to detect time varying signals generated, for example, by helicopter blades, jet turbine engines and hot exhaust plumes. The detection of temporal signatures enables objects to be identified at significantly longer ranges than conventional focal plane arrays.

We report on processing techniques to effectively control the data bandwidth in larger format Focal Plane Array (FPA) sensors. We have developed an image processing architecture for variable acuity FPAs that give a controlled reduction in the data rate via simple circuits that estimate activity on the FPA image plane. Integrated on-FPA signal processing goals are to perform pre-processing that is usually performed downstream in a dedicated processing module. Techniques for image pre-processing described in this paper allow transmitting "active" pixel data while skipping unchanging pixels. These techniques for image pre-processing adjacent to the FPA allows significant reductions in the data rate, size, weight and power for small and low cost systems that cannot work with a large image processing.

The first generation of high performance thermal imaging sensors in the UK was based on two axis opto-mechanical scanning systems and small (4-16 element) arrays of the SPRITE detector, developed during the 1970s. Almost two decades later, a 2nd Generation system, STAIRS C was introduced, based on single axis scanning and a long linear array of approximately 3000 elements. The UK has now begun the industrialisation of 3^rd Generation High Performance Thermal Imaging under a programme known as "Albion". Three new high performance cadmium mercury telluride arrays are being manufactured. The CMT material is grown by MOVPE on low cost substrates and bump bonded to the silicon read out circuit (ROIC). To maintain low production costs, all three detectors are designed to fit with existing standard Integrated Detector Cooling Assemblies (IDCAs). The two largest focal planes are conventional devices operating in the MWIR and LWIR spectral bands. A smaller format LWIR device is also described which has a smart ROIC, enabling much longer stare times than are feasible with conventional pixel circuits, thus achieving very high sensitivity. A new reference surface technology for thermal imaging sensors is described, based on Negative Luminescence (NL), which offers several advantages over conventional peltier references, improving the quality of the Non-Uniformity Correction (NUC) algorithms.

In order to fully exploit emerging 3rd generation infrared detector technology, very high performance signal processing electronics are required in order to process in real-time, the vast amount of data that can be generated. This paper describes SELEX Sensors and Airborne System's most recent developments based upon the existing Sensor Integrated Modular Architecture (SiGMA) thermal imager. The key advances described in this paper include a modular architecture approach allowing physical separation of the processing core from the detector and proximity electronics, the miniaturisation of the processing electronics and the introduction of a solid state micro-scan mechanism which builds upon concepts developed during the company's previous work with uncooled infrared detector technology. The sensor architecture is initially designed to operate with the SELEX S&AS developed Hawk infrared detector, a medium waveband 640*512 element CMT array on a 16 micron pitch, but will also be compatible with the emerging Albion detector arrays, a medium waveband 1024*768 element CMT array on a 16 micron pitch and a long waveband 640*512 element CMT array on a 24 micron pitch. Other areas described are the development of advanced image processing algorithms including non-linear correction for display optimisation.

This presentation will review some of the work on range gated imaging undertaken at the Swedish Defence Research Agency (FOI). Different kind of systems covering the visible to 1.5 μm region have been studied and image examples from various field campaigns will be given. Example of potential applications will be discussed.

The next generation of IR sensor systems will include active imaging capabilities. One example of such a system is a gated-active/passive system. The gated-active/passive system promises long-range target detection and identification. A detector that is capable of both active and passive modes of operation opens up the possibility of a self-aligned system that uses a single focal plane. The detector would need to be sensitive in the 3-5 μm band for passive mode operation. In the active mode, the detector would need to be sensitive in eye-safe range, e.g. 1.55 μm, and have internal gain to achieve the required system sensitivity. The MWIR HgCdTe electron injection avalanche photodiode (e-APD) not only provides state-of-the-art 3-5 μm spectral sensitivity, but also high avalanche photodiode gain without minimal excess noise. Gains of greater than 1000 have been measured in MWIR e-APDs with a gain independent excess noise factor of 1.3. This paper reports the application of the mid-wave HgCdTe e-APD for near-IR gated-active/passive imaging. Specifically a 128x128 FPA composed of 40 μm pitch, 4.2 μm to 5 μm cutoff, APD detectors with a custom readout integrated circuit was designed, fabricated, and tested. Median gains as high as 946 at 11 V bias with noise equivalent inputs as low as 0.4 photon were measured at 80 K. A gated imaging demonstration system was designed and built using commercially available parts. High resolution gated imagery out to 9 km was obtained with this system that demonstrated predicted MTF, precision gating, and sub 10 photon sensitivity.

Range-gated or burst illumination systems have recently drawn a great deal of attention concerning the use for target classification. The development of eye-safe lasers and detectors will make these systems ideal to be combined with thermal imagers for long range targeting at night but also for short range security applications. This presentation will describe performance modelling and simulation of range-gated systems and discuss these together with experimental data.

In this communication we report high performance gain characteristics measured at T=77K in electron injected MW HgCdTe APDs. A full set of characterisations, including gain, excess noise, dark current and first measurement of the impulse response, was performed on test arrays of backside illuminated pin type MW APDs, manufactured at CEA LETI using an MBE grown HgCdTe absorption layer. A record high avalanche gain of M=5300 have been demonstrated in these diodes, associated with a low noise factor, F=1.0-1.3, and low dark current. The sensistivity of the APD is discussed in terms of the impact of the distribution of the gain in the structure for different applications and we have estimated a shot noise equivalent input current, Ieq_in=2.0 10^-13 to 1.0 10^-12A, for continuous measurements, and a dark count rate for photon counting applications DCR=2.7 10⁶ s^-1. The first measurements of the impulse response of the MW HgCdTe APDs showed that the band width was only weakly dependent on the gain, in coherence with the dominant electron multiplication evidenced by the low value of the noise factor. At the maximum gain, M=5000, we measured a risetime of t_10-90=88ps and a fall time of t_90-10=2.4ns, yielding a record high band width product of GBW=723GHz (BW=145MHz), mainly limited by the diffusion and life time of the minority electrons.

Raytheon is developing HgCdTe APD arrays and sensor chip assemblies (SCAs) for scanning and staring LADAR systems. The nonlinear characteristics of APDs operating in moderate gain mode place severe requirements on layer thickness and doping uniformity as well as defect density. MBE based HgCdTe APD arrays, engineered for high performance, meet the stringent requirements of low defects, excellent uniformity and reproducibility. In situ controls for alloy composition and substrate temperature have been implemented at HRL, LLC and Raytheon Vision Systems and enable consistent run to run results. The novel epitaxial designed using separate absorption-multiplication (SAM) architectures enables the realization of the unique advantages of HgCdTe including: tunable wavelength, low-noise, high-fill factor, low-crosstalk, and ambient operation. Focal planes built by integrating MBE detectors arrays processed in a 2 x 128 format have been integrated with 2 x 128 scanning ROIC designed. The ROIC reports both range and intensity and can detect multiple laser returns with each pixel autonomously reporting the return. FPAs show exceptionally good bias uniformity <1% at an average gain of 10. Recent breakthrough in device design has resulted in APDs operating at 300K with essentially no excess noise to gains in excess of 100, low NEP <1nW and GHz bandwidth. 3D LADAR sensors utilizing these FPAs have been integrated and demonstrated both at Raytheon Missile Systems and Naval Air Warfare Center Weapons Division at China Lake. Excellent spatial and range resolution has been achieved with 3D imagery demonstrated both at short range and long range. Ongoing development under an Air Force Sponsored MANTECH program of high performance HgCdTe MBE APDs grown on large silicon wafers promise significant FPA cost reduction both by increasing the number of arrays on a given wafer and enabling automated processing.

We report fast and sensitive long (10 μm) wavelength photodetectors operating at near room temperature. The devices are based on HgCdTe multilayer heterostructures grown by MOCVD on (211) and (111) GaAs substrates. Device-quality heterostructures are obtained without any post growth anneal. The recent improvements of MOCVD growth were: optimized design of the device architecture to increase speed of response, better IMP growth parameters selection taking into account interdiffusion time changes during growth, stoichiometry control during growth by the layer anneal at metal rich vapors during each IMP cycle, precursor delivery to the growth zone monitored with IR gas analyzer, additional metal-rich vapor anneal at the end of growth and passivation of detector structures with wide gap HgCdTe overgrowth deposition. Monolithic optical immersion of the detectors to GaAs microlenses has been applied in purpose to improve performance and reduce RC time constant. The response time of the devices have been characterized using 10μm quantum cascade laser, fast oscilloscope with suitable transimpedance amplifier as a function of detector design, temperature and bias. Detectivity of the best thermoelectrically cooled optically immersed photodiodes approaches 1⋅10¹⁰ cmHz^1/2/W at ≈10 μm wavelength. The response time of small area decreases with reverse bias to response achieving <100 ps with weak reverse bias.

A dual-band IR camera system based on a dual-band QWIP focal plane array in 384x288x2 format was developed. The camera delivers exactly pixel-registered simultaneously acquired images and exhibits an excellent NETD of <30 mK at an integration time of less than 10 ms. It is equipped with Camera Link and Gigabit Ethernet data interface and is connected to and operated from a personal computer. The camera is equipped with a special dual-band, dual-field-of-view lens (14.6 degree and 2.8 degree diagonal FOV). Radiometric calibration was performed for real quantitative comparison of MWIR and LWIR radiant power. The system uses special software to extract and visualize the - often quite small - differences of MWIR and LWIR images. The software corrects and processes the images and permits to overlay them with complementary colors such that differences become apparent and can easily be perceived. As a special feature, the system has advanced software for real-time image processing of dynamic scenes. It has an image stabilization feature which compensates for the movement of the camera sensor relative to the scene observed. It also has a powerful image registration capability for automatic stitching of live images to create large mosaic images. The camera system was tested with different scenes and under different weather conditions. It delivers large-format sharp images which reveal a lot of details which would not be perceptible with a single-band IR camera. It permits to identify materials (e.g. glass, asphalt, slate, etc.), to distinguish sun reflections from hot objects and to visualize hot exhaust gases.

Agiltron has produced a 280x240 photomechanical sensor array with an optical readout incorporating visible light cameras for both MWIR and LWIR imaging at speeds up to 1,000 frames per second. The photomechanical sensor is essentially a transducer that converts the image-induced temperature change into a mechanical deflection actuated by a micro-cantilevered beam. This defection is measured by an optical readout and converted into an electronic image. The photomechanical sensor requires no external drive for operation and therefore creates no bottleneck for readout data rate. It operates uncooled at widely varying ambient temperature. The use of off-the-shelf high speed visible light sensors allows for high frame rate imaging with no need for custom electronics or ROIC. Results on detection of rapid occurrence events, such as gunfire and rocket travel, are reported. The influence of detector sensitivity and time constant on the experimental imaging is discussed. Analysis of the frequency response of the photomechanical sensor is presented.

