Proceedings Volume 5074

Infrared Technology and Applications XXIX

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Proceedings Volume 5074

Infrared Technology and Applications XXIX

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Volume Details

Date Published: 10 October 2003
Contents: 18 Sessions, 96 Papers, 0 Presentations
Conference: AeroSense 2003 2003
Volume Number: 5074

Table of Contents

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Table of Contents

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  • 3D Imaging/Ladar
  • Infrared in Strategic Defense
  • Toward Third-Generation Thermal Imagers I
  • Cooled FPAs and Applications I
  • Cooled FPAs and Applications II
  • Signal Processing In and Behind the FPA
  • Toward Third-Generation Thermal Imagers II
  • SWIR FPAs and Their Applications
  • Uncooled FPAs and Their Applications I
  • Uncooled FPAs and Their Applications II
  • Uncooled FPAs and Their Applications I
  • Uncooled MWIR FPAs
  • Infrared in Air and Space
  • QWIPs and Their Applications I
  • QWIPs and Their Applications II
  • Homeland Security
  • Infrared Optics
  • Advanced Technologies, Techniques, and Sensors
  • Signal Processing In and Behind the FPA
  • Poster Session
  • Cooled FPAs and Applications I
  • 3D Imaging/Ladar
  • Uncooled FPAs and Their Applications II
  • Poster Session
  • Uncooled FPAs and Their Applications I
3D Imaging/Ladar
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InGaAs/InP avalanche photodiode arrays for eye-safe three-dimensional imaging
John Christopher Dries, Tara Martin, Wei Huang, et al.
We report on recent progress in developing 2-dimensional arrays of InGaAs/InP avalanche photodiodes. Advances in compound semiconductor epitaxy and device processing technologies enable large (128x128) element focal plane arrays with breakdown voltage standard deviations < 0.3%. The uniformity in breakdown voltage simplifies readout integrated circuit designs, in that a single bias voltage may be used for all elements in the array. Each element in the array achieves responsivities greater than 10 A/W at a wavelength of 1550 nm, while maintaining dark currents less than 20 nA. The APD arrays stand to enable new cameras for such applications as three-dimensional imaging, and various other laser radar and communications systems. In particular, the improved responsivity of avalanche photodiodes over their pin photodiode counterparts can improve sensitivities by as much as 6 - 10 dB depending upon the readout integrated circuit bandwidth. So-called "flash" laser radar systems wherein a single high energy laser pulse is used to image a target require the extra sensitivity afforded by avalanche photodiodes due to the low return photon count from distant targets.
Low-cost 3D vision for autonomous vehicles
Computational Vision is poised to transition from the laboratory to the battlefield; however, which techniques are the most appropriate for tactical applications? This report provides a review of 3D vision techniques and evaluates their potential application to various classes of autonomous vehicles from a systems engineering perspective. This report provides an overview of 3D vision techniques, evaluates robustness and susceptibility to countermeasures, evaluates vehicle integration requirements, and identifies promising approaches.
High-gain 0.8-um CMOS readout integrated circuit for FM/CW line-imaging ladar
We are engaged in research of readout techniques and development of readout integrated circuits for active and active/passive imaging systems under development at the Army Research Laboratory. Here we report a readout integrated circuit chip designed for ARL's FM/cw line-imaging ladar. The readout chip consists of two 1 x 8 element arrays of high-gain amplifiers that convert the input photocurrent signal to a voltage signal appropriate for digitization. Each amplifier consists of a transimpedance input stage op amp followed by a voltage-gain op amp and output buffer. The input transimpedance stage is a CMOS operational amplifier designed for a transimpedance gain of almost 1 MΩ. The voltage amplifier of stage two, also an operational amplifier, is designed to provide additional gain of about 150. Test chips have been fabricated and are being tested. The initial measured transimpedance gain of the entire amplifier cell is 130 MΩ. We discuss the chip design, physical layout, and initial performance test results.
Infrared in Strategic Defense
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MDA IR sensor technology program and applications
Infrared (IR) sensors are needed for ballistic missile defense (BMD). BMD IR sensor applications extend from surveillance using ground, airborne and space-based platforms, to both endo- and exo-atmospheric interceptor seekers. Even though IRFPAs using material systems, such as HgCdTe and InSb, are adequate for most tactical military applications, certain IR systems for BMD have much more stringent requirements. With a cold dim target a long distance away, IR sensors having extended wavelengths are needed in the mid course. The requirements of BMD IR sensors with high sensitivity, large format, small pixel size and high frame rate, plus long cutoff wavelength and operating at low temperatures present great challenges to IR sensor technology. This presentation will cover the current MDA IR sensor technology development, its system application for block upgrades and advanced concepts.
Toward Third-Generation Thermal Imagers I
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Challenges for third-generation cooled imagers
Stuart Horn, Paul Norton, T. Cincotta, et al.
Third-Generation, two-color infrared cooled sensors are being developed in order to allow the Army to detect and identify enemy forces at ranges beyond that at which the enemy can detect them. This will ensure that the Army continues to "own" night operations. Developing the technology needed to field these high-performance third-generation cooled imagers poses many challenges to the infrared community. These devices, which are expected to provide high spatial and temporal resolution simultaneously in two-to-three infrared bands, will dramatically increase the ability to find targets in defilade, and will be a major technological breakthrough. Performance has to be close to the theoretical limit, dominated by the limits of photon noise. Cost is also a major factor if sufficient numbers of such sensors are to be fielded. The benefits of this technology are now described, followed by a summary of the challenges faced in meeting the cost and performance objectives.
Megapixel HgCdTe MWIR focal plane array with a 15-um pitch
Pierre Castelein, Francois Marion, Jean-Luc Martin, et al.
In this paper we present the first demonstration at LETI infrared laboratory of a megapixel HgCdTe MWIR focal plane array with a 15μm pitch. The detectors were interconnected by indium bumps to the CMOS readout circuit. The design of these interconnections has been adapted from the standard CEA-LETI process to achieve resolution and uniformity required by the reduced pitch. Because of the mismatch of thermal dilatation coefficients between the substrate and the HgCdTe, specific developments were necessary in order to achieve the hybridization process with an extremely reduced amount of defaults. The readout circuit was designed in a 3.3V/0.35μm CMOS technology. Its main features were to allow the validation of the hybridization and technological processes. A Megapixel IRCMOS has been fully characterized at 77K exhibiting excellent electro-optical performances and an operability greater than 99.8%.
State of the art in large-format IR FPA development at CMC Electronics, Cincinnati
Mark E. Greiner, Mike Davis, John W. Devitt, et al.
Last year, CMC reported performance data on the first article large format Indium Antimonide (InSb) Focal Plane Arrays (FPAs) produced at CMC Electronics Cincinnati (CMCEC). CMCEC's FPA design contains novel, thermally matched elements, which allow scaling from 256 x 256 pixel FPAs up to and including 1Kx1K and 2Kx2K FPAs as shown in Figure 1. Since a common process and wafer size is used to fabricate 256 x 256 640 x 512, 1Kx1K and 2Kx2K FPAs, the main issue in providing 2Kx2K FPAs is one of yeild improvement, not invention. Approximately 30 of these large format 1Kx1K and 2Kx2K FPAs have been built and 18 have been integrated into deliverable systems over the last year.
Status of third-generation focal plane array IR detection modules at AIM
Wolfgang A. Cabanski, Rainer Breiter, Karl-Heinz Mauk, et al.
The 3rd generation of infrared (IR) detection modules is expected to provide video resolution or even more pixels and advanced functionality's like multicolor or multi band capability, higher frame rates and better thermal resolution. This paper is intended to present the present status at AIM on such technologies. High speed MCT MWIR devices with 3.4-5μm spectral band and 256x256 pixels in a 40μm pitch are designed to provide > 800Hz full frame rate with pixel rates as high as 80Mpixels/s. In case of the dual color device, the MWIR is split into a 3.4-4.2μm and 4.2-5.1μm section. The device is done with 192x192 pixels in a 56μm pitch. The read out circuit is designed to read while scan in a flash integration mode to allow nearly full frame integration for low NETD at high frame rate. A miniaturized command and control electronics with 14 Bit deep digital serial output provides state of the art interfaces. Pro's and cons of spectral selective detection with either temporal coincidence of the different colors or in a sequential mode with smaller pitch, better fill factor and the ability to use the wide band image for visualization and specific image processing algorithms are discussed. In any case, the high frame rate of the 2 devices puts a new standard for seeker head or missile approach warning (MAW) applications. The 3.4-5μm devices exhibit excellent thermal resolution with NETD<10mK @F/2, 1ms. In case of the dual color devices results on electrooptical performance are discussed together with details of the spectral cross talk encountered for 2 colors and its impact on maw performance. A dual band detector combining MWIR and LWIR detection in each pixel is presently under development. This device is done in quantum well (QWIP) technology. The design goal and features of this new device are discussed together with typical applications.
Large-format and multispectral QWIP infrared focal plane arrays
Arnold C. Goldberg, Kwong-Kit Choi, Murzy Jhabvala, et al.
The next generation of infrared (IR) focal plane arrays (FPAs) will need to be a significant improvement in capability over those used in present-day second generation FLIRs. The Army's Future Combat System requires that the range for target identification be greater than the range of detection for an opposing sensor. To accomplish this mission, the number of pixels on the target must be considerably larger than that possible with 2nd generation FLIR. Therefore, the 3rd generation FLIR will need to be a large format staring FPA with more than 1000 pixels on each side. In addition, a multi-spectral capability will be required to allow operability in challenging ambient environments, discriminate targets from decoys, and to take advantage of the smaller diffraction blur in the MWIR for enhanced image resolution. We report on laboratory measurements of a large format (1024 x 1024 pixels) single-color LWIR IR FPA made using the corrugated quantum well infrared photodetector (QWIP) structure by the ARL/NASA team. The pixel pitch is 18 μm and the spectral response peaks at 8.8 μm with a 9.2 μm cutoff. We report on recent results using a MWIR/LWIR QWIP FPA to image the boost phase of a launch vehicle for missile defense applications and a LWIR/LWIR FPA designed specifically for detecting the disturbed soil associated with buried land mines. Finally, we report on the fabrication of a new read-out integrated circuit (ROIC) specifically designed for multi-spectral operation.