MEMS thermal transducers offer a promising technological platform for uncooled IR imaging. We report on the fabrication and performance of a 256x256 MEMS IR FPA based on bimaterial microcantilever. The FPA readout is performed using a simple and efficient optical readout scheme. The response time of the bimaterial microcantilever was <15 ms and the thermal isolation was calculated to be < 4x10^-7 W/K. Using these FPAs we obtained IR images of room temperature objects. Image quality is improved by automatic post-processing of artifacts arising from noise and non-responsive pixels. An iterative Curvelet denoising and inpainting procedure is successfully applied to image output. We present our results and discuss the factors that determine the ultimate performance of the FPA. One of the unique advantages of the present approach is the scalability to larger imaging arrays.

This paper reports on the development of small pixel pitch infrared FPAs based on the capacitively read bimorph microcantilever sensor technology. The heat sensing bimorph microcantilever structures are fabricated directly onto the CMOS control and amplification electronics to produce a high performance, low cost imager that is compatible with standard silicon IC foundry processing and materials. Positional responsivities of greater than 0.3 μm/K have been modeled and measured for 50 μm pitch pixels, corresponding to a temperature coefficient of capacitance, &Dgr;C/C, (equivalent to TCR for microbolometers) above 30%/K. This responsivity, along with noise capacitances in the sub-attofarad range and nominal sensor capacitances of 15 fF, give modeled NEDT < 20 mK for these devices. At smaller pixel pitches, the positional responsivity decreases rapidly with feature size resulting in increased system NEDTs. Modeling the performance of microcantilever based IR sensors with innovative sensor structures and pixel pitches down to 17 μm indicates NEDTs < 20 mK and thermal time constants in the 5 msec range, are feasible with this technology. Results from detailed thermo-electro-opto-mechanical modeling of the operation of the 25 μm pitch pixels are presented.

The use of a patterned resistive sheet acting as an infrared frequency-selective absorber is discussed. These patterned resistive sheets are a modified form of classical Salisbury Screens that utilize a resistive absorber layer placed a quarter-wavelength in front of a mirror. In contrast with previously designed planar antenna-coupled microbolometers that consist of both resistive and highly conductive metal strips (acting as antennas), the absorption layer in these structures involves a single resistive layer with patterned holes.

Multicolor capabilities, high detectivity, and quick response are highly important for advanced infrared sensor systems. Photodiodes made of narrow-band semiconductors are widely used in such applications. However, the photodiodes require cryogenic temperatures and are expensive. Less expensive uncooled bolometric detectors are less sensitive, significantly slower, and have no multicolor capability. In order to overcome abovementioned obstacles, we have been developing infrared detectors consisting of a dielectric rod antenna (DRA) in conjunction with a nanoscale metalinsulator- metal (MIM) tunnel diode. In these assemblies, the DRA amplifies the incident electromagnetic radiation, and the induced infrared frequency voltage is rectified by the MIM diode connected between the DRA and the ground electrically conductive plate, thus transforming the electromagnetic energy into a useful electrical signal. Because of the antenna's directional selectivity and using an MIM diode having the extremely low tunneling time and nanometer size contact area, such a detector can respond at terahertz frequencies at room temperature. It has been shown that DRAs made of high resistivity silicon posses low loss and enhanced gain at long infrared wavelengths. The proposed approach demonstrates the inherent benefits of a nanoscale device manufacturing technique that is compatible with existing CMOS technology, which may lead to the design of low cost sensors and/or sensor arrays for use in military and commercial applications.

Nanometer high performance InP Schottky detectors are scaled to IR wavelengths. The increased cutoff frequency of the Schottky detector was accomplished by both reducing its capacitance to attofarad range and also by reducing the contact resistance. The Schottky detectors were fabricated on InGaAs/InP substrates with the doping level as high as 1 x 10¹⁹ cm^-2. The typical Schottky detector anode size was 0.1 x 1 μm². Planar broadband antennas were designed for LWIR wavelengths to couple the radiation into the nanometer size detector. Several different IR antenna designs were evaluated, including complimentary square spirals, bow ties and crossed dipoles. A 6 × 7 array of antenna-coupled Schottky detectors was characterized at DC, yielding a 20 KΩ zero-bias resistance and a responsivity of 6 A/W for the entire array. The arrays were characterized at 2.5 THz, as well as in the IR (3-5μm and 10.6 μm). The current results for polarization sensitivity confirm that an antenna-coupled mechanism is responsible for the measured responsivity with the highest value measured at the THz range.

Thermal noise of quantum IR detectors is defined by the number of thermal carriers with energy higher or equal to the detector's energy threshold. The energy distribution function of these carriers is of Boltzmann-type with a high energy tail dictated solely by the device temperature. Therefore, thermal noise in such detectors can be suppressed only by cooling the device down. Sirica presents new technology for tunable quantum IR detector that requires no cooling. The detection is based on the response of non-equilibrium free carriers to IR photons. Sirica's IR detector uses pumping light (NIR/Visible) to form a steady-state non-equilibrium distribution (SNED) of free carriers with a narrow high-energy tail (i.e. low effective temperature), which is then used to absorb and detect IR photons. Simulations of the SNED formed in the case where the free carrier's lifetime is shorter than their energy relaxation time is presented, showing that the free carriers' effective temperature, is significantly lower than the device temperature. Although the total number of carriers in the SNED formed is small, IR photon absorption coefficient in Sirica's detector is very high (equivalent to MCT). This is due to the very high effective cross-section achieved in Sirica's proprietary detector substance. Parameters of this composite structure will be discussed.

A new low-cost long-wavelength infrared bolometer camera system is under development. It is designed for use with an automatic vision algorithm system as a sensor to detect vulnerable road users in traffic. Looking 15 m in front of the vehicle it can in case of an unavoidable impact activate a brake assist system or other deployable protection system. To achieve our cost target below €100 for the sensor system we evaluate the required performance and can reduce the sensitivity to 150 mK and pixel resolution to 80 x 30. We address all the main cost drivers as sensor size and production yield along with vacuum packaging, optical components and large volume manufacturing technologies. The detector array is based on a new type of high performance thermistor material. Very thin Si/SiGe single crystal multi-layers are grown epitaxially. Due to the resulting valence barriers a high temperature coefficient of resistance is achieved (3.3%/K). Simultaneously, the high quality crystalline material provides very low 1/f-noise characteristics and uniform material properties. The thermistor material is transferred from the original substrate wafer to the read-out circuit using adhesive wafer bonding and subsequent thinning. Bolometer arrays can then be fabricated using industry standard MEMS process and materials. The inherently good detector performance allows us to reduce the vacuum requirement and we can implement wafer level vacuum packaging technology used in established automotive sensor fabrication. The optical design is reduced to a single lens camera. We develop a low cost molding process using a novel chalcogenide glass (GASIR®3) and integrate anti-reflective and anti-erosion properties using diamond like carbon coating.

In this paper we present a comprehensive calculational model for the noise equivalent temperature difference (NETD) of infrared imaging systems based on uncooled bolometer arrays. The NETD model is validated and benchmarked using published performance data of state-of-the-art uncooled infrared bolometer arrays. The calculational model is used to evaluate possible infrared sensor and system design tradeoffs that allow optimization for low-cost infrared systems with improved reliability and lifetime, while still achieving a NETD of about 150 mK, required for pedestrian injury mitigation systems. We propose an approach in which high performance crystalline semiconductor materials with very low 1/f-noise properties and a temperature coefficient of resistance (TCR) of 3 %/K are used as thermistor material for the bolometers. The resulting increased bolometer performance can be used to operate the infrared imaging arrays in a vacuum atmosphere with increased gas pressure while still achieving useful NETD levels. The proposed calculational model suggests that a NETD on the order of 150 mK can be reached with uncooled infrared bolometer arrays operating in vacuum pressures on the order of 6 mbar. Such specifications for the bolometer vacuum package dramatically simplify wafer-level vacuum packaging and ease long-term reliability issues, contributing to lowering the vacuum packaging and thus, the overall infrared imaging chip costs.

Carbon nanotubes (CNTs) have a potential to be efficient infrared (IR) detection materials due to their unique electronic properties. The ballistic electronic transport property makes the noise equivalent temperature difference smaller compared to other semiconducting materials. In order to explore this potential application, CNT based IR detectors are fabricated by depositing the CNTs on the substrate surface and then aligning them using the Atomic Force Microscopy (AFM) based nanomanipulation system. Normally semicnoductive CNT forms a Schottky barrier with the contact metal. The photogenerated electron-hole pairs within the Schottky barrier are seperated by an external electric field or the built-in field, producing a photocurrent. This paper will focus on the performance evaluation and analysis for the CNT based IR detectors. Experiments were carried out to investigate the photoresponse of single carbon nanotube based IR detectors. Based on the experimental results, the detectivity D* and the quantum efficiency are calculated and analyzed. The MWNT IR detector has a quantum efficiency of 0.313, which is much larger than the reported values of SWNTs. And the SWNT IR detector has a quantum efficiency of 0.01, which is consistent with the reported values. Both MWNT and SWNT show a low detectivity. The analysis shows that the performance of CNT based IR detectors can be further improved by using asymmetric contacts instead of symmetric contacts.

By adopting new capacitance reading scheme, a capacitive type uncooled infrared detector structure with high fill-factor and effectively controllable thermal conductance is proposed. Instead of conventional MEMS capacitor structure (i.e. an insulating gap between top and bottom electrodes), a capacitor with a floating electrode and two bottom electrodes has been applied to the infrared detector. Infrared absorber which also acts as the floating electrode of the capacitor is connected to the substrate via two bimaterial legs. These legs consist of two materials having large difference in thermal expansion coefficient (Al: 25ppm/K and SiO₂: 0.35ppm/K), so that the legs are deflected according to the certain temperature change due to the infrared absorption. This leg's movement results in the displacement of the top electrode of the capacitor, and infrared is sensed by measuring the capacitance change. However, the one end tip of the bimaterial leg does not contain Al and consist of SiO₂, solely. This leg design enables the absorber to be separated from the substrate thermally as well as electrically, because insulators usually have low thermal conductivity than metals more than an order. The capacitance change by the result of infrared absorption is read only through two bottom electrodes which are placed right under the absorber, and also perform as infrared reflectors. The design has advantages of enlarging fill-factor of the infrared detector, effective thermal conductance controlling and high sensitivity to IR. With only small dimensions of SiO₂ (10μm x 2μm x 0.2μm), the device can have low thermal conductance of 1.3x10^-7W/K, so that the portion of the legs can be reduced in a pixel area. The device has fill-factor of 0.77 and 14%/K of sensitivity to infrared rays concerning 1~2K of temperature difference between the structure and the substrate.