Cooled FPAs and Applications I
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HgCdTe focal plane array cost modeling
Thomas J. Sanders, Glenn T. Hess
Focal plane arrays (FPAs) are used in many applications for detecting infrared (IR) radiation where normal sight with light in the visible spectrum is not possible. To effectively detect this IR radiation, complex semiconductor diodes, cooled to low temperatures, are usually used. The most common of these semiconductor materials is the II-VI alloy semiconductor system using HgCdTe, which is often called MCT. Focal plane arrays with over 1000 pixels have been fabricated. The cost of these very complex systems is becoming a very important consideration in decisions of where to use these FPAs. The focal plane array actually consists of two semiconductor parts with a sophisticated cooling assembly. The semiconductor parts are the MCT detector device itself and a companion device called the read-out circuit. The cost model presented in this paper consists of various expressions as functions of physical parameters that can be measured, calculated from data or estimated. Although accurate absolute cost data may not be available (because it does not exist or is proprietary to a company), cost estimates can be effectively used to determine relative cost between two designs or processes. In addition, when these cost models are coupled with the STADIUM design of experiments simulation methodology, accurate predictions of the most dominant cost drivers can be obtained. This cost model and its algorithms are coupled with a commercial software program called IR-SIM.
Advanced HgCdTe focal plane arrays
Muren Chu, Hrayr K. Gurgenian, Shoghig Mesropian, et al.
Boron implantation and heterojunction epitaxy have been the standard techniques for the production of HgCdTe focal plane arrays for a variety of applications. Each of these techniques has its special advantageous features. In this paper, we will describe an advanced HgCdTe junction formation technique, the planar ion-implantation-isolated heterojunction process, which utilizes the benefits of both the boron implantation and the heterojunction epitaxy techniques. HgCdTe arrays in the format of 320x256 and 640x512 have been produced by this method. The characteristics of these arrays are reported.
Implementation and measurement of gamma radiation on IR photodetectors HgCdTe IRCMOS
Sabine Suffis, Marcel Caes, Michel Tauvy, et al.
For some years, the IR laboratory of ONERA (France) carried out accurate electro-optical characterization on IR detectors. This paper presents some works about IR detector radiation hardness measurements: ONERA, in collaboration with DGA/CEG, measured the effects of gamma radiation on high wavelength IRCMOS. The test conditions respect hard constraints, particularly, during the radiation, detectors were cooled and operating. This paper reviews the implementation of these tests in very hard environment electromagnetic field, radiation, noise ...) and of a test protocol. In spite of severe environmental conditions, quality of measurement is comparable with those done in the laboratory. General component behaviors, transionnal and permanent effects, are summed up for very high dose rate.
Digital cooled InSb detector for IR detection
Ofer Nesher, Shimon Elkind, Amnon Adin, et al.
A Focal Plane Array (FPA) with a digital output for cooled IR detectors has recently attracted a lot of attention due to its advantages over detectors with analog outputs. Of special importance is the potential to have a better long term stability of the Residual Non Uniformity (RNU). Last summer SCD introduced a new high performance digital signal processor for 640x512 InSb infrared detectors, which includes analog to digital conversion performed inside the signal processor itself (at the focal plane). This signal processor has been bonded to InSb detector arrays and tested both electrically and radiometrically within a dewar. Special proximity electronics was developed for the operation of the FPA, including a Field Programmable Gate Array (FPGA) device. The complete device functions as a multi-chip system, enabling high degree of flexibility and easy integration at the system level. The total power dissipation of the FPA is less than 100mW at a frame rate of 100Hz, which is even less than that obtained with comparable/conventional analog FPAs. The NETD of the detector is less than 10.5mK at 50% of the full range 13Me-. The RNU is less than 0.02%STD/DR from 2% up to 90% of the full range. It is important to note that in the case of a digital detector the readout noise the NETD and the RNU of the detector are the total system values. This stand alone Digital Detector Dewar Cooler (D3C) presents a new industrial standard for cooled IR detectors.
AIM image processing electronics for FPA IR detection modules
To provide solutions for thermal imaging modules including image processing functions like non-uniformity correction and video display three platforms of image processing electronics have been developed to match AIM's family of FPA IR detection modules including MCT, PtSi and QWIP detectors. The detection modules include command and control electronics (CCE) with 14 bit digitization of the sensor output. Different detector data interfaces have been realized to cover various application requirements like a 14 bit parallel interface for short distances, a LVDS serial interface for medium distances and a high speed serial link interface for distances up to 30 m. The image processing boards make use of fast digital signal processors (DSP's) to have a flexible architecture for implementation of algorithms like a scene- based non-uniformity correction. The MVIP electronics is a general board to operate with all detection modules like small and large format devices. The HSVIP board was designed to operate the high-speed and dual-color MCT detection modules with fast data rates up to 80 Mpixels/s while the HPVIP is a low power board to operate only small format detectors. The paper will give an overview of AIM's image processing electronics and their functionality together with the IR detection modules for specific applications.
Cooled FPAs and Applications II
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HgCdTe HDVIP detectors and FPAs for strategic applications
Arvind I. D'Souza, Maryn G. Stapelbroek, E. R. Bryan, et al.
Detector characteristics of Cu- and Au-doped High Density Vertically Integrated Photodiode (HDVIP) detectors as well as Cu-doped HDVIP Focal Plane Arrays (FPAs) are presented in this paper. Individual photodiodes in test bars were examined by measuring I-V curves and the associated resistance-area (RA) product as a function of temperature. The Au-doped MWIR [λc(78 K) = 5 μm] HDVIP detectors RoA performance was within a factor of two or three of theoretical. Noise as a function of frequency has been measured on Au-doped MWIR HgCdTe HDVIP diodes at several temperatures under dark and illuminated conditions. Low-frequency noise performance of the Au-doped MWIR diode in the various environments is characterized by the ratio α of the noise current spectral density at 1 Hz to the value of the diode current. For photocurrent at 140 K, αPHOTO = 1.8 x 10-5. The value of αPHOTO is the same at both zero bias and 100 mV reverse bias. At 160 K, αPHOTO is slightly lower but still in the low 10-5 range. Excess low-frequency noise measured at 140 K and 100 mV reverse bias in the dark has αDARK = 1.4 x 10-5. At 160 K and 100 mV reverse bias, αDARK is in the mid 10-5 range. At 140 K,the dark current at 8.2 V reverse bias was equal to the photocurrent at 100 mV reverse bias and close to the photocurrent at zero bias. αDARK = 1.85 x 10-3 at -8.2 V. This ratio is two orders of magnitude greater than αPHOTO. At 8.2 V reverse bias, the current was amplified by avalanche processes. Similar results were obtained on the Au-doped diode at 160 K. Diffusion current dominates dark current at 100 mV reverse bias at T = 185 K and T = 220 K. The ratio, αDARK approximately αPHOTO in the low to mid 10-5 range, i.e. dark diffusion current generates excess low frequency noise in the same manner as photocurrent. In addition, 256 x 256 Cu-doped detector arrays were fabricated. Initial measurements had seven out of ten FPAs having operabilities greater than 99.45% with the best 256 x 256 array having only two inoperable pixels.
Composite substrate for large-format HgCdTe IRFPA
Nibir K. Dhar, Y. P. Chen, Gregory N. Brill, et al.
Research on silicon based composite substrates is being conducted at the Army Research Laboratory. These substrates can be used to deposit HgCdTe alloys to fabricate large-format infrared photodetector arrays. Traditionally, composite structures are fabricated by growing CdZnTe buffer layers on Si substrates using molecular beam epitaxy process. Recently, we have demonstrated that composite structures using CdSeTe can also be used. The CdSeTe compound offers better surface morphology and control of composition. In this work we present our results on the Si-based substrate technology and its application in the use of substrate material for LWIR HgCdTe detector development. In this paper we also present our study of molecular beam epitaxy and characteristics of CdSexTe1-x ternary films on Si. A detailed study of the alloy composition and lattice structures were investigated. In general, we find that the crystalline quality of CdSeTe films on Si is superior to CdZnTe on Si. Best CdSeTe/Si samples had EPD as low as 1.4x105 cm-2. This study also discusses a comparison of cation versus anion mixing in chalcogenide compounds. Results of LWIR detectors on CdTe/Si are also presented as a precursor and rational for a need of better lattice-matched substrates other than the conventional CdZnTe/Si substrates.