The Thermal Light Valve™ (TLV) is a diffractive thin film spatial light modulator that provides high response to long-wavelength infrared radiation. In this paper we describe the rationale for optical-readout thermal imaging arrays, and some of the challenges faced by past devices. We then describe the TLV device, its solid state structure, readout system configuration, and performance parameters. We show how the TLV overcomes key performance issues faced by previous optical-readout arrays to achieve a modeled system performance of 16mK NETD. In addition we describe the TLV's advantages from the point of view of manufacturing tolerances and wide ambient temperature operating ranges resulting in a TLV chip yield in excess of 95% - a critical cost advantage of RedShift Systems' OpTIC™ optical thermal imaging cores.

Passive infrared (PIR) security sensors employ decades old pyroelectric technology for short range detection. This ubiquitous technology serves a major market which receives little attention in the international IR forum. It is, however, a market ripe for exploitation using modern IR sensor technology. In this paper a review will be made of various IR technologies, as applied to this application. It will be reasoned that three competing technologies have the potential to be successful in the short term: silicon resistance and diode microbolometers (two options of the former). An update will also be given on the development at Electro-optic Sensor Design (EOSD) of amorphous silicon microbolometer security sensor technology employing non-evacuated packaging and plastic optics. Establishment of a new generation PIR security sensor technology also paves the way for high performance low cost IR sensors for numerous short range applications.

The authors have successfully developed versatile uncooled infrared sensor modules, which have the dual dynamic range drive (DDRD) feature enabling both a wide object temperature range and a high temperature resolution and are applicable to a variety of uses. These modules allow users to get not only thermal images of room temperature objects at a high temperature resolution but also those of high temperature objects. The sensor driven by the modules is of the bolometer type having the pixel pitch of 23.5um, which may be the smallest pitch among commercial uncooled sensors in the world. The article describes the characteristics and performance of the modules and introduces the DDRD feature.

This paper presents the recent progress at ULIS to reduce IR-FPA integration cost for camera manufacturers. The inherent wide offset and responsivity spread of classical uncooled infrared focal plane arrays, leads to complex compensation electronics, making camera integration far more complex and expensive. ULIS low dispersion a-Si:H focal plane arrays (FPAs) address already this issue by offering wide dynamic range, low NETD and low cost with no extra custom components. ULIS continues his effort towards even lower signal dispersion. Within this scope, this paper reviews the latest development at ULIS of low dispersion FPA integrated readout circuits and FPA-integrated tools enabling camera manufacturers to improve the image quality.

Thermal imaging market is today more and more attracted by systems with "instant-on" and low power consumption. Therefore the "TECless" operation of uncooled microbolometer detectors, that is where no Peltier module is needed, is the major step to fulfill the market requirement. In order to fulfill this trend, LETI/SLIR is working on a new IRCMOS architecture. This new design is based on a differential reading implemented with current mirrors that simultaneously reduces focal plane temperature sensitivity and simplifies the detector driving. An IRCMOS prototype (320 x 240 with a pitch of 25 &mgr;m) has been designed, processed, and characterized. This paper presents an overall view of this new design and the preliminary characterization results got from this focal plane array.

BAE Systems has developed an advanced 640 x 480 focal plane array (FPA) with a 17 &mgr;m pixel pitch. Sensitivity of ≤ 50 mK was demonstrated and the FPAs were used in imaging demonstrations. Successful scaling of BAE Systems' patented single contact per pixel, single-level microbolometer process to 17 &mgr;m pitch provides a path toward next generation microbolometer imaging systems.

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 and mass production oriented. This new 25 μm pixel design benefits from a higher pixel thermal insulation while keeping low thermal time constant. Furthermore, we developed this new 25 μm version on the basis of the well mastered 35 μm pixel-pitch technology. Thanks to this new pixel design and by pushing the design rules even further, a high fill factor has been kept, without the use of a complex, as well as an expensive, two-level structure. The detector is described in terms of readout integrated circuit (ROIC) architecture, packaging, operability and electro-optical performances. A new read out integrated circuit structure has been designed specifically for this detector. High level functions like gain, image flip and integration time could be operated through a serial link to minimize the number of electrical interconnections. In addition, a small LCC package has been developed enabling mass production dedicated to compact hand held or helmet mounted cameras.

LETI has been involved in IRFPA development since 1978, the design department (LETI/DCIS) has focused its work on new ROIC architecture since many years. The trend is to integrate advanced functions into the CMOS design in the aim of making cost efficient sensors. The purpose of this paper is to present the latest developments of an Analog to Digital Converter embedded in a 25μm pixel. The design is driven by several goals. It targets both long integration time and snapshot exposure, 100% of image frame time being available for integration. All pixels are integrating the IR signal at the same time. The IR signal is converted into digital by using a charge packet counter. High density 130nm CMOS allows to use many digital functions such as counting, memory and addressing. This new structure has been applied to 25μm pitch bolometer sensors with a dedicated 320 x 240 IRCMOS circuit. Due to smart image processing in the CMOS, the bolometer architecture requirements may become very simple and low cost. The room temperature sensitivity and the DC offset are solved directly in the pixel. This FPA targets low NETD (<50mK), a variation of 80 Kelvin for the FPA temperature, 14 bits output at 50/60Hz video rate.

SCD has established an uncooled detector product line based on the high-end VO_x μ-bolometer technology. The first PFA launched was BIRD384, a 384x288 (or 320x240) configurable format with 25μm pitch. Typical NETD values for these FPAs are below 50mK with an F/1 aperture and 60 Hz frame rate. The product exhibits superior image uniformity, stability and reduced power consumption, making it most suitable for a broad range of "high-end" military and commercial applications. In this paper we report on our progress in development of new products in accordance with SCD's uncooled products roadmap: 1. A "sensitive" version of BIRD384 with an improved NETD of ~ 30mK @ F/1, 60Hz frame rate. This performance is achieved by optimizing concurrently the membrane structure, pixel architecture and ROIC electronics. 2. An improved version of BIRD384 ROIC that supports 100/120Hz frame rate and high dynamic range ("Fire Man" option). 3. First data of the BIRD640 - a 640x480 array with 25μm pitch and NETD ≤ 50mK @ F/1, 60Hz frame rate.

DRS is a major supplier of the 25μm pixel pitch 640x480 and 320x240 infrared uncooled focal plane arrays (UFPAs) and camera products for commercial and military markets. The state-of-the-art 25μm pixel focal plane arrays currently in production provide excellent performance for soldier thermal weapon sights (TWS), vehicle driver vision enhancers (DVE), and aerial surveillance and industrial thermograph applications. To further improve sensor resolution and reduce the sensor system size, weight and cost, it is highly desired to reduce the UFPA pixel size. However, the 17μm pixel FPA presents significant design and fabrication challenges as compared with 25μm pixel FPAs. The design objectives, engineering trade-offs, and performance goals will be discussed. This paper presents an overview of the 17μm microblometer uncooled focal plane arrays and sensor electronics production and development activities at DRS. The 17 μm pixel performance data from several initial fabrication lots will be summarized. Relevant 25μm pixel performance data are provided for comparison. Thermal images and video from the 17μm pixel 640x480 UFPA will also be presented.

RVS has made a significant breakthrough in the development of a 640 x 512 uncooled array with a unit cell size of 17 μm x 17 μm, and performance approaching that of the 25μm arrays. The successful development of this array is the first step in achieving mega-pixel formats. This FPA is designed to ultimately achieve performance of (<50mK, f/1, 30 Hz) with an 8 msec time constant. The SB-400 is a highly productized ROIC and is designed to achieve very good sensitivity (low NETD and low spatial noise) and good dynamic range. The improved performance is through bolometer structure improvements and an innovative ROIC design. It also has a simple and flexible electrical interface which allows external electronics to be small, lightweight, low-cost, and low-power. Almost all adjustments can be made through the serial interface; hence there is no need for external adjustable (DAC) circuitry. The improved power supply rejection helps maintain highly stable detector and strip resistor bias voltages which helps reduce spatial noise and image artifacts. The combination of reduced FPA pixel size and improved effective thermal sensitivity enhances weapon sight performance by providing smaller, lighter-weight sights via reduced optics size or increased range via enhanced pixel resolution without increasing mass or increased range via improved NETD (lower f/#) without increasing mass. We will also provide an update on the enhanced performance and yield producibility of our NVESD ManTech 640 x 480 25μm arrays. We will also show the improvement in our uncooled common architecture electronics in terms of reduced power and size for helmet and rifle mounted sensors and a variety of missile applications.

Paradoxically more than 50 years after being used in WWII, polycrystalline PbSe technology has turned today into an emerging technology. Without any doubt one of the main facts responsible for the PbSe resurgence is a new method for processing detectors based on a Vapour Phase Deposition (VPD) technique developed at CIDA. Using this method, the first low density 2D PbSe Focal Plane Array (FPA), an x-y addressed type device, was processed on silicon. Even though the last advances have been important they are not yet enough to consider this technology as a real alternative to other uncooled technologies. To reach technical relevance and commercial interest it is obligated to integrate monolithically or hybridize the sensors with their corresponding read out electronics (ROIC). Aiming to process monolithic devices, a proper CMOS read out electronics were designed. In parallel, enabled technologies were developed for adapting the material peculiarities to the CMOS substrates. In this work, the first monolithic device of VPD PbSe is presented. Even though it is a modest 16x16 FPA with a pitch of 200 μm, it represents an important milestone, allocating polycrystalline PbSe among the major players in the short list of uncooled IR detectors. Unlike microbolometers and ferroelectrics, it is a photonic detector suitable for being used as a detector in low cost IR imagers sensitive to the MWIR band and with frame rates as high as 1000 fps. The number of applications is therefore huge, some of them specific, unique and highly demanded in the military and security fields such as sensors applied to fast imagers, Active Protection Systems or low cost seekers.

Pixelwise integrated circuits involving a pixel-level analog-to-digital converter (ADC) are studied for 320 × 240 microbolometer focal plane arrays (FPAs). It is necessary to use the pixelwise readout architecture for decreasing the thermal noise. However, it is hard to locate a sufficiently large integration capacitor in a unit pixel of FPAs because of the area limitation. To effectively overcome this problem, a two step integration method is proposed. First, after integrating the current of the microbolometer for 32&mgr;s, upper 5bits of the 13bit digital signal are output through a pixel-level ADC. Then, the current of the microbolometer is integrated during 1ms after the skimming current correction using upper 5bits in a field-programmable gate array (FPGA), and then lower 8bits are obtained through a pixel-level ADC. Finally, upper 5bits and lower 8bits are combined into the digital image signal after the gain and offset correction in digital signal processor (DSP) Each 2×2 pixel shares an readout circuit, including a current-mode background skimming circuit, an operational amplifier(op-Amp), an integration capacitor and a single slope ADC. When the current of a microbolometer is integrated, the integration capacitor is connected between a negative input and an output of the op-Amp. Therefore a capacitive transimpedance amplifier (CTIA) has been employed as the input circuit of the microbolometer. When the output of a microbolometer is converted to digital signal, the Op-Amp is used as a comparator of the single slope ADC. This readout circuit is designed to achieve 35×35&mgr;m² pixel size in 0.35&mgr;m 2-poly 3-metal CMOS technology.

Method for equalization of temperature-induced non-uniformities in microbolometer IR FPA response based on use of variations of preliminary heating and measuring bias pulses applied both to sensitive and compensating bolometers is proposed. Carried out numerical simulation of proposed FPA architecture demonstrates high quality of signal equalization over wide temperature range that allows to apply microbolometer FPA indoors without use of any additional measures such as temperature stabilization and real-time correction.

In this paper we discuss methods to improve the geometric design of microbolometer pixels in uncooled focal plane arrays. For cost reduction reasons, the pixel pitch of these microbolometer elements should be reduced as much as possible while keeping the same level of performance. This becomes increasingly difficult once the dimensions of the microbolometer elements reach a critical value of about 25 micrometers, mainly because the available space limits the thermal isolation and the available area for IR absorption. For these reasons it is essential to optimize not only the material properties but also the geometric aspects of the microbolometer structure to get the maximum performance for a given size of the elements. Extending the work of Liddiard, in the first part of this paper we discuss the design of the optical cavity, focussing mainly on the influence of the sacrificial layer thickness, which defines the properties of the resulting Fabry Perot resonator. In the second part of this paper we concentrate on the geometry of the absorbing membrane itself and give estimates for optimum film thickness and lateral dimensions.

NETD is not the sole parameter to characterize microbolometer array and other parameters are as important as this one, indeed when a products comparison is done, NETD values but not, systematically, technology data (such as thermal time constant&ellip;) and typical imager parameters can be used. However, as NETD is strongly dependant on the thermal time constant, it's important to compare microbolometer in the same conditions to evaluate advantages and drawbacks. This paper deals with the important parameters to compare microbolometer devices and propose a figure of merit to take into account thermal sensitivity as well as imager characterization: such as MTF, fill factor and thermal time constant, which are often forgotten in the data products; for example, a die with a NETD around 10mK and thermal time constant around 40ms will not be compliant with a 100 Hz frame rate and has to be compared with a 40mK, &tgr;=10ms component. The important point is to compare the right criteria and to make the best choice for the application. An example will be also presented to see how to choose an uncooled array for a given application.

Umicore, known for its activities in the infrared materials and molded optics, this year launches a new infrared glass called GASIR® 3. This material can be molded using Umicore's proprietary molding technology and allows serving a wide range of new markets. Examples are a new automotive commercial application and sensing applications with their need for very small optics. Parallel to the materials development, a new coating has been developed by Umicore that allows the use of GASIR® molded optics in extremely harsh environments. The extreme performance of this new type of coating which complies with the toughest military specs will also be described.

Very long range surveillance and target recognition applications in the infrared spectral range require optical lens systems with large focal length and high numerical aperture optimized for low aberrations and stray light at a working temperature considerably different from the temperature of mounting and adjustment of the system. Additionally, for the airborne use the system shall be rugged, lightweight and compact. These conflicting requirements do not only represent a demanding design task. The much bigger challenges consist in the selection and characterisation of the optical material, in the fabrication and measurement of the particular optical elements, in their integration into the lens system as well as in the characterisation of this lens system and in the verification of its performance parameters. Recent technological approaches developed at JENOPTIK Laser, Optik, Systeme GmbH for the fabrication and the test of such lens systems will be presented in this paper. It will be shown that an iterative combination of manufacturing and measurement techniques is needed for the fabrication of IR lens systems meeting the highest performance requirements.

Increasing demands for thermal imaging systems on unmanned aerial vehicles have led to a concentrated effort in the design and development of light weight infrared optical systems. Pre-engineered or commercially available infrared lens assemblies are typically unsuitable for such low mass and volume constrained applications. This paper will focus on the challenging aspects and design considerations employed to minimize the weight of the refractive elements as well as the associated opto-mechanical support housings. In particular, consideration will be directed towards the hurdles associated with the manufacture of systems intended to operate in this unique branch of surveillance optics.

In a traditional optical system the imaging performance is maximized at a single point in the operational space. This characteristic leads to maximizing the probability of detection if the object is on axis, at the designed conjugate, with the designed operational temperature and if the system components are manufactured without error in form and alignment. Due to the many factors that influence the system's image quality the probability of detection will decrease away from this peak value. An infrared imaging system is presented that statistically creates a higher probability of detection over the complete operational space for the Hotelling observer. The system is enabled through the use of wavefront coding, a computational imaging technology in which optics, mechanics, detection and signal processing are combined to enable LWIR imaging systems to be realized with detection task performance that is difficult or impossible to obtain in the optical domain alone. The basic principles of statistical decision theory will be presented along with a specific example of how wavefront coding technology can enable improved performance and reduced sensitivity to some of the fundamental constraints inherent in LWIR systems.

Space based HgCdTe imaging devices, built on CdZnTe substrates, require radiation hardened anti-reflection (AR) treatments in order to withstand the rigors of the space environment. Conventional anti-reflection (AR) coatings provide adequate optical performance but are prone to delamination and degradation due to extreme temperature cycling and irradiation in space. Consequently, there is an intense need for improved AR technology that combines high optical performance with improved durability. Etching physical gradient or motheye structures directly into the CdZnTe eliminates the need to deposit additional layers of different materials onto the substrate, avoiding the possibility of delamination and cross contamination. Motheye AR surfaces, under development at Surmet Corporation, have demonstrated excellent broadband optical performance in the LWIR (7 to14 micron) waveband. Surmet's motheye technology involves direct etching of a regular pattern of fine features into the CdZnTe substrate, using standard lithography and dry etching techniques. The results from this ongoing research and development effort are discussed.

Un-cooled microbolometer sensors used in modern infrared night vision systems such as driver vehicle enhancement (DVE) or thermal weapons sights (TWS) require a mechanical shutter. Although much consideration is given to the performance requirements of the sensor, supporting electronic components and imaging optics, the shutter technology required to survive in combat is typically the last consideration in the system design. Electro-mechanical shutters used in military IR applications must be reliable in temperature extremes from a low temperature of -40°C to a high temperature of +70°C. They must be extremely light weight while having the ability to withstand the high vibration and shock forces associated with systems mounted in military combat vehicles, weapon telescopic sights, or downed unmanned aerial vehicles (UAV). Electro-mechanical shutters must have minimal power consumption and contain circuitry integrated into the shutter to manage battery power while simultaneously adapting to changes in electrical component operating parameters caused by extreme temperature variations. The technology required to produce a miniature electro-mechanical shutter capable of fitting into a rifle scope with these capabilities requires innovations in mechanical design, material science, and electronics. This paper describes a new, miniature electro-mechanical shutter technology with integrated power management electronics designed for extreme service infra-red night vision systems.

The optical scheme of a multispectral thermal imager (MSTI) is reviewed on the basis of a staring thermal imager and interferometers set at the Brewster angle to the optical axis of the device. The calculations of a usable sensitivity, resolving power and other parameters of this device are carried out.

We report the design, fabrication and optical characterization of a step index and microstructured crystalline optical fibers from silver halide that are singlemode at 10.6 &mgr;m, the wavelength of a CO₂ laser . Optical losses measured by cutback method were about 2 dB/m. The wide transmission range of the material (wavelengths 2-20 &mgr;m) provides great potential for applications in spectroscopy and for the development of a range of new crystalline-based non-linear optical fibers. Singlemode fibers for the middle infrared may be applied in infrared systems for heterodyne detecting.

Novel tactics employed in carrying out military and antiterrorist operations call for the development of a new generation of warfare, among which sophisticated portable infrared (IR) imagers for surveillance, reconnaissance, targeting and navigation play an important role. The superior performance of such imagers relies on novel optronic technologies and maintaining the infrared focal plane arrays at cryogenic temperatures using closed cycle refrigerators. Traditionally, rotary driven Stirling cryogenic engines are used for this purpose. As compared to their military off-theshelf linear rivals, they are lighter, more compact and normally consume less electrical power. Latest technological advances in industrial development of high-temperature (100K) infrared detectors initialized R&D activity towards developing microminiature cryogenic coolers, both of rotary and linear types. On this occasion, split linearly driven cryogenic coolers appear to be more suitable for the above applications. Their known advantages include flexibility in the system design, inherently longer life time, low vibration export and superior aural stealth. Moreover, recent progress in designing highly efficient "moving magnet" resonant linear drives and driving electronics enable further essential reduction of the cooler size, weight and power consumption. The authors report on the development and project status of a novel Ricor model K527 microminiature split Stirling linear cryogenic cooler designed especially for the portable infrared imagers.

The authors summarize the results of the accelerated life testing of the Ricor type K529N 1 Watt linear split Stirling cooler. The test was conducted in the period 2003-2006, during which the cooler accumulated in excess of 27,500 working hours at an elevated ambient temperature, which is equivalent to 45,000 hours at normal ambient conditions, and performed about 7,500 operational cycles including cooldown and steady-state phases. The cryocooler performances were assessed through the cooldown time and power consumption; no visible degradation in performances was observed. After the cooler failure and the compressor disassembling, an electrical short was discovered in the driving coil. The analysis has shown that the wire insulating varnish was not suitable for such elevated temperatures. It is important to note that the cooler under test was taken from the earliest engineering series; in the later manufacturing line military grade wire with high temperature insulation was used, no customer complaints have been recorded in this instance Special attention was paid to the thorough examination of the technical condition of the critical components of the cooler interior. In particular, dynamic piston-cylinder seal, flying leads, internal O-rings and driving coil were examined in the compressor. As to the cold head, we focused on studying the conditions of the dynamic bushing-plunger seal, O-rings and displacer-regenerator. In addition, a leak test was performed to assess the condition of the metallic crushed seals. From the analysis, the authors draw the conclusion that the cooler design is adequate for long life performance (in excess of 20,000 working hours) applications.