Silicon for visible-to-VLWIR photon detection
Photon detectors and focal plane arrays (FPAs) are fabricated from silicon in many varieties. With appropriate choices for detector architecture, dopants, and operating temperature, silicon can cover the spectral range from ultraviolet to the very-long-wavelength infrared (VLWIR), exhibit high internal gain to allow photon counting over this broad spectral range, and can be made in large array formats for imaging. DRS makes silicon detectors and FPAs with unique architectures for a variety of applications. Large-format, VLWIR FPAs based on doped-silicon Blocked-Impurity-Band (BIB) detectors have been developed. These FPAs comprise an array of BIB detectors interfaced via indium column interconnects to a matching read-out integrated circuit (ROIC). Arsenic-doped silicon (Si:As) BIB detector arrays with useful photon response out to about 28 μm are the most fully developed embodiment of this technology. FPAs with Si:As BIB arrays have been made in a variety of pixel formats (to 10242) and have been optimized for low, moderate, and high infrared backgrounds. Antimony-doped silicon (Si:Sb) BIB arrays having response to wavelengths 40 μm have also been demonstrated. Avalanche processes in Si:As at low temperatures (~ 8 K) have led to two unique solid-state photon-counting detectors adapted to infrared and visible wavelengths. The infrared device is the solid-state photomultiplier (SSPM). To our knowledge, it is the only detector capable of counting VLWIR photons (formula available in paper) with high quantum efficiency. A related device optimized for the visible spectral region is the visible-light photon counter (VLPC). The VLPC is a nearly ideal device for detection of small bunches of photons with excellent time resolution. VLPCs coupled to scintillating fibers have demonstrated new capabilities for energetic charged particle tracking in high-energy physics. A fiber tracking system that utilizes VLPCs is currently in operation in the D0 detector at Fermilab's Tevatron. VLPCs may also be useful for quantum cryptography and quantum computation. Finally, DRS makes imaging arrays of pin-diodes utilizing the intrinsic silicon photoresponse to provide high performance over the 0.4 - 1.0 μm spectral range operating near room temperature. pin-diode arrays are particularly attractive as an alternative to charge-coupled devices (CCDs) for space applications where radiation hardening is needed.
Key performance drivers for cooled large IR staring arrays
As far as high performance IR detectors are concerned, cooled 2D arrays are more and more used in both IR medium and long wavebands for many different applications. Although it is easy to get an image with 2D staring arrays in comparison with TDI linear arrays, it is more difficult to answer the full system needs in terms of high performances in very tough environmental conditions. As a matter of fact, performances of large cooled staring arrays are mainly limited by the ability of the system to correct the non-uniformities of the arrays and this ability depends on some keys parameters like linearity, uniformity, and stability of operating temperature. These parameters have to remain constant in function of the change of environmental conditions. In this paper, the main key parameters for staring arrays are reviewed and performances of large new SOFRADIR cooled staring arrays are discussed in MW. Finally third generation key drivers are discussed.
4-µm cut-off MOVPE Hg1-xCdxTe hybrid arrays with near-BLIP performance at 180K
Recent advances in MOVPE growth and heterostructure fabrication technology mean that infrared detector arrays based on Hg1-xCdxTe now have the potential to produce high performance imagery when operated in the temperature range 150-200 K. This has a number of system advantages including reduced cooler power consumption and increased cooler life. This paper reports the fabrication and assessment of a MW staring array with a cut-off of 4 μm at 150 K for intermediate temperature operation. Near background limited (BLIP) performance was achieved at temperatures up to 180 K with a median NETD better than 12 mK. Above this temperature, the array still operates normally however there is an exponential increase in the number of noisy pixels, and the median NETD degrades more rapidly than predicted from Shot noise. This behavior is consistent with increased low frequency or 1/f noise at the higher temperatures. This excess noise is not a fundamental limitation and if it could be eliminated, the array would remain close to BLIP up to 200 K.
Type-II superlattice photodiodes: an alternative for VLWIR detection
In the very long wavelength infrared (VLWIR) band, λ>14 microns, the detector materials are currently limited to extrinsic semiconductors. These extrinsic materials can be either heavily doped bulk semiconductor, like silicon or germanium, or a doped quantum well heterostructure. An alternative choice that provides the opportunity for higher temperature operation for VLWIR sensing is an intrinsic material based on a type-II InAs/Ga(In)Sb superlattice. There are many possible designs for these superlattices which will produce the same narrow band gap by adjusting individual layer thicknesses, indium content or substrate orientation. The infrared properties of various compositions and designs of these type-II superlattices have been studied. In the past few years, excellent results have been obtained on photoconductive and photodiode samples designed for infrared detection beyond 15 microns. An overview of the status of this material system will be presented. In addition, the latest experimental results for superlattice photodiodes with cut-off wavelengths as long as 30 microns will be covered.
Adaptive denoising at infrared wireless receivers
Xavier N. Fernando, Srithar Krishnan, Hongbo Sun, et al.
This paper proposes an innovative approach for noise cancellation at infrared (IR) wireless receivers. Ambient noise due to artificial lighting and the sun has been a major concern in infrared systems. The background induced shot noise typically has a power from 20 to 40 dB more than the signal induced shot noise and varies with time. Due to these changing conditions, infrared wireless receivers experience high level of non-stationary noise. The objective of the work mentioned in this paper is to develop digital signal processing algorithms at the infrared wireless system to combat high power non-stationary noise. The noisy signal is decomposed using a joint time and frequency representation such as wavelets and wavelet packets, into transform domain coefficients and the lower order coefficients are removed by applying a threshold. Denoised version is obtained by reconstructing the signal with the remaining coefficients. In this paper, we evaluate different wavelet methods for denoising at an infrared wireless receiver. Simulation results indicate that if the noise is uncorrelated with the signal and the channel model is unavailable the wavelet denoising method with different wavelet analyzing functions improves the signal to noise ratio (SNR) from 4 dB to 7.8 dB.
Signal Processing In and Behind the FPA
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Design of a 12-megapixel imager with a nanowatt A/D converter at each pixel
The design for a large format digital visible light area array was developed based on A/D conversion at each pixel. Production CMOS technology was used in the development of a monolithic front side illuminated photo diode pixel. Each pixel includes a one loop MOSAD, multiplexed oversample A/D, converter, the photo diode and a buffered output to support a very large array format operating at a high frame rate. MOSAD is a modification of the delta sigma approach to A/D conversion. The requirements are to develop a 4,000 x 3,000 pixel array capable of up to 1,000 frames per second sample rate. A design was developed using the AMIS 0.35 μm CMOS process with a single poly and three metal layers. To approximately fit a 35 millimeter optics format, a pixel size of 8.5 μm was selected. There are no operational amplifiers required at the pixel to perform the A/D function, thus allowing a high fill factor. With this pixel size, a 48% fill factor and 38% photo diode area was achieved. The design can produce a pixel size of 4.3 μm square with the use of 0.18 μm CMOS without sacrificing fill factor. Alternate approaches to satisfy the 1 kiloframe sample rate with up to 10 bits dynamic range were analyzed. The design is still in progress with layout and simulation of the critical elements complete. This development program is sponsored by the Army White Sands Missile Range.
Real-time processing and hard disk storage of high-bandwidth IR FPA data streams
Juergen Zettner, Christian Peppermueller, Oliver Schreer, et al.
This article presents strategies, implementations and applications of handling infrared FPA data streams at high data rates on most recent standard PCs. Those data streams require maximum data throughput of modern PCs. Real-time non-uniformity correction (gain and offset correction) of those high speed infrared FPA data streams will be discussed. The performance of PC based systems for Real-Time data Acquisition and data Hard Disk Storage (RT-AHDS) will be described in more detail. Some of the Thermosensorik systems for use in research and development, as well as in in-line testing systems in industry for various applications will be presented. This paper describes some of the demanding tasks for the PC based concept, as well as some major advantages.
Pixel fusion and superresolution for Matis handheld thermal imager
Michel Broekaert, Joel Budin
Thermal imagers and infrared seekers have the particularity to possess two optical flows, one coming from the observed landscape, the other coming from parasitic radiation of the camera. To this can add a drift of detectors characteristics in time. These parasitic radiation's and detector's characteristics temporal and spatial drifts may have multiple origins: the optics and camera housing thermal drifts, the focal plane array thermal drift during cooldown, the thermal gradients in the focal plane array during cooldown. In case of a very short Joule Thomson cooldown, we are in the hardiest case where all these drifts appear simultaneously. The detector's characteristics, the dark current, the cut-off wavelength, can be very sensitive to the cooling temperature. We can easily understand that, in such conditions non-uniformities corrections are extremely difficult to perform, unless waiting all parameters became stabilized in temperature and then risk to reduce the operational performances. To avoid these difficulties we now suggest, to approach this problem in a fully different way, by fusing information from the successive frames of a video sequence, and by getting benefit of some properties of optical flows of the scene and the camera. This Pixels fusion of successive frames allows to find the motion and vibrations of the carrier. With this knowledge we can extract several new functionalities. One of these is the image stabilization in the terrestrial coordinate system, or the filtering of the carrier vibrations. Another is to derive the non-uniformities corrections of the IR sensor. With this help, we can also implement the detection and tracking of moving targets in the scene. Finally, the improvement of spatial resolution and concurrently the decrease of the temporal noise are also allowed by superresolution. In this paper, we describe the applied methods and present processed videos sequences. New generations of ASICs, FPGAs et DSPs components can now be used to implement powerful digital image processing taking advantage of pixels fusion, even for handheld thermal imagers.
Scene-based correction of image sensor deficiencies
Petter Torle, Ingmar A. Andersson, Leif Haglund
Methods for scene-based removal of fixed pattern noise from IR image sequences are described and evaluated in this paper. In particular, methods that are based on registration of global motion between individual image frames are discussed. A pre-processing calibration procedure is also presented, which produces an initial set of correction parameters. The algorithms are tested with good results on real image data from a two-dimensional focal plane array detector and a scanning one-dimensional detector.