Development of the Dual-Use Cryocooler (DUC) system has progressed substantially over the past two years, including the design, build and testing of a brassboard thermo-mechanical unit (TMU). Early design efforts were undertaken with simplicity as a goal, and as a result the brassboard TMU contained significantly less parts than typical space-level cryocoolers. Build time for the brassboard unit was extremely short, with the compressor being built in a matter of days as opposed to the more traditional timescale of weeks. The brassboard TMU was subjected to characterization testing in both horizontal and vertical orientations (to address sensitivity of the pulse-tube cold head to gravitational effects), and results from that set of tests have been correlated to the thermodynamic model. Several lessons were learned as the testing and correlation activities progressed, and improvements necessary to meet the intended performance objectives were identified for implementation in the deliverable system. Significant progress was made in terms of electronics development as well. Existing tactical assets were heavily modified for use with the DUC, including the addition of separate drive circuits for each compressor motor. The operating software was modified to enable features not found in typical tactical systems such as first-order active vibration cancellation. Ultimately, the brassboard electronics were used to drive passive loads as well as an actual (representative) tactical Stirling cryocooler.

For high performance IR detectors the split linear cooler is a preferred solution. High reliability, low induced vibration and low audible noise are major benefits of such coolers. Today, most linear coolers are qualified for MTTF of 8,000h or above. It is a strong customer desire to further reduce the maintenance costs on system level with significantly higher cooler lifetime. Increased cooler MTTF figures are also needed for IR applications with high lifetime requirements like missile warning applications, border surveillance or homeland security applications. AIM developed a Moving Magnet Flexure Bearing compressor to meet a MTTF of minimum 20,000h. The compressor has a full flexure bearing support on both sides of the driving mechanism. In the assembly process of the compressor an automated alignment process is used to achieve the necessary accuracy. Thus, side-forces on the pistons are minimized during operation, which significantly reduces the wear-out. In order to reduce the outgassing potential most of the internal junctions are welded and the use of all non-metallic components is minimized. The outline dimensions comply with the SADA2 requirements in length and diameter. Further, when operated with a 1/2" SADA type coldfinger, the cooler meets all specified performance data for SADA2. The compressor can be combined with different Stirling type coldfingers and also with the AIM Pulse Tube coldfinger, which gives increased lifetime potential up to 50,000h MTTF. Technical details and performance data of the new compressor are shown.

Thales Cryogenics is working with large effort on the extension and improvement of its full cryocooler product range for the military as well as the civil market. Due to improvements made in the last few years by most cooler manufacturers, cryocoolers are - in the defense world - more and more seen as a commodity. However, the requirements under which cryocoolers are used and the demands which users are requesting from a cryocooler such as increased reliability, shorter cooldown times, higher efficiency, lower induced vibrations and decrease in size and mass are still very challenging. With as basis his wide product portfolio Thales Cryogenics has worked extensively on the extensions and improvement of its RM cooler range and to improve the CDT and robustness of its LSF cooler range for even more stringent environmental conditions. Next to the coolers also the latest control electronics of Thales for its linear drive coolers will be presented. Apart from Stirling coolers Thales Cryogenics is also manufacturing pulse tube coolers. At present these coolers are mainly used in civil applications. Although the CDT and efficiency of pulse tube coolers are still lower compared to Stirling coolers the reduced vibration level and increased robustness of the cold finger could be beneficial for future developments with respect to sensor cooling. This paper presents the latest results of the work performed at Thales and explains the gain for the users of cryocoolers.

A Large heat lift 40 to 80K Pulse Tube Cooler (LPTC) has been designed, manufactured and tested in partnership between AL/DTA, CEA/SBT and THALES Cryogenics BV. The Engineering Model specification of 2.3 W cooling power at 50 K for 10°C rejection temperature and maximum 160 watts electrical input power has been reached. The as built model weighs 5.13 kg. The thermal and mechanical performances are presented and discussed. This work is funded by the European Space Agency (ESA/ESTEC Contract N°18433/04/NL/AR) in the frame of future Earth Observation instruments development.

Modern Infra-Red (IR) night-vision thermal imagers for reconnaissance, surveillance, recognition and targeting rely mostly on Stirling-cycle cryogenic refrigerators thanks to their high thermodynamic efficiency. Traditionally, rotary cryogenic refrigerators comprised analog temperature controllers for controlling the cold-tip temperature. These controllers usually consist operational amplifiers, comparators, resistors and capacitors. The fine-tuning of the pre-set cold-tip temperature is achieved by setting a potentiometer to a certain resistance. It is known that potentiometers are affected by environmental temperature variations, continuous exposure to extreme temperatures, and aging. Another aspect of using a potentiometer is the difficulty for the customer to change the pre-set cold tip temperature, particularly with the RICOR On-Board (patented) controllers. Even without the use of potentiometers, the accuracy and stability of the analog components are not sufficient for the increasing requirements of advanced IR detectors at various environmental temperatures, loads, and input voltages. Moreover, manufacturers of cryogenic refrigerators could improve the reliability and traceability of their products by adding various functions to the controllers. A digital temperature controller that is based on a highly integrated flash MCU could serve both goals: improve the accuracy of the cold-tip temperature, and provide with extra features aimed at improving the functionality and reliability of the refrigerators. This paper describes the various functions and advantages of an integral ("on-board") digital temperature controller that was developed in RICOR Vacuum and Cryogenic Systems.

Screening cargo to detect nuclear materials at ports, airports, train terminals and other critical installations is one of the major challenges facing the US Department of Homeland Security and similar organizations worldwide. An effective method of identifying hidden radioactive materials is the detection of Gamma rays transmitted through the cargo container. Accurate detection and identification can be only achieved using cryogenically- cooled High Purity Germanium (HPGe) detectors. A Portal detection system developed and manufactured by ORTEC Corporation contains several such cryogenically cooled sensors (see Fig 1). This paper presents the main design considerations for selection of a cryo cooler for this application where long life, reliability, operation over extreme outdoor temperatures and with a low vibration signature are the main technical drivers. The paper further discusses the different cooling alternatives and the technical challenges of achieving a minimal foot print and interchangeability.

Environmental conditions (thermal, vibrations and shocks) are key performance and reliability factors for designing IR detectors. To address these constraints Sofradir has developed specific concepts to make the IR detector more robust in stringent environmental conditions. This paper describes these design concepts that involve both the IRFPA (IR Focal Plane Array) and the cryogenics part, as well as the level of robustness that is achieved.

Compliant snubbers are the indispensable emergency component in the low-frequency vibration isolation arrangements of the sensitive electro-optic payloads undergoing frequent exposure to the harsh environmental shock and vibration. Their primary objective is to protect the payload from colliding with the surroundings and vibration mounts form bottoming and failure originated from their excessive deflection. Needless to say, the snubber operation is associated with developing high impulsive reaction forces and accelerations capable of damaging inherently shock and vibration sensitive components of electro-optic payload. Therefore, special attention needs to be paid to their optimal design aimed at minimizing the above reaction forces and acceleration subject to limitations imposed on the peak deflections of the snubber. Unfortunately, a regular approach to an optimal design of snubbers for such sensitive equipment does not seem to exist. Using the Kelvin-Voight body approach, the authors develop an analytical model of the axial collision of a lumped body with a visco-elastic snubber and make experimental substantiation of the chosen model. From analytical solution, the authors evaluate restitution ratio, peak values of the acceleration, snubber deformation and develop procedure of the optimal design. In particular, the apparent damping ratio of the snubber is 40% independently upon the approaching velocity, snubber stiffness and allowed deformation. Further, by adapting the above model of visco-elastic collision in the Matlab-Simulink environment, the authors are attempting to design the optimal snubber for the more complicated case of low frequency vibration isolated payload exposed to the gravity forces and environmental acceleration half-sine shock 20g@11ms per MIL STD 810F. The authors discuss the obtained results and practical aspects of designing and using optimal snubbers.

For the sake of weight and compactness, the enclosures of the modern portable cryogenically cooled infrared (IR) imagers are made in the form of a light metal (aluminium, magnesium, titanium) thin-walled shell, serving as an optical bench, accommodating a telescope, an optical train and an Infrared Detector Dewar Cooler Assembly (IDDCA). Such IDDCAs normally rely on miniature rotary Stirling cryogenic coolers, which are known as powerful sources of wideband vibration giving rise to the inherently lightly damped structural resonances in the imager enclosure thus causing loud structure-borne noise. This may lead to an increased range for aural detectability of forward observers who must remain undetected, potentially for long periods of time. Consequently, the aural nondetectability distance becomes one of the crucial figures of merit (along with the overall weight, battery life, imagery quality, etc) characterising the modern portable IR imager. In the novel approach, the IDDCA is mounted within the enclosure using a special silencing pad; effectively attenuating vibration export over the typical high frequency range that contains the relevant structural resonances of the enclosure. The residual noise radiation from the imager enclosure is then attenuated practically to a background level by reshaping the radiation modes thus cancelling the overall volume velocity. This is achieved by finding the "critical point" and affixing there the optimally sized correction mass. The authors report on a successful attempt to develop a cooled imager that is inaudible at greater than 10 meters (even during the cool down phase) per MIL-STD-1774D (Level II).

As is known, a cold finger of a pulse tube cryogenic refrigerator does not contain moving mechanical components and, therefore, is traditionally thought of as producing low vibration and having extended lifespan. Because of these outstanding features, such cryogenic engines are especially attractive for use in a variety of vibration-sensitive instrumentation, such as infra-red imagers, scanning electron microscopes (SEM), superconductive quantum interference devices (SQUID), etc. However, even relatively low-level vibration produced by a cold tip of a pulse tube, resulting from oscillation of a gas pressure along with a vibration transmitted from a compressor through a metallic gas transfer tube, may sometimes appear to be excessive for the above vibration-sensitive applications. By making an extensive use of the finite element analysis supported by the full-scale experimentation, the authors are attempting to identify the sources of vibration occurring in a cold tip of a pulse tube.