Toward Third-Generation Thermal Imagers II
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Imaging spectropolarimetry
Spectrometry and polarimetry measurements are important to modern science and engineering in an extremely wide variety of fields such as atomic and chemical processes, materials identification and characterization, astronomy, remote sensing, and stress analysis. The basic principle is that when light is emitted or absorbed by, scattered or reflected from, or transmitted through a physical material, its spectral content and polarization state are often affected. Analysis of the changes imposed by these processes then has the potential to reveal useful information about the sources. Example applications are: (1) stress-induced birefringence (photoelasticity); (2) remote sensing, object discrimination, shape measurement; (3) communications (polarization shift keying, deterimental effects on fiber networks); (4) astronomy (solar magnetic fields); (5) scattering, materials identification (retinal nerve fiber layer thickness measurement); (6) ellipsometry (materials characterization, complex index of refraction, layer thicknesses); (7) atomic physics; (8) displays (color LCDs merge colorimetry and polarization).
Microscale waveplates for polarimetric infrared imaging
Cornell S. L. Chun
Imaging sensors to detect the four Stokes parameters, which have high sensitivity and high frame rates and are light weight and portable, have not been developed. In this paper, we report on our development of novel microscale achromatic retarders. A two-dimensional array of these retarders can be combined with an array of linear polarizers in an imaging sensor. This sensor will be able to capture images of the four Stokes parameters over a wide wavelength band. The achromatic retarder is a combination of two single-order waveplates. Each single-order waveplate is a surface-relief grating which was modeled using Rigorous Coupled Wave Theory. The images of an idealized terrestrial scene were generated by polarimetric ray tracing. We then simulate the image of circular polarization which would appear at the output of a realistic sensor. We conclude that the wide-band sensor is able to image Stokes parameter V when the degree of circular polarization in the scene is approximately 2% or greater.
Multisensor image fusion and mining in a COTS exploitation environment
David A. Fay, Richard T. Ivey, Neil Bomberger, et al.
We have continued development of a system for multisensor image fusion and interactive mining based on neural models of color vision processing, learning and pattern recognition. We pioneered this work while at MIT Lincoln Laboratory, initially for color fused night vision (low-light visible and uncooled thermal imagery) and later extended it to multispectral IR and 3D ladar. We also developed a proof-of-concept system for EO, IR, SAR fusion and mining. Over the last year we have generalized this approach and developed a user-friendly system integrated into a COTS exploitation environment known as ERDAS Imagine. In this paper, we will summarize the approach and the neural networks used, and demonstrate fusion and interactive mining (i.e., target learning and search) of low-light visible/SWIR/MWIR/LWIR night imagery, and IKONOS multispectral and high-resolution panchromatic imagery. In addition, we will demonstrate how target learning and search can be enabled over extended operating conditions by allowing training over multiple scenes. This will be illustrated for the detection of small boats in coastal waters using fused visible/MWIR/LWIR imagery.
Bio-inspired optics
Dean A. Scribner, Leonard J. Buckley, Michael P. Satyshur, et al.
Combining bio-inspired optical designs with new materials -- that have a capability to dynamically change index of refraction - may provide new capabilities and increased system performance. This paper discusses recent interest in mimicking some of the adaptive features of biological imaging systems, identifies new optical materials being developed, and discusses some simple applications such as zoom lenses with no moving parts and foveated imaging systems. Mention is also given to the future challenges of developing materials with dynamic refractive indexes and gradients.
Operation and performance of a color image sensor with layered photodiodes
A silicon image sensor has been developed and placed in production using standard 0.18 μm CMOS process having three stacked photodiodes per pixel location to provide full-color imaging without external color filters. With a fill factor exceeding 50%, this image sensor achieves approximately 45% peak quantum efficiency in the mid range visible and provides usable response extending from the near-ultraviolet to the near-infrared. Initial results from a commercial digital still camera indicate that this device can produce excellent color reproduction with equivalent ISO film speeds from 100 to 400 and that it produces images free from color artifacts common in images made with sensors incorporating color filter arrays. Development is now underway on camera equipment designed to operate this image sensor in a variety of scan modes.
SWIR FPAs and Their Applications
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Characterization and analysis of InGaAsSb detectors
M. Nurul Abedin, Tamer F. Refaat, Ravindra P. Joshi, et al.
Profiling of atmospheric CO2 at 2 μm wavelength using the LIDAR technique, has recently gained interest. Although several detectors might be suitable for this application, an ideal device would have high gain, low noise and narrow spectral response peaking around the wavelength of interest. This increases the detector signal-to-noise ratio and minimizes the background signal, thereby increasing the device sensitivity and dynamic range. Detectors meeting the above idealized criteria are commercially unavailable for this particular wavelength. In this paper, the characterization and analysis of Sb-based detectors for 2 μm lidar applications are presented. The detectors were manufactured by AstroPower, Inc., with an InGaAsSb absorbing layer and AlGaAsSb passivating layer. The characterization experiments included spectral response, current versus voltage and noise measurements. The effect of the detectors bias voltage and temperature on its performance, have been investigated as well. The detectors peak responsivity is located at the 2 μm wavelength. Comparing three detector samples, an optimization of the spectral response around the 2 μm wavelength, through a narrower spectral period was observed. Increasing the detector bias voltage enhances the device gain at the narrow spectral range, while cooling the device reduces the cut-off wavelength and lowers its noise. Noise-equivalent-power analysis results in a value as low as 4x10-12 W/Hz1/2 corresponding to D* of 1x1010 cmHz1/2/W, at -1 V and 20°C. Discussions also include device operational physics and optimization guidelines, taking into account peculiarity of the Type II heterointerface and transport mechanisms under these conditions.
High-resolution extended NIR camera
Scott A. Cabelli, Jianmei Pan, Steven G. Bernd, et al.
A High Resolution Near-Infrared (NIR) Camera has been developed and tested. This NIR camera uses a HgCdTe detector array which allows for imaging at high operating temperatures. The camera's format is 640x512 pixels with an 18 μm pitch. We have obtained high broadband spectral response from 0.9 to 2.0 micron with near 100% optical fill factor. The camera is designed as a turnkey system that uses the industry standard Camera Link digital interface. The electronics are located remotely from the sensor head allowing it to be adapted to existing optical systems. This compact camera has been targeted for military, scientific and telecommunication applications. This paper will detail the measured camera performance.
Miniaturized 320x256 indium gallium arsenide SWIR camera for robotic and unmanned aerial vehicle applications
We describe a new InGaAs SWIR microcamera developed for robotic and UAV applications. The camera has a volume less than 27 cm3, weighs less than 100 g, and consumes less than 1.4 W. The camera operates with the focal plane array at room temperature and is sensitive to the 0.9 μm to 1.7 μm SWIR band with a detectivity, D*, greater than (formula available in paper). The InGaAs focal plane array has 320x256 pixels on a 25 μm pitch. It features snapshot-mode integration with a minimum exposure time of 500 ns making it ideally suited for all-solid-state range-gated imaging. The full-frame readout rate is greater than 400 frames per second. The built-in windowing feature is highly flexible with as many as 8 arbitrarily shaped regions-of-interest can be located anywhere (including overlapping) on the imager. Eight 64 x 64 regions of interest (ROIs), for example, can be read out faster than 1000 frames per second with a single 64 x 64 ROI read out faster than 5000 frames per second enabling high speed target acquisition and tracking applications.
Application needs and trade-offs for short-wave infrared detectors
Philippe Chorier, Philippe M. Tribolet, Patrice Fillon, et al.
Short Wave Infrared (SWIR) band is an interesting waveband for a lot of industrial applications like process control, spectrometry, telecommunications and space as well as for military applications like eye-safe laser imaging. The detectors available in this waveband are based on silicon with a 1.1 μm cut-off wavelength and on InGaAs with 1.6_2 μm cut-off but also on HgCdTe material (MCT), which is a good candidate to answer systems needs with relatively high cut-off wavelength, typically up to 2 or 2.5 μm. All these detectors are T.E. cooled or uncooled allowing cost-effective design approaches. To answer commercial application needs, a lot of trade-offs can be made at level of the SWIR detectors in order to optimize the performances and the associated packaging with the goal to offer cost-effective detectors. As far as military applications are concerned, specific developments are needed in order to fulfill the requirements of future systems. The different needs and detector options are reviewed and discussed in this paper.
Dual-mode FPA for free space communications
Matthew T. O'Grady, Marshall J. Cohen
A new dual mode focal plane array integrating both staring and high-speed data reception readout circuits is proposed. This FPA incorporates an indium gallium arsenide PIN photodiode array optimized for high-speed response and a custom CMOS readout integrated circuit (ROIC). The ROIC includes an integrator and a high-speed transimpedance amplifier within each pixel for photosignal detection and also peripheral circuits for controlling the readout operation. These circuits enable the entire pixel array or a smaller, randomly addressable pixel window within the array to be read out in stare mode and also for a single pixel to be selected and read out in high-speed data reception mode. The stare mode features snapshot integration, very high frame rates and continuously adjustable sensitivity over a wide range, and the data reception mode is capable of detecting a high-speed data stream from anywhere within the FPA's field-of-view without the need for mechanical adjustment. The integration of these features into a single FPA enables the development of optical communications networks that can automatically configure themselves without prior knowledge of each transceiver’s location. This paper introduces the architecture, design and functionality of the device. It also outlines some of the design constraints imposed by the dual-purpose functionality.
Uncooled FPAs and Their Applications I
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Selection of the thermal imaging approach for the XM29 combat rifle fire control system
Eric Brindley, Jack Lillie, Peter Plocki, et al.
The paper briefly describes the XM29 (formerly OICW) weapon, its fire control system and the requirements for thermal imaging. System level constraints on the in-hand weight dictate the need for a high degree of integration with other elements of the system such as the laser rangefinder, direct view optics and daylight video, all operating at different wavelengths. The available Focal Plane Array technology choices are outlined and the evaluation process is described, including characterization at the US Army Night Vision and Electronic Sensors Directorate (NVESD) and recent field-testing at Quantico USMC base, Virginia. This paper addresses the trade study, technology assessment and test-bed effort. The relationship between field and lab testing performance is compared and path forward recommended.
320x240 uncooled microbolometer 2D array for radiometric and process control applications
Jean-Luc Tissot, Jean-Pierre Chatard, Sebastien Tinnes, et al.
Uncooled infrared focal plane arrays are being developed for a wide range of thermal imaging applications. Developments are focused on the improvement of their sensitivity enabling the possibility to manufacture high performance radiometric devices with internal temperature stabilized shield to determine the input infrared flux. We present the characterization of a new radiometric device obtained from 320 x 240 uncooled microbolometer array with f/1.4 aperture. This device is well adapted to radiometric or process control applications and moreover shows a high level of stability due to the internal temperature stabilized shield which prevents the detector from camera internal temperature shift artifacts.
Resolution and sensitivity improvements for VOx microbolometer FPAs
Daniel F. Murphy, Adam Kennedy, Michael Ray, et al.
Raytheon Vision Systems (RVS) has achieved a significant technical breakthrough in uncooled FPAs by reducing the pixel size by a factor of two while maintaining state-of-the-art sensitivity. Raytheon is producing high-quality 320 x 240 microbolometer FPAs with 25 μm pitch pixels. The 320 x 240 FPAs have a sensitivity that is comparable to microbolometer FPAs with 50 μm pixels. The array average NETD value for these FPAs is about 30 mK with an f/1 aperture and operating at 30 Hz frame rates. Pixel operability is greater than 99% on most FPAs, and uncorrected responsivity nonuniformity is less than 4% (sigma/mean). These 25 μm microbolometer detectors also have a relatively fast thermal time constant of approximately 10 msec. This state-of-the-art performance has been achieved as a result of an advanced micro machining fabrication process, which allows maximization of both the thermal isolation and the optical fill-factor. These arrays have produced excellent image quality, and are currently fielded in demonstration systems. The reduction in pixel size offers several potential benefits for IR systems. For a given system resolution (IFOV) requirement, the 25 μm pxiels allow a factor of two reduction in both the focal length and aperture size of the sensor optics. These FPAs are applicable to wide-field-of-view, long-range surveillance and targeting missions. The pixel size reduction facilitates a significant FPA cost reduction since the number of die printed on a wafer can be increased, and also has enabled the development of a large-format 640 x 480 FPA array. Raytheon is producing these arrays with very good sensitivity. These arrays have excellent operability and image quality. Several dual FOV prototype systems have been delivered under the LCMS and UAV programs, and are under evaluation at NVESD. Raytheon Vision Systems (RVS) has developed a flexible uncooled front end (UFE) electronics that will serve as the basis for camera engine systems using 320 x 240 and 640 x 480 FPAs. The focus has been to develop architecture suitable for a wide variety of systems from low cost modest performance to high performance military applications. This product has been designed with military environmental and shock and vibration conditions in mind. Intended for small pxiel, high performance applications, the UFE is the ideal cornerstone for ground and airborne UAV, multi-mode sneosr, weapon sight or seeker architectures.
Performance of 320x240 uncooled bolometer-type infrared focal plane arrays
Yutaka Tanaka, Akio Tanaka, Kiyoshi Iida, et al.
The performance of a 320 x 240 bolometer-type uncooled infrared (IR) Focal Plane Array (FPA) is described. Vanadium oxide thin film is adopted for the bolometer material, having a sheet resistance of approximately 10 kohms/square. It is patterned such that the bolometer resistance is by a factor of 10 larger than the sheet resistance. On-chip readout integrated circuit (ROIC) is designed to reduce signal drift, extend dynamic range for object temperature and extend ambient temperature range in which operates non-uniformity correction is carried out with about 1/10 fewer frequency than the former ROIC.The 320 x 240 FPA consists of pixels sensitive to IR radiation and optical black (OB) pixels covered with plate which shuts out IR radiation. Drift is reduced by current mirror circuit, using the OB pixels and digital compensation circuit based on voltage change of OB pixels resulting from change in operation temperature. Both the dynamic range and the ambient temperature range are extended by decreasing integration gain and developing low-noise, low-power and large swing operational amplifier(OP-AMP). Since decrease in integration gain degrades noise equivalent temperature difference (NETD), bias voltage for bolometer is increased by factor of 2 and bandwidth is reduced by route half. Finally, IR image was obtained with prototype camera and NETD value was found to be smaller than 0.1K for F/1 optics at 60Hz frame rate and thermal time constant was measured to be 12 msec.
Low-cost uncooled infrared detector arrays in standard CMOS
This paper reports the development of a low-cost 128 x 128 uncooled infrared focal plane array (FPA) based on suspended and thermally isolated CMOS p+-active/n-well diodes. The FPA is fabricated using a standard 0.35 μm CMOS process followed by simple post-CMOS bulk micromachining that does not require any critical lithography or complicated deposition steps; and therefore, the cost of the uncooled FPA is almost equal to the cost of the CMOS chip. The post-CMOS fabrication steps include an RIE etching to reach the bulk silicon and an anisotropic silicon etching to obtain thermally isolated pixels. During the RIE etching, CMOS metal layers are used as masking layers, and therefore, narrow openings such as 2 μm can be defined between the support arms. This approach allows achieving small pixel size of 40 μm x 40 μm with a fill factor of 44%. The FPA is scanned at 30 fps by monolithically integrated multi-channel parallel readout circuitry which is composed of low-noise differential transconductance amplifiers, switched capacitor (SC) integrators, sample-and-hold circuits, and various other circuit blocks for reducing the effects of variations in detector voltage and operating temperature. The fabricated detector has a temperature coefficient of -2 mV/K, a thermal conductance value of 1.8 x 10-7 W/K, and a thermal time constant value of 36 msec, providing a measured DC responsivity (R) of 4970 V/W under continuous bias. Measured detector noise is 0.69 μV in 8 kHz bandwidth at 30 fps scanning rate, resulting a measured detectivity (D*) of 9.7 x 108 cm√HzW. Contribution of the 1/f noise component is found to be negligible due to the single crystal nature of the silicon n-well and its low value at low bias levels. The noise of the readout circuit is measured as 0.76 μV, resulting in an expected NETD value of 1 K when scanned at 30 fps using f=1 optics. This NETD value can be decreased below 350 mK by decreasing the electrical bandwidth with the help of increased number of parallel readout channels and by optimizing the post-CMOS etching steps. The uniformity of the array is very good due to the mature CMOS fabrication technology. The measured uncorrected differential voltage non-uniformity for the 128 x 128 array pixels after the CMOS fabrication is 0.2% with a standard deviation of only 1.5 mV, which is low due to the improved array structure that can compensate for the voltage drops along the routing resistances in the array. Non-uniformity of temperature sensitivity of the array pixels is measured to be less than 3% with a mean and standard deviation of -2.05 mV/K and 61 μV/K, respectively. The temperature sensitivity of the differential pixel voltages has a measured mean value of 2.3 μV/K, relaxing the requirements on the temperature stabilization. Considering its performance and its simple fabrication steps, the proposed method is very cost-effective to fabricate large format focal plane arrays for low-cost infrared imaging applications.
Portable thermographic camera development incorporating an AC-coupled ferroelectric focal plane array
Arthur Stout, Robert Kienlen
Electrophysics has developed a portable thermographic camera designed for inspection of industrial infrastructure systems such as electrical distribution, mechanical systems and building integrity. The camera incorporates a Raytheon Commercial Infrared BST focal plane array, an AC-coupled ferroelectric infrared sensor with 320 x 240 element resolution. The system is calibrated to measure apparent black body temperatures between 0°C and 500°C with ± 2% RFS accuracy. The camera marketed under the product name Radiometric 500D is a highly modified PalmIR250D featuring a 16-bit real-time parallel interface to an HP iPAQ model 3955 PDA, which features a transreflective 12-bit color display, Compact Flash image storage media, a touch screen interface and voice file recording. Modifications to the chopper eliminate the halo image artifact commonly associated with AC coupled detectors, while the addition of a filter wheel provides expanded dynamic range necessary for high temperature measurements.
Small two-dimensional and linear arrays of polycrystalline SiGe microbolometers at IMEC-XenICs
Vladimir N. Leonov, Ybe Creten, Piet De Moor, et al.
The state-of-the-art characteristics of polycrystalline SiGe microbolometer arrays are reported. An NETD of 100 mK at a time constant of 25 ms is achievable on 14×14 and 200×1 arrays at the system level. It is the result of joint studies targeted at 1/f noise decrease, as well as TCR and uniformity improvements together with the design optimization. Thanks to successful decrease of 1/f noise of SiGe, the arrays were moved from "1/f-noise limited" to "system limited," i.e. to the case of VOx arrays. The mechanical design of pixels was improved affording very precise tuning of the infrared quarter-wave resonant cavity. The resistance and TCR non-uniformity with σ/μ better than 0.2% combined with about 1% noise nonuniformity and 100% pixel operability are demonstrated. The first lots of arrays with 99.98% production pixel yield have already been characterized and the results are being reported.
The universal toolbox thermal imager
Steve Hollock, Graham Jones, Paul Usowicz
The Introduction of Microsoft Pocket PC 2000/2002 has seen a standardisation of the operating systems used by the majority of PDA manufacturers. This, coupled with the recent price reductions associated with these devices, has led to a rapid increase in the sales of such units; their use is now common in industrial, commercial and domestic applications throughout the world. This paper describes the results of a programme to develop a thermal imager that will interface directly to all of these units so as to take advantage of the existing and future installed base of such devices. The imager currently interfaces with virtually any Pocket PC which provides the necessary processing, display and storage capability; as an alternative, the output of the unit can be visualised and processed in real time using a PC or laptop computer. In future, the open architecture employed by this imager will allow it to support all mobile computing devices, including phones and PDAs. The imager has been designed for one-handed or two-handed operation so that it may be pointed at awkward angles or used in confined spaces; this flexibility of use coupled with the extensive feature range and exceedingly low-cost of the imager, is extending the marketplace for thermal imaging from military and professional, through industrial to the commercial and domestic marketplaces.