The German Soldier-of-the-Future ("Infanterist der Zukunft" - IdZ) programme provides three different optronic reconnaissance systems and weapon sights respectively for each infantry squad of ten soldiers. Besides the reconnaissance and targeting device (WBBG) of the squad leader and the weapon sight (WBZG) for the sniper, the so-called "Video Visier" (video visor) will be used as a new type of weapon sight for aiming and combating with the German assault rifles G36 and AG36, with the machine gun MG4 as well as with the bazooka PzF3. The video visor includes an uncooled thermal imager, a daylight camera, an eye-safe laser range finder and a digital magnetic compass with inclination sensor. Communication with the soldier-mounted central processing unit and real-time transmission of the video data (e.g. display mounted into the helmet of the soldier) is enabled by a wireless data link. In the presentation of the requirements, the philosophy and concept as well as the functionality of the video visor will be described in detail.

In December 2004 AIM started the series production of the HuntIR long range thermal weapon sight. The sight is fielded in the Germany Future Infantryman (IdZ) basic system and since that time in continuous service in various out of area missions with German participation. For very long identification ranges >1500m cooled technology still outperforms uncooled sights, even with respect to smaller size and lower weight because the typical F/1 design of uncooled systems overcompensates cooler weight for focal length >175mm. The HuntIR sight is therefore based on a cooled MWIR detection module for long range battlefield surveillance and target engagement. The device specifically is a perfect match to state of the art small arms like 0.50 cal sniper rifles or crew served weapons like the 40mm high velocity grenade machine gun (GMG) which provide engagement ranges >1500m and need an adequate sight performance beyond that. A recent modification of HuntIR was done to provide a wider field of view for improved situation awareness in urban operations and specifically to allow the engagement of the 40mm GMG in ranges between 250-1200m. The qualification tests of the sight by the German infantry were successfully completed mid 2006. To match the demand of the follow-up program IdZ-ES additional components have to be integrated. Most important are a laser range finder (LRF), 3 axis digital magnetic compass (DMC) and a wireless data link. LRF and DMC together with a highly sophisticated fire control computer provide improved first round hit probability, the DMC additionally improves the fire control in any case of steep trajectories or for pronounced ballistic trajectories to avoid any need to precisely level the GMG. This new sight is done under the brand name RangIR. An important additional feature is the interface for air burst ammunition (ABM). The optical distance is measured by the LRF, the fire control computer accurately evaluates the trajectory under the given angle, muzzle velocity, temperature and range conditions to define the time-of-flight. This fully integrated IR fire control system is available mid 2007. The development phase of the IdZES program is under contract, series deliveries expected in 2009. The RangIR will see some specific modifications for the link and a man machine interface to control the whole IdZ-ES system components ergonomically from the weapon with optimized power supply concepts to minimize the number of batteries, chargers etc.

Today armed forces of a number of countries develop land warrior integrated, modular combat systems the so called Ground Soldier System. The German version is called "IDZ-Infanterist der Zukunft". This high-technically equipped soldier will have some outstanding capabilities which are based on technical components. One of them will be a handheld multifunctional thermal observation instrument. This light weighted instrument includes a thermal imager which detects an object in 4000m, recognizes it in 3000m and identifies it in 1500m. The IR Image channel can be superposed with the visual daylight image what is taken by an integrated CCD-camera. The image is seen trough a biocular viewer on two Organic Light Emmitting Displays. With the laser range finder which works up to 4000m and the Digital Magnetic Compass it is possible to measure distances and angles and so the own and the target object's positions. This information as well as live time video sequences can be transferred wireless to the soldiers C4I-system. The instrument is based on the surveillance platform NYXUS which was developed in close collaboration with the German Bundeswehr. The NYXUS includes additionally GPS, goniometer and northfinding gyroscope which makes it a precise and irreplaceable tool for nowadays armed forces. The instrument is developed and produced by Jena-Optronik GmbH.

Sagem Defense Securite has been awarded a 800M euro contract for the French infantrymen modernisation programme. This programme covers the development, the qualification and the production of about 32 000 soldier systems to equip all the French infantry starting fielding in 2008. The FELIN soldier system provides the infantryman with an integrated system increasing dramatically the soldier capability in any dismounted close combat domains. Man remains at the centre of the system, which can interface equipments or systems already fielded and future equipments to match any customer's needs. Urban operations are carefully addressed thanks to a versatile and modular solution and a dedicated C4I system, Sagem Defense Securite is a European leader in defence electronics and takes part of this major French Army transformation programme, which will play a key role in the Info Centric Network initiatives promoted in France and other countries. This paper summarises the system solutions selected by the French Army with a focus on the networked capabilities and the optronic devices.

There is a strong desire to create narrowband infrared light sources as personnel beacons for application in infrared Identify Friend or Foe (IFF) systems. This demand has augmented dramatically in recent years with the reports of friendly fire casualties in Afghanistan and Iraq. ICx Photonics' photonic crystal enhanced^TM (PCE^TM) infrared emitter technology affords the possibility of creating narrowband IR light sources tuned to specific IR wavebands (near 1-2 microns, mid 3-5 microns, and long 8-12 microns) making it the ideal solution for infrared IFF. This technology is based on a metal coated 2D photonic crystal of air holes in a silicon substrate. Upon thermal excitation the photonic crystal modifies the emitted yielding narrowband IR light with center wavelength commensurate with the periodicity of the lattice. We have integrated this technology with microhotplate MEMS devices to yield 15mW IR light sources in the 3-5 micron waveband with wall plug efficiencies in excess of 10%, 2 orders of magnitude more efficient that conventional IR LEDs. We have further extended this technology into the LWIR with a light source that produces 9 mW of 8-12 micron light at an efficiency of 8%. Viewing distances >500 meters were observed with fielded camera technologies, ideal for ground to ground troop identification. When grouped into an emitter panel, the viewing distances were extended to 5 miles, ideal for ground to air identification.

In recent years, operations executed by naval forces have taken place at many different locations. At present, operations against international terrorism and asymmetric warfare in coastal environments are of major concern. In these scenarios, the threat caused by pirates on-board of small surface targets, such as jetskis and fast inshore attack crafts, is increasing. In the littoral environment, the understanding of its complexity and the efficient use of the limited reaction time, are essential for successful operations. Present-day electro-optical sensor suites, also incorporating Infrared Search and Track systems, can be used for varying tasks as detection, classification and identification. By means of passive electro-optical systems, infrared and visible light sensors, improved situational awareness can be achieved. For long range capability, elevated sensor masts and flying platforms are ideally suited for the surveillance task and improve situational awareness. A primary issue is how to incorporate new electro-optical technology and signal processing into the new sensor concepts, to improve system performance. It is essential to derive accurate information from the high spatial-resolution imagery created by the EO sensors. As electro-optical sensors do not have all-weather capability, the performance degradation in adverse scenarios must be understood, in order to support the operational use of adaptive sensor management techniques. In this paper we discuss the approach taken at TNO in the design and assessment of system concepts for future IRST development. An overview of our maritime programme in future IRST and EO system concepts including signal processing is presented.

Over the last decade, SCD has developed and manufactured high quality InSb Focal Plane Arrays (FPAs), that are currently used in different applications worldwide. SCD's production line includes InSb FPAs with mid format (320x256 elements), and large format (640x512 elements), all available in various packaging configurations, including fully integrated Detector-Dewar-Cooler Assemblies (DDCA). Many of SCD's products are fully customized for customers' needs, and are optimized for each application with respect to the weight, power, size, and performance. In 2006, SCD has added to its broad InSb product portfolio the new "Pelican" detector family. All Pelican detectors include a large format 640×512 InSb FPA with 15&mgr;m pitch, which is based on the FLIR/Indigo ISC0403 Readout Integrated Circuit (ROIC). Due to its small size, the Pelican FPA fits in any mid format Dewar, enabling upgrading of mid format systems with higher spatial resolution due to its good MTF. This work presents the high performance of Pelican products. As achieved in all SCD's InSb DDC's, the Pelican detectors demonstrate high uniformity and correctability (residual non uniformity less than 0.05% std/DR) and remarkable operability (typically better than 99.9%). The Pelican FPA can be integrated in various DDCA configurations as per application needs, such as light weight, low power and compact form for hand held imagers, or a rigid configuration for environmentally demanding operating and storage conditions.

The EL/L-8273/4 is a long range, multi-role, passive multi-spectral Infrared Search and Track system family for airborne and naval applications. The system are designed to assist tactical operations by supporting the platform's self defense system and by backing up collision avoidance in radio silence navigation. We describe the main features of this new 360 degrees coverage IRST design.

Dealing with military and asymmetric threats represents a key issue for any military vessel in various environment. In order to support ship's self protection, Thales has designed a new generation of naval infrared search and track (IRST) called ARTEMIS that has been selected to equip Future European Multi Roles Frigates (FREMM). ARTEMIS is a fully passive infrared surveillance system capable of automatically detecting and tracking both air and surface targets simultaneously. It is able to detect and track maneuvering and stealthy new threats as well as surface asymmetric threats. This paper describes technologies than has been introduced in ARTEMIS design (large IR FPA, original optical design, electronic stabilization, dedicated algorithms on COTS processing boards). It also describes the advantages offered by this new concept of electro-optical surveillance with fully static sensor heads compared to existing scanning solutions from a technical, operational and logistics point of view.

Since 2005, The THALES Group is successfully manufacturing TV/4 format QWIP sensitive arrays in high rate production through THALES Research and Technology. Sofradir has entered a full production of its VEGA-LW-RM4 IDDCA using a 25μm pitch, 384x288 QWIP Array which is the core of the very compact QWIP thermal imager CATHERINE-XP. Serial production of CATHERINE-XP has now started in THALES Optronique in order to meet the delivery schedule of the various programs for which it has been selected. A review of the QWIP Production status, CATHERINE-XP achievements and current programs are presented. As THALES Optronique has based its today strategy on very compact TI in order to address the largest panel of platforms and applications, THALES Optronique is working in cooperation with Sofradir and TRT on the evolutions of the product to take advantage of the new capabilities offered by QWIP technology like bi-spectral or polarimetric. The achievements of these developments are also presented

A passive IR approach for stationary system is introduced providing protection to high value infrastructure and strategic areas by detecting and warnings against fire shot from rifles, carbines, sub-machines and various other small arms - SWAD. SWAD provides protected surroundings in which it remotely detects small arms fire. By analyzing their patterns, including duration and intensity, SWAD classifies the type of weapon being used.

Following the demand for affordable, various range and light-weight protection against ATGM's, Elisra develops a cost-effective passive IR system for ground vehicles. The system is based on wide FOV uncooled bolometric sensors with full azimuth coverage and a lightweight processing & control unit. The system design is based on the harsh environmental conditions. The basic algorithm discriminates the target from its clutter and predicts the time to impact (TTI) and the target aiming direction with relation to vehicle. The current detector format is 320*240 pixels and frame rate is 60 Hz, Spectral response is on Far Infrared (8-14&mgr;). The digital video output has 14bit resolution & wide dynamic range. Future goal is to enhance detection performance by using large format uncooled detector (640X480) with improved sensitivity and higher frame rates (up to 120HZ).