Uncooled FPAs and Their Applications II
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Uncooled focal plane array detector development at InfraredVision Technology Corp.
Kenneth A. Hay, Dale Van Deusen, Tina Y. Liu, et al.
InfraredVision Technology Corporation (“ITC”) has developed a low-cost Uncooled Focal Plane Array (“UFPA”) for commercial applications. The ITC-1000 series detector module has been targeted for both imaging and radiometric camera applications. The 320x240 VOx microbolometer-based sensor exploits a 37.5-μm pixel structure to provide potential cost reduction for the camera manufacturers. The CMOS Readout Integrated Circuit (“ROIC”) design offers on-chip nonuniformity correction capability and gain control. As an additional feature, the design allows non-temperature stabilized operation. The integration time can be varied for applications where large variations in infrared radiation must be accommodated. Vacuum packaging of the sensors is accomplished using low-cost metal design. A radiometric version of this detector, the ITC-1100, has also been developed for thermographic applications.
Improvements in state-of-the-art uncooled microbolometer system performance based on volume manufacturing experience
Brian S. Backer, Thomas E. Breen, Nancy Hartle, et al.
Starting in the early 1990’s, BAE SYSTEMS began a significant investment in the development of MicroIR Uncooled Microbolometers. 160 x 120, 320 x 240, and 640 x 480 focal plane array (FPA) technology advances in both large pixel and small pixel format have driven Noise Equivalent Temperature Difference (NETD), power, size, weight, and price lower. These improvements have resulted in many new applications that previously could not afford larger, heavier, costlier cooled systems. While advancements in state of the art performance have been published regularly at Aerosense and other industry forums, far less has been discussed on the performance advances that have occurred as a result of volume manufacturing. This paper describes the improvements in performance that have been a result of BAE SYSTEMS leadership position in MicroIR microbolometer manufacturing. With over 15,000 units shipped through 2002, ranging from Standard Imaging Modules (SIM) to Standard Camera Cores (SCC) to complete imaging systems, the cumulative expertise gathered from this manufacturing experience over the past seven years has also pushed the state of the art system performance, in ways that single/small quantity technology demonstrators never could. Comparisons of temporal NETD, spatial NETD, dynamic range, operability, throughput, capacity, and other key metrics from early manufacturing lots to the present will be presented to demonstrate the advances that can only be achieved through volume manufacturing.
Low-cost amorphous-silicon-based 160x120 uncooled microbolometer 2D array for high-volume applications
Uncooled infrared focal plane arrays are being developed for a wide range of thermal imaging applications. Developments are focused on the improvement of their sensitivity enabling the possibility to reduce the pixel pitch in order to decrease the total system by using smaller optics. We present the characterization of a 160 x 120 infrared focal plane array with apixel pitch of 35 μm. The amorphous silicon technology is the latest one developed by CEA/LETI and transferred to ULIS to manufacture 160 x 120 2D arrays. We developed for this device a low cost package based on existing technologies. The readout integrated circuit structure is using an advanced skimming function to enhance the pixel signal exploitation. This device is well adapted to high volume process control applications where spatial resolution is less important than device costs. The electro-optical characterization is presented.
Microbolometer development and production at Indigo Systems
William A. Terre, Robert Cannata, Patrick Franklin, et al.
While microbolometers have been in production for several years, the number of companies producing them is quite small. Indigo Systems has entered into the development and production of VOx based microbolometers, at its Goleta facility. Through the investment of significant capital, Indigo has established a high volume production facility based on the silicon industry model. The 6-inch, cassette-to-cassette, highly automated facility is capable of yielding hundreds of thousands of die per year. Discussed in the paper will be the design and layout of the facility, performance of the devices, as well as yield, trend and throughput data.
Recent advances in TEC-less uncooled FPA sensor operation
Philip E. Howard, John Elwood Clarke, Chuan C. Li, et al.
DRS has previously demonstrated and reported a concept for operating uncooled infrared focal plane arrays (UIRFPA) without the need for UIRFPA temperature regulation. DRS has patented this proprietary technology, which DRS calls TCOMP. TCOMP is a concept that combines an operating algorithm, a sensor architecture and a sensor calibration method, which allow pixel response and offset correction to be performed as a function of the UFPA sensor's operating temperature, thereby eliminating the need for the UIRFPA temperature regulation that would be required otherwise. As a result of the elimination of the temperature regulation requirement, the sensor turn-on time for high performance imaging can be significantly reduced, sensor power is significantly reduced, and the need for stray thermal radiation shields is effectively eliminated. The original TCOMP technique was demonstrated in 1998. Since then DRS has made significant improvements in both the TCOMP algorithm and the calibration process. This paper describes the patented TCOMP concept, presents the results of analysis of the improved TCOMP concept, and provides sensor level data of UIRFPA/sensor performance with the improved TCOMP algorithm.
Uncooled micromachined bolometer arrays on flexible substrates
This paper reports progress on the development of micromachined infrared microsensors on flexible polymer substrates. The flexible substrates were formed by spin-coating polyimide films (HD Microsystems PI-5878G) on silicon wafer carriers. Semiconducting Yttrium Barium Copper Oxide (YBCO) was used as the thermistor. The microbolometer was fabricated using a polyimide (HD Microsystems PI2737) sacrificial mesa and titanium electrode arms. The YBCO thermistor was suspended above the substrate by the electrode arms after the sacrificial layers have been removed by micromachining. The polyimide substrate was then removed from the silicon wafer carrier to complete the fabrication of the infrared microsensors on a flexible polyimide substrate. The measured thermal conductance of the microbolometers ranged from 9.07 x 10-6 W/K for a non-micromachined to 4.0 x 10-7 W/K for a micromachined sensor. As a result, the responsivity and detectivity were measured to be as high as 6.1 x 104V/W and a 1.2 x 108 cmHz1/2/W, respectively, with a 970 nA current bias. This level of performance is comparable to similar miromachined detectors fabricated on silicon substrates.
Advances in uncooled technology at BAE SYSTEMS
Brian S. Backer, Margaret Kohin, Arthur R. Leary, et al.
BAE SYSTEMS has made tremendous progress in uncooled technology and systems in the last year. In this paper we present performance results and imagery from our latest 640x480 and 320x240 small pixel focal plane arrays. Both were produced using submicron lithography and have achieved our lowest NETDs to date. Testing of the 320x240 devices has shown TNETDs of 30mK at F/1. Video imagery from our 640 x 480 uncooled camera installed in a POINTER Unattended Aerial Vehicle is also shown. In addition, we introduce our newest commercial imaging camera core, the SCC500 and show its vastly improved characteristics. Lastly, plans for future advancements are outlined.
Advances in uncooled systems applications
John Steven Anderson, Daryl Bradley, Chungte William Chen, et al.
The Low Cost Microsensors (LCMS) Program recently demonstrated state-of-the-art imagery in a long-range infrared (IR) sensor built upon an uncooled vanadium oxide (VOx) 640 x 480 format focal plane array (FPA) engine. The 640 x 480 sensor is applicable to long-range surveillance and targeting missions. The intent of this DUS&T effort was to further reduce the cost, weight, and power of uncooled IR sensors, and to increase the capability of these sensors, thereby expanding their applicability to military and commercial markets never before addressed by thermal imaging. In addition, the Advanced Uncooled Thermal Imaging Sensors (AUTIS) Program extended this development to light-weight, compact unmanned aerial vehicle (UAV) applications.
Addressing the challenges of thermal imaging for firefighting applications
Joseph Kostrzewa, William H. Meyer, George Poe, et al.
By providing visibility through smoke and absolute darkness, thermal imaging has the potential to radically improve the effectiveness and safety of the modern firefighter. Some of the roles of thermal imaging are assisting in detection of victims; navigating through dark, smoke-filled structures; detecting indications of imminent flash-over/roll-over; identifying and attacking the seat and extension of a fire; and surveying for lingering hot spots after a fire is nearly extinguished. In many respects, thermal imaging is ideally suited for these functions. However, firefighting applications present the infrared community some unique and challenging design constraints, not the least of which is an operating environment that is in some ways more harsh than most aerospace applications. While many previous papers have described the benefits of thermal imaging for firefighters, this paper describes several specific engineering challenges of this application. These include large ambient temperature range, rapidly changing scene dynamics, extreme demands on AGC, and large dynamic range requirements. This paper describes these and other challenges in detail and explains how they were addressed and overcome in the design of Evolution 5000, a state-of-the-art thermal imager designed and manufactured by Mine Safety Appliances (MSA) using Indigo System’s Omega miniature uncooled camera core.
SCC500: next-generation infrared imaging camera core products with highly flexible architecture for unique camera designs
Roy N. Rumbaugh, Kevin Grealish, Tom Kacir, et al.
A new 4th generation MicroIR architecture is introduced as the latest in the highly successful Standard Camera Core (SCC) series by BAE SYSTEMS to offer an infrared imaging engine with greatly reduced size, weight, power, and cost. The advanced SCC500 architecture provides great flexibility in configuration to include multiple resolutions, an industry standard Real Time Operating System (RTOS) for customer specific software application plug-ins, and a highly modular construction for unique physical and interface options. These microbolometer based camera cores offer outstanding and reliable performance over an extended operating temperature range to meet the demanding requirements of real-world environments. A highly integrated lens and shutter is included in the new SCC500 product enabling easy, drop-in camera designs for quick time-to-market product introductions.
Uncooled FPAs and Their Applications I
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High-sensitivity uncooled microcantilever infrared imaging arrays
Scott R. Hunter, Robert A. Amantea, Lawrence A. Goodman, et al.
The structure and operation of a new uncooled thermal infrared imaging detector is described which is composed of bimaterial, thermally sensitive microcantilever structures that are the moving elements of variable plate capacitors. The heat sensing microcantilever structures are integrated with CMOS control and amplification electronics to produce a low cost imager that is compatible with silicon IC foundry processing and materials. The bimorph sensor structure is fabricated using amorphous hydrogenated silicon carbide (a-SiC:H) as the low thermal expansion coefficient material, and gold as the high thermal expansion coefficient bimaterial (14 x 10-6/K). Amorphous hydrogenated silicon carbide is an ideal material in this application due to its very low thermal conductivity (0.34 W/m-K) and low thermal expansion coefficient (4x10-6/K). High resistivity (200-400 Ω/sq) thin Ti/W films are used as the infrared resonant cavity absorber and low thermal loss electrical interconnect to the substrate electrical contacts. A temperature coefficient of capacitance, ΔC/C, (equivalent to TCR for microbolometers) above 20% has been measured for these structures, and modeling of the performance of these devices indicates sensor performance in the range NETD < 5 mK and thermal time constants in the 5 -10 msec range are feasible with this technique. Our development efforts have focused on the fabrication of 320 x 240 imaging arrays with 50 micron pitch pixels. A number of these arrays have been fabricated with performance characteristics that are predicted by a detailed thermo-electro-optical-mechanical model of the sensor. The sensor design and the results from measurements of the thermo-electromechanical and optical properties of the detector arrays will be discussed.
Uncooled MWIR FPAs
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Polycrystalline PbSe x-y addressed uncooled FPAs
M. Carmen Torquemada, Victor Villamayor, M. T. Rodrigo, et al.
A technology for processing low density uncooled focal plane arrays (FPAs) of polycrystalline PbSe has been developed. PbSe is deposited, processed and sensitized on a silicon substrate with two levels of metal separated by a thin dielectric layer of SiO2. An x-y addressed type read out permits a reduced number of leads and high filling factors. Unlike standard polycrystalline PbSe processing method we deposit PbSe by sublimation in vacuum. As-deposited, PbSe is not sensitive to IR light. In order to turn it photosensitive it is necessary to expose the films to specific thermal treatments. We have developed a very efficient sensitization process during which substrates withstand temperatures as high as 450°C. As a technology demonstrator, a low density (8x8 elements) PbSe FPA has been processed. Room temperature detectivities typically yield values of Dλ* (500 K, 300 Hz, 1.2 Hz) approximately 3 x 109 cm Hz1/2/W. The technological capabilities developed can be easily extended to more dense arrays.
Infrared in Air and Space
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Atmospheric sounding at JPL: current and future technologies
JPL is currently managing the instrument operations, calibration and data system for the Atmospheric Infrared Sounder (AIRS) on the EOS Aqua spacecraft. Aqua was launched on May 4, 2002 from Vandenberg Air Force Base. AIRS has 2378 infrared channels with high spectral resolution (1200) covering the 3.7 to 15.4 micron wavelength range. AIRS data are used to produce temperature and humidity profiles useful in predicting weather and monitoring climate. We discuss lessons learned on AIRS in the development and operations as well as plans for next generation systems including SIRAS, a wide field hyperspectral infrared imaging spectrometer which offers AIRS spectral performance at 24x the spatial resolution.
Design and testing of a dual-band enhanced vision system
Scott P. Way, Richard Kerr, Joseph J. Imamura, et al.
An effective enhanced vision system must operate over a broad spectral range in order to offer a pilot an optimized scene that includes runway background as well as airport lighting and aircraft operations. The large dynamic range of intensities of these images is best handled with separate imaging sensors. The EVS 2000 is a patented dual-band Infrared Enhanced Vision System (EVS) utilizing image fusion concepts. It has the ability to provide a single image from uncooled infrared imagers combined with SWIR, NIR or LLLTV sensors. The system is designed to provide commercial and corporate airline pilots with improved situational awareness at night and in degraded weather conditions but can also be used in a variety of applications where the fusion of dual band or multiband imagery is required. A prototype of this system was recently fabricated and flown on the Boeing Advanced Technology Demonstrator 737-900 aircraft. This paper will discuss the current EVS 2000 concept, show results taken from the Boeing Advanced Technology Demonstrator program, and discuss future plans for the fusion system.
Multiple use of an IR missile approach warning system
PIMAWS (Passive IR Missile Approach Warning System) is an Advanced Technology Demonstrator (ATD) for a Passive IR Missile Approach Warning System for use on all flying platforms. The ATD is under development under a contract to the German MoD. First the presentation about PIMAWS will cover the basic design principles to understand, how the system is working (based on real-time signal- and image-processing algorithms): Requirements for passive missile warning. Solution between high repetition rate and sensitivity. PIMAWS design-principles. Status of the Advanced Technology Demonstrator. Image processing algorithms. False alarm reduction. Results of ground based and airborne trials. Video scenes from life firings against the sensor. Integration into Defensive Aids Systems. System Performance. The second part will show, how PIMAWS can be used as a collision avoidance sensor aboard a flying platform: Extended SW function for collision avoidance. Algorithm. Video scenes. The third part will cover the use as a pointable IR staring camera, as an airborne surveillance sensor for SAR and CSAR applications. Video scenes. The end will show different possibilities of the integration into flying platforms.
Helicopter-borne dual-band dual-FPA system
Oliver Schreer, Monica Lopez Saenz, Christian Peppermueller, et al.
Analysis and optimization of camouflage and the development of countermeasures requires careful examination of infrared signatures in the MWIR (3 - 5 μm) and LWIR (8 - 14 μm) atmospheric windows. A dual band infrared camera system based on two FPA detectors (640 x 512 pixels) was developed for simultaneous infrared image acquisition in the MWIR and LWIR spectral range, the Dual-Band FPA640 Aero "Clementine". For the camera system most recent quantum well infrared photo detector (QWIP) and MCT technologies are utilized. The system is designed for a helicopter-borne stabilized platform. It is equipped with two f=100 mm motorized IR lenses with identical fields of view. The image data are transmitted via optical fibers from the camera system to the CompactPCI based computing unit. The computing unit performs non-uniformity correction and digital IR video recording to hard disk drives at full 14 bit dynamic resolution. GPS data are recorded simultaneously. During flight the camera system is operated with a compact remote display and control panel on which the live images are displayed. Sophisticated software permits overlay of MWIR and LWIR images of recorded IR videos with various algorithms. The system is prepared for upgrading with a third FPA detector covering the SWIR atmospheric window in the spectral range 1.3 - 2.5 μm. In the presentation an overview of the system specifications are given. First experiences with helicopter-borne operation are reported.
Development of Si:As impurity band conduction (IBC) detectors for mid-infrared applications
Si:As Impurity Band Conduction (IBC) detectors offer many significant advantages over other conventional photon detectors utilized for the infrared. SiAs offer excellent spectral response out to 28 μm with dark current in the 0.01e/second range at 7K over a wide bias range with no tunneling limitations. In addition, because of the perfect thermal match between the Si:As IBC detector and the readout IC (ROIC), hybrids formed by mating Si:As IBCs and ROICs are mechanically stable and have no hybrid reliability problems. Since Si:As IBC detectore are fabricated on readily available Si substrates, large formats are realizable. Si:As IBC detectors have been under development since the mid 80's at Raytheon Vision Systems (RVS). Under the NSAS SIRTF program, a 256 x 256 Si:As array was developed and successfully integrated into the SIRTF IRAC instrument. This same array is also utilized in the ASTRO-F IRC instrument. Both missions will be launched shortly and provide a significant improvement in our ability to measure the spectral signatures of solar type stars and galaxies at high redshifts under very low background conditions in space. Under the NASA Origins program, in collaboration with NASA Ames Research Center (ARC), RVS developed a high performance 1024 x 1024 Si:As IBC array. This array was tested at Ames Research Center. This paper will review the progress of Si:As IBC development at RVS, present test data from ARC, and discuss the more recent developments in Si:As IBC detectors for the JWST MIRI instrument and future missions such as SPICA, TPF, FIRST and DARWIN.
IR panoramic alerting sensor concepts and applications
Arie N. de Jong, Piet B. W. Schwering
During the last decade, protection of military and civilian operational platforms against weapons like guns, grenades, missiles, Unmanned Combat Aerial (and surface) Vehicles (UCAV's) and mines, has been an issue of increased importance due to the improved kill-probability of these threats. The standard countermeasure package of armour, guns, decoys, jammers, camouflage nets and smokes is inadequate when not accompanied by a suitable sensor package, primarily consisting of an alerting device, triggering consecutive steps in the countermeasure-chain. In this process of alert four different detection techniques are considered: pre-alert, giving the directions of possible attack, detection of an action of attack, identification of the threat and finally the precise localization (3-D). The design of the alerting device is greatly depending on the platform, on which it will be used, the associated and affordable cost and the nature of the threat. A number of sensor packages, considered, developed and evaluated at TNO-FEL is presented for simple, medium size and large and expensive platforms. In recent years the requirements for these sensors have become more and more strigent due to the growing number of scenarios. The attack can practically be from any direction, implying the need for a large Field of Regard (FOR), the attack range can vary considerably and the type of threat can be very diverse, implying great flexibility and dynamic range and rapid response of the sensor. Especially the localization at short ranges is a challenging issue. Various configurations including advantages and drawbacks are discussed.