The European anti-tank missile system MILAN has found wide-spread use in numerous countries. Introduced in 1974 it has since undergone several technological upgrades. We report here on the newly developed firing post MILAN ADT ("Advanced Technology") which improves the MILAN system performance substantially while maintaining all operational features to which MILAN operators are accustomed. An even further advanced version of this firing post is now under development in the frame of a range extension of the missile system dubbed MILAN ADT/ER. Being a command-to-line-of-sight system, the new MILAN ADT firing post is equipped with a missile tracking sensor which captures the missile's signature with a wide field-of-view optics and a large CMOS detector covering both gathering and guidance phase. Using adaptive windowing and sub-sampling functions combined with differential imaging modes this sensor tracks the signatures of all MILAN missile types with optimum precision, high resistance against IRCM, and improved signal-to-noise ratio over the entire flight path. An integrated thermal imager replaces the earlier ancillary TIs, MIRA and MILIS. The TI image is displayed on an internal micromonitor and projected into the eyepiece. Optimum axis harmonization between both missile tracking and sighting channels is ensured by projection of reference marks into each optical sensor path from an integrated multispectral projector. An extended range version will also be offered which takes advantage of the missile tracking sensor's enhanced responsivity and the oustanding precision of axis alignment. An integrated color TV sensor is substituted for the bulky direct view telescope, and both TI-/TV-sensor will provide two fields-of-view on the internal micromonitor for surveillance and target identification, respectively.

Infrared Search and Track (IRST) and threat warning systems are used in vehicle mounted or in fixed land positions. Migration of this technology to the man portable applications proves to be difficult due to the tight constraints of power consumption, dimensions, weight and due to the high video rate requirements. In this report we provide design details of a novel transient event detection (TED) system, capable of detection of blasts and gun shot events in a very wide field of view, while used by an operator in motion

When the field of operation of precision strike ground/air-to-ground missiles is extended to beyond-line-of-sight missions, autonomous seekers will soon encounter serious difficulties, especially with regard to low signature targets and complex scenarios. We have investigated dual-mode sensors which are conceived to overcome these specific problems by combining an imaging sensor with a semi-active laser seeker. These sensors offer non-line-of-sight target engagement with high reliability and under operator control using a laser target designator while minimizing the active exposure time for target designation by handing over the tracking process, once the passive imaging sensor has locked onto the target. For this purpose a laboratory demonstrator has been built with a standard TV-sensor and an InGaAs 4-quadrant detector mounted on a 2-axes gimbal system. Both detectors use a common objective; the focussed radiation is divided by a spectral beam splitter. The signals of the 4-quadrant detector are digitized and subsequently processed by an FPGA. If the pre-programmed laser pulse characteristic is identified, the position information is evaluated and the gimbal system activated in order to center the laser spot. Subsequently a tracker locks onto the target signature found in the imaging sensor signal. Once lock-on is confirmed the laser can be turned off automatically. We present the results of laboratory and field tests obtained with the dual-mode demonstrator. Based on these results we plan to replace the TV-sensor by an uncooled microbolometer array in the future. The design and expected performance of such a dual-mode sensor will be discussed. Keywords: dual-mode sensor, semi-active laser seeker, microbolometer array, target engagement

This paper introduces a novel adaptive algorithm for target detection in infrared search and track (IRST) system. The algorithm is proposed on the basis of robust and adaptive method that is invariant to the prior uncertainty with respect to statistical properties of cluttered background and noise. The essence of proposed algorithm is to design the detection index over two images obtained by processing the given image through the local gamma correction (LGC) and the estimation of target motion. And the detection index (DI) is obtained by the two factors which calculated relations between two images: luminance rate (LR), and contrast rate (CR). Results of simulation show that the proposed algorithm gives an enormous gain on real infrared image sequences.

A complete detection, management, and control security system is absolutely essential to preempting criminal and terrorist assaults on key assets and critical infrastructure. According to Tom Ridge, former Secretary of the US Department of Homeland Security, "Voluntary efforts alone are not sufficient to provide the level of assurance Americans deserve and they must take steps to improve security." Further, it is expected that Congress will mandate private sector investment of over $20 billion in infrastructure protection between 2007 and 2015, which is incremental to funds currently being allocated to key sites by the department of Homeland Security. Nearly 500,000 individual sites have been identified by the US Department of Homeland Security as critical infrastructure sites that would suffer severe and extensive damage if a security breach should occur. In fact, one major breach in any of 7,000 critical infrastructure facilities threatens more than 10,000 people. And one major breach in any of 123 facilities--identified as "most critical" among the 500,000--threatens more than 1,000,000 people. Current visible, nightvision or near infrared imaging technology alone has limited foul-weather viewing capability, poor nighttime performance, and limited nighttime range. And many systems today yield excessive false alarms, are managed by fatigued operators, are unable to manage the voluminous data captured, or lack the ability to pinpoint where an intrusion occurred. In our 2006 paper, "Critical Infrastructure Security Confidence Through Automated Thermal Imaging", we showed how a highly effective security solution can be developed by integrating what are now available "next-generation technologies" which include: Thermal imaging for the highly effective detection of intruders in the dark of night and in challenging weather conditions at the sensor imaging level - we refer to this as the passive thermal sensor level detection building block Automated software detection for creating initial alerts - we refer to this as software level detection, the next level building block Immersive 3D visual assessment for situational awareness and to manage the reaction process - we refer to this as automated intelligent situational awareness, a third building block Wide area command and control capabilities to allow control from a remote location - we refer to this as the management and process control building block integrating together the lower level building elements. In addition, this paper describes three live installations of complete, total systems that incorporate visible and thermal cameras as well as advanced video analytics. Discussion of both system elements and design is extensive.

Fire Service and First Responder Thermal Imaging Camera (TIC) applications are growing, saving lives and preventing injury and property damage. Firefighters face a wide range of serious hazards. TICs help mitigate the risks by protecting Firefighters and preventing injury, while reducing time spent fighting the fire and resources needed to do so. Most fire safety equipment is covered by performance standards. Fire TICs, however, are not covered by such standards and are also subject to inadequate operational performance and insufficient user training. Meanwhile, advancements in Fire TICs and lower costs are driving product demand. The need for a Fire TIC Standard was spurred in late 2004 through a Government sponsored Workshop where experts from the First Responder community, component manufacturers, firefighter training, and those doing research on TICs discussed strategies, technologies, procedures, best practices and R&D that could improve Fire TICs. The workshop identified pressing image quality, performance metrics, and standards issues. Durability and ruggedness metrics and standard testing methods were also seen as important, as was TIC training and certification of end-users. A progress report on several efforts in these areas and their impact on the IR sensor industry will be given. This paper is a follow up to the SPIE Orlando 2004 paper on Fire TIC usage (entitled Emergency Responders' Critical Infrared) which explored the technological development of this IR industry segment from the viewpoint of the end user, in light of the studies and reports that had established TICs as a mission critical tool for firefighters.

We have previously developed a SWIR microspectrometer based on monolithic integration of a parallel plate Micro- Electro-Mechanical Systems (MEMS) optical filter directly with a Hg_xCd_1-xTe-based infrared detector. The primary technical challenge in achieving the integration of a MEMS Fabry-Perot filter with the Hg_xCd_1-xTe detector is to keep the processing temperature less than 150°C, as the performance of Hg_xCd_1-xTe based photoconductors degrade at higher process temperatures. In this work we present our results to extend the operation into the 3-5 μm (MWIR) wavelength range. For our preliminary results, the MWIR microspectrometer was based on a hybrid packaging approach, fabricating the MWIR filter separately from the Hg_xCd_1-xTe detector; however the key process parameters relating to temperature control were maintained during fabrication of the MWIR filter, ensuring we can migrate this technology into an integrated solution. Linewidths of 210 nm, switching times of 20 μs and a tuning range of 900 nm have been achieved. The tuning speed is limited by squeezed film damping due to the physically narrow gap (&lgr;/2) between the Fabry-Perot mirrors.

The Submillimeter-wave and Infrared Ice Cloud Experiment (SIRICE) concept would provide global measurements of ice water path (IWP - the vertically integrated mass of ice particles per unit area), and weighted mean mass particle diameter (D_me). The SIRICE payload consists of two instruments, the Sub-millimeter/Millimeter (SM4) Radiometer, and the Infrared Cloud Ice Radiometer (IRCIR). IRCIR is a compact, low-cost, multi-spectral, wide field of view pushbroom infrared imaging radiometer. IRCIR will employ four IR sensor assemblies to produce 90° cross-track (contiguous along-track) coverage in three spectral bands with a spatial resolution of 0.6 km at nadir. Each IR sensor assembly consists of an uncooled microbolometer focal plane array (FPA), associated sensor core electronics, a stripe filter fixed at the FPA, and an IR lens assembly. A single scene mirror is used to provide two Earth view angles, as well as calibration views of space and the on-board calibration blackbody. The two Earth view angles will be used for stereo cloud height retrievals.

NASA has a serious problem with ice that forms on the cryogenic-filled Space Shuttle External Tank (ET) that could endanger the crew and vehicle. This problem has defied resolution in the past. To find a solution, a cooperative agreement was developed between NASA-Kennedy Space Center (KSC) and the U.S. Army Tank-automotive and Armaments Research, Development & Engineering Center (TARDEC). This paper describes the need, initial investigation, solution methodology, and some results for a mobile near-infrared (IR) ice detection and measurement system developed by MDA of Canada and jointly tested by the U.S. Army TARDEC and NASA. Performance results achieved demonstrate that the pre-launch inspection system has the potential to become a critical tool in addressing NASA's ice problem.