Image-based navigation for low-flying aerial vehicles
Nikolaus Schweyer, Fred R. Holick, Wilfried Klein
This presentation describes the principle mechanisms how to compute position and attitude of an imaging sensor from a 3D landmark. A mission planning process provides data for the flightpath and appropriate descriptions of landmarks along the flightpath. The processing schemes as well as design considerations for a real time implementation are discussed. The processing consists of three levels. The image processing part extracts edge information from the image of a scene. The pattern recognition part solves the correspondence problem between the edges of the scene and a 3D wire model of the landmark by a relaxation matching operation. Photogrammetric methods finally are used in the pose estimation part. Nonlinear numerical optimization techniques are used to compute position and attitude of the sensor respectively the aerial vehicle.
Fast-cool-down dual gas spray-cooler for pivoted IR detectors
Uwe G. Hingst
Fast cool-down Joule-Thomson cooler for IR-detectors are required for all missiles, which shall be operable within a very short time, like IR-missiles being fired from ground against fast approaching fighter aircrafts at low flight-levels. New IR-seeker developments with larger look-angles require often that the IR-sensor is placed on the pivoted gimbal system. Due to space nd weight limitations the fast cool-down cooler for the sensor often cannot be installed there. The way out is the here presented two-stage "Fast Cool-down Dual Gas Spray Cooler." This by patents protected new fast cool-down cooler for pivoted IR-detectors contains an additionally installed 2nd-stage heat exchange-cooler. It comprises at the rear side of the detector-plate a nozzle through which a highly pressurized and pre-cooled gas (e.g. Argon, Nitrogen) is depressurized and thereby cooled down to its boiling temperature. The resulting liquid/vapor gas-flow behind the nozzle acts then as a spray-cooler for the detector. The 1st-stage apparatus consitutes a Joule-Thomson cooler, driven by a gas with a high cooling efficiency, like Methane (CH4) or Tetrafluoromethane (CF4 ≡ R14) to cool down the gas within the 2nd-stage cooler up to the 1st-stage gas boiling temperature. This cooler concept can be rigidly installed within the IR-seeker in such a way that the gas-orifice from the 2nd-stage cooler is just behind the pivoted IR-sensor plate. This solution requires no direct mechanical connection (gas tube) to the detector-plate. No additional weight impacts nor mechanical forces are provided to the gimbal system and its detector except the small kinetic cooler gas flow forces. With such a "Fast Cool-down Dual Gas Spray Cooler-System" with Argon and CF4 or alternatively CH4 a fast-cool down of the IR-detector to 100K (-173°C) has been achieved within less than 2.3 seconds from an ambient soak temperature of 323 K (+50°C). Compared with single-stage Joule-Thomson coolers this concept provides an unsurpassed cool-down time with a high cooling efficiency even from high soak temperatures. Taking into account that the cooler provides no weight or mechanical impact to the movable detector on the gimbal system this concept is exceptionally.
QWIPs and Their Applications I
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An In0.6Ga0.4As/GaAs quantum dot infrared photodetector with operating temperature up to 260K
Lin Jiang, Sheng S. Li, Nien-Tze Yeh, et al.
A high-sensitivity In0.6Ga0.4As/GaAs quantum-dot infrared photodetector (QDIP) with detection waveband in 6.7 to approximately 11.5 μm and operating temperature up to 260K under normal incident illumination has been demonstrated. The peak detection wavelength shifts from 7.6 μm to 8.4 μm when the temperature rises from 40 to 260K. The background limited performance (BLIP) detectivity (D*BLIP) measured at Vb=1.5 V, T=77K and λp = 7.6 μm was found to be 1.25 x 1010 cm-Hz1/2/W, with a corresponding responsivity of 0.22A/W. The high operating temperature is attributed to the very low dark current and long carrier lifetime in the quantum dots of this device. The results show that this QDIP can operate at high temperature without using the large band gap material such as AlGaAs or InGaP as blocking barrier to reduce the device dark current.
Development of a QWIP dual-color FPA for mine detection applications
Eric Cho, Barbara K. McQuiston, Wah Lim, et al.
Land mines, and other buried explosive devices, are widely deployed all over the world. As such, they pose a significant threat to dismounted soldiers, vehicles, and civilians. Land mines inhibit the safe movement of troops and produce chaos in countries struggling for socio-economic stability long after the cessation of hostilities. Consequently, there has been much investigation into how buried explosives might be detected and safely neutralized. Many different electro-optical and radar sensor systems have been considered for the detection of buried land mines. These include ground penetrating radars, polarization detectors, and visible/thermal infrared (IR) imagers. This paper will describe the efforts to develop a near IR/LWIR mine detection system. The core of the discussion will include highlights of a two-color LWIR QWIP sensor system designed to provide uniform, high spatial resolution, multi-color co-registered imagery and possess negligible spectral cross-talk. The current developments have been sponsored by the Defense Advanced Research Projects Agency (DARPA) for developing a visible/infrared mine detection system, which when deployed on a TUAV would increase the war fighting effectiveness of any rapid deployment force by facilitating ground penetration into hostile territory.
640x512 pixel narrowband, multiband, and broadband LWIR QWIP focal plane arrays
A 640x512 pixel, long-wavelength cutoff, narrow-band (Δλ/λ~10%) quantum well infrared photodetector (QWIP) focal plane array (FPA), a four-band QWIP FPA in 4-16 μm spectral region, and a broad-band (Δλ/λ~42%) QWIP FPA having 15.4 μm cutoff have been demonstrated. In this paper we discuss the detector designs, dark currents, quantum efficiencies, responsivities, detectivities, noise equivalent differential temperatures (NEDTs), the effect of FPA nonuniformity on performance, and the operabilities of these QWIP FPAs. In addition, we discuss the development of a very sensitive (NEDT~10.6 mK) 640x512 pixel thermal imaging camera having 9 μm cutoff.
QWIPs and Their Applications II
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Bias-controlled NIR/LWIR QWIP-based structure for night vision and see spot
Noam Cohen, Gabby Sarusi, G. Mizrachi, et al.
A novel integrated two terminal structure of Quantum Well Infrared Photodetector (QWIP) with bias controlled dual-band detection at the long wavelength infrared (LWIR) and near infrared (NIR) atmospheric windows is demonstrated. The LWIR sensor is based on a GaAs/AlGaAs standard QWIP, while the NIR sensor is based on a strained InGaAs/GaAs quantum wells structure. The InGaAs/GaAs quantum wells are embedded in a heterostructure bipolar transistor (HBT) structure, which enables high gain and rapid switching capabilities between the two spectral bands. The GaAs/AlGaAs and InGaAs/GaAs monolithic structure allows fabrication of large focal plane array (FPA) that can be operated using a standard two-terminal readout circuit (ROIC). Such FPA configuration allows simultaneous imaging of a NIR laser spot superimposed on a thermal imaging scene.
QWIP thermal imager
Olivier Cocle, Francois-Hughes Gauthier, Gilbert Quilghini, et al.
This presentation deals with the following aspects: The THALES Group has successfully manufactured sensitive arrays using QWIP technology based on AsGa techniques through THALES Research and Technology Laboratory. This QWIP technology allows the manufacturing of staring arrays for Thermal Imagers (TI) working in LWIR band (8 - 12 μm). A review of this QWIP technology is presented. The THALES Group is offering a complete range of TI for several applications, from Hand Held version to integrated versions in sight, surveillance system and gimbal. The basic choice for TI used in land applications on the battlefield remains the LWIR band. THALES Optronique has based its today strategy on very compact TI in order to allow the largest panel of applications for hand held and vehicle applications. An overview of the achieved performances and applications is presented. The current developments allowing to take the best part of the QWIP technology are also presented.
LWIR multispectral quantum well infrared photodetectors
Pradip Mitra, Francine C. Case, James H. McCurdy
This paper reports new results on multi/hyper-spectral IR detectors based on GaAs/AlGaAs multiple quantum well (MQW) materials. The wavelength tuned quantum-well IR photodetectors are obtained by patterning three-dimensional diffractive resonant optical cavities into the MQW structures. Control of the peak wavelength within the absorption band of the MQW material is achieved by adjusting the optical cavity dimensions. This approach enables highly effective optical coupling into the MQW material, produces narrow spectral response, improved detector quantum efficiency (QE) and reduced dark currents. Results are reported on the performance of multispectral detectors that are designed to operate in the 8-14 μm spectral band. Spectrally broadened MQW material absorption is achieved by engineering a triple coupled quantum well design that produces absorption bands with full width at half maximum (FWHM) of less than or equal to 3 μm. Two back-to-back MQW stacks have been employed to achieve spectral coverage in the range of 8-14 μm. As many as 52 different detector designs were fabricated on a single chip with 32x64 pixels. The spectrally tuned multispectral detector arrays exhibit excellent spectral dispersion and spectral response FWHM as narrow as ~ 0.4 μm at 8.5 μm peak wavelength. The detectors exhibit QE values in the range of 15-50%. The background limited detectivity measured at 40 K with a 295 K background and f/2.5 is in the range of (0.8-1.5)x1011 cm-Hz0.5/W. These high performance QWIPs are the first multispectral detectors fabricated over the 8-14 μm wavelength band.
Development of a visible-NIR/LWIR QWIP sensor
Eric Cho, Barbara K. McQuiston, Wah Lim, et al.
Quantum Well Infrared Photodetectors (QWIPs) based infrared focal plane arrays (FPAs) have been widely researched and investigated in the 3-5 μm and 6-20 μm wavelength ranges. The demonstrations of QWIP FPAs include single-color, dual-color and even multiple-color, as well as varieties of physical formats in the infrared range. In this paper, we discuss the research and development efforts currently undergoing at QWIP Technologies on dual-color, visible-NIR/LWIR FPAs, as an interim step for a project sponsored by DARPA (Defense Advanced Research