With heightened awareness of Homeland Security issues, the detection of explosive has become a pressing priority. Explosives detection is a very important task for National Security: threat compounds need to be detected on a variety of surfaces. Every surface will interact with the target compounds in a very unique manner and the degree of adhesion will vary from surface to surface. The formidable task includes development of new probes and methods for detection of concealed explosives. Fiber Optic Coupled Infrared Spectroscopy has been used as a potential technique to develop new methodologies for detection of explosives on surfaces. On one of such proposed methodologies involves a Grazing Angle Probe rendering the latter as a remote sensed, in situ and capability of detecting nanograms/cm² of the compounds. In this research a smearing technique was used for transferring the target analytes onto the substrates to be used as standards. Smearing was also used as a sample transfer method of the threat agents to target surfaces. One of the most relevant areas of investigation is to analyze 2,4,6-trinitrotoluene (TNT) on various non traditional surfaces such as plastics. The work also centered in to obtaining an optimization method where a more accurate spectrum could be obtained and a better spectroscopic preprocessing routine could be applied. A series of statistical methods can be used for quantification of TNT on plastic surfaces, among these are: peak height analysis and peak areas integration. Both of these can be coupled to Partial least squares regression, which is an extension of multiple linear regression models. Using peak areas in the range from 1380 to 1273 cm^-1, the method was found to be linear for loading concentration lower than 5.0 μg/cm². A loading concentration of 0.62 μg/cm² (620 ng/cm²) was considered as limit of quantification and 0.16 μg/cm² (160 ng/cm²) as limit of detection.

Fiber optics coupled-grazing angle probe Fourier transform infrared (FTIR) spectroscopy and infrared microspectroscopy have been used for characterization of the distribution and form of layers of some explosives deposited on stainless steel sheets. Among the explosives tested were trinitrobenzene, HMX and Tetryl. Various solvents were used to deposit the films on stainless steel slides. Isopropyl alcohol was the preferred solvent because it produced more homogeneous mass distributions of target explosives on the substrates. The film thickness, analyte distribution and the relation of thickness to infrared absorption/reflection response of these explosives were compared with those previously reported for TNT, 2,4-DNT and RDX. This comparison was used for described the general optical behavior of the explosives studied.

DRS LPE-grown SWIR, MWIR and LWIR HgCdTe material are fabricated in the High-Density Vertically Integrated Photodiode (HDVIP) architecture. Instruments manufactured for certain strategic applications have severe constraints on excess low frequency noise due to the effect the noise has on the image quality with subsequent consequences on the period of calibration. This paper will present data and analysis of excess low frequency noise in LWIR (&lgr;_c ~ 10.5 &mgr;m @ 60 K) HDVIP HgCdTe detectors. The vehicle for noise measurements is a multiplexed 320 x 6 array of 40 &mgr;m x 50 &mgr;m, 10.5 &mgr;m cutoff, HgCdTe detectors. Noise has been measured on a column of 320 detectors, at 60 K, as a function of frequency at zero and 50 mV reverse bias. Integration time for the measurement was 1.76 ms. Output voltage for the detectors was sampled every 10^th or every 100^th frame. 32,768 frames of time series data were collected for a total record length of 98 minutes. Since the total time for collecting the 32,768 time data series points is 98 minutes, the minimum frequency is 170 &mgr;Hz. Time series and Fourier transform data on individual detectors at 0 mV and 50 mV reverse bias in the dark have been studied. Examination of the detector current time series and Fourier transform curves thereof, reveal a variety of interesting characteristics: (i) time series displaying switching between four states characteristic of random telegraph signal (RTS) noise, the noise current power spectrum having Lorentzian type characteristics; (ii) time series data exhibiting slight wave-like characteristics with the noise current power spectrum being 1/f-like at low frequencies; (iii) pronounced wave-like characteristics in the time series with the noise current power spectrum being 1/f²-like at low frequencies; and (iv) time series having a mean value independent of time with the noise current power spectrum being white. The predominance of detectors examined had minimal excess low frequency noise down to ~ 10 mHz. In addition some isolated diodes had characteristics that lay between the four main types outlined above.

The two-dimensional spatial response of a pixel in SCD's back-side illuminated InSb Focal Plane Array (FPA) is measured directly for arrays with a small pitch, namely 30, 20 and 15&mgr;m. The characterization method uses a spot-scan measurement and de-convolution algorithm to obtain the net spatial response of a pixel. Two independent methods are used to measure the detector spatial response: a) direct spot-scan of a pixel with a focused beam; b) uniform illumination upon back-side evaporated thin gold coating, in which sub-pixel apertures are distributed in precise positions across the array. The experimental results are compared to a 3D numerical simulation with excellent agreement for all pitch dimensions. The spatial response is used to calculate the crosstalk and the Modulation Transfer Function (MTF) of the pixel. We find that for all three pixel dimensions, the net spatial response width (FWHM) is equal to the pitch, and the MTF width is inversely proportional to the pitch. Thus, the spatial resolution of the detector improves with decreasing pixel size as expected. Moreover, for a given optics and smaller array pitch, the overall system spatial resolution is limited more by the optical diffraction than by the detector. We show actual improved spatial resolution in an imaging system with a detector of smaller array pitch.

Designing a digital IR focal plane array (IRFPA) requires fulfilling very stringent requirements in terms of power consumption, silicon area and speed. Among the various ADC architectures like successive approximation, ramp or over-sampled converters, the best choice strongly depends on the application. We believe that sigma-delta converters, in spite of their quite high power consumption, are a promising solution for high-performance and medium size FPA, e.g. 320x240. This paper presents the design of a second-order incremental sigma-delta ADC dedicated to cooled (77K) IRFPA applications. System-level simulations used to define the modulator parameters and specify its analog building blocks are presented. Circuit design of the switched-capacitor modulator and the digital decimation filter is described. The column ADC including the filter has been implemented in a standard 0.35μm CMOS process on the basis of a 25μm pitch and lead to a total length of 3200μm. Test chips including a single ADC have been manufactured end of 2006. The first measurement results, at 77K, are presented along with perspectives and future developments. They demonstrate the following performance: 81dB Signal-to-Noise Ratio (SNR), 13 bits Effective Number Of Bits (ENOB) and 270μW power consumption at 17kSamples/s rate.

As the demand for mid wavelength infrared (MWIR) focal plane arrays (FPAs) continues to increase, the quality of InSb surfaces becomes more stringent. State-of-the art InSb contains <20 etch pits/cm² (EPD), and provides a surface suitable for rapid oxide desorption and high quality MBE growth. In order to satisfy resolution and sensitivity requirements for advanced MWIR FPA imaging systems ( 1 to 5.4 μm region @77°K), the surface and sub-surface of the material must be of excellent quality. CMP has proven to be a qualified finishing process for InSb surfaces in the fabrication of IRFPAs. However, a time consuming surface etch is universally required in the IRFPA manufacturing process. Gas cluster ion beam processing (GCIB) has been shown to significantly enhance the surface oxide desorption of both GaSb and InSb substrates for MBE growth and provides an alternate surface finish for IRFPA manufacturing. The use of GCIB may preclude the need for surface etching, thus reducing IRFPA processing time and chemical cleanup. This study examines the comparison of CMP and GCIB finishes on InSb surfaces and the effect on final IRFPA device pass rates. NF₃/O₂ dual energy GCIB surface processing was used in this study. Atomic force microscopy (AFM), cross-section transmission electron microscopy (XTEM), and rocking curve x-ray diffraction (XRD) examine the surface and subsurface InSb integrity. A comparison of pass-rates for completed IRFPAs with the CMP and GCIB surface shows the pass-rate to be the same, opening the possibility for etch step elimination.

The post correction uniformity performance of infrared 2D starring arrays is a key factor to ensure the best IR image quality at the camera level. SOFRADIR has conducted several studies to improve both the post correction uniformity performance and the correction tables stability over the time periods, the readout integrated circuit configuration and the environmental conditions. Indeed, works have been performed on the homogeneity technology deposits, on the improvement of the readout circuit linearity and on the optimization of the dewar design to reduce the parasitical fluxes. Thanks to these improvements, Sofradir offers to its customers high level post correction uniformity performances as well as excellent correction tables stability for the mid wave and long wave infrared band. Thus, the calibrations constraints are reduced at the camera level and the image quality is optimized over a large camera utilization conditions.

The detectors within an infrared focal plane array (FPA) characteristically have responses that vary from detector to detector. It is desirable to remove this "nonuniformity" for improved image quality. Factory calibration is not sufficient since nonuniformity tends to drift over time. Field calibration can be performed using uniform temperature sources but requires briefly obscuring the field-of-view and leads to additional system size and cost. Alternative "scene-based" approaches are able to utilize the normal scene data when performing non-uniformity correction (NUC) and therefore do not require the field-of-view to be obscured. These function well under proper conditions but at times can introduce image artifacts such as "ghosting". Ghosting results when scene conditions are not optimal for NUC. The scene-based approach presented in this paper estimates a correction term for each detector using spatial information. In parallel, motion estimation and texture features are used to identify frames and regions within frames that are suitable for NUC. This information is then employed to adaptively converge to the proper correction terms for each detector in the FPA.

In this paper a novel nonuniformity correction method that compensates for the fixed-pattern noise (FPN) in infrared focal-plane array (IRFPA) sensors is developed. The proposed NUC method compensates for the additive component of the FPN statistically processing the read-out signal using a noise-cancellation system. The main assumption of the method is that a source of noise correlated to the additive noise of the IRFPA is available to the system. Under this assumption, a finite impulse response (FIR) filter is designed to synthesize an estimate of the additive noise. Moreover, exploiting the fact that the assumed source of noise is constant in time, we derive a simple expression to calculate the estimate of the additive noise. Finally, the estimate is subtracted to the raw IR imagery to obtain the corrected version of the images. The performance of the proposed system and its ability to compensate for the FPN are tested with infrared images corrupted by both real and simulated nonuniformity.

This paper proposes a new resistance non-uniformity correction method for microbolometer-type uncooled thermal detector focal plane arrays (FPAs) that suffer from pixel-to-pixel resistance variation, which is conventionally corrected by applying a specific bias voltage to each detector by the use on-chip DACs. The proposed method uses the heating of the detector with electrical bias, where the detector is heated-up for a pre-determined period of time before the read-out phase. The proposed method uses only a heat-up signal source and simple digital blocks for each column, eliminating the need for DACs that occupy large area, contribute to the noise floor of the system, and dissipate extra power. The proposed method provides a detector current resolution of 14.5 nA with 9-bit digital data, which corresponds to the resolution of 12-bit DAC used in conventional methods.

In this paper, a novel high SNR readout circuit for a satellite TDI array is presented. Since an input range of an IR image for environmental satellites is broad and especially the cloud top temperature (CTT) that is important in understanding phenomena of atmosphere is quite low, the readout of low temperature signal is important in satellite applications. However, the noise resulted from a readout circuit is no longer ignorable compared to a detector shot noise at low IR radiation. Hence, an adaptive charge capacity control method is proposed in this paper for an improved SNR at low temperature. It is found that SNR is improved as much as 11dB at 200K and 90% background-limited infrared photodetection (BLIP) condition is satisfied over a total input range by simulation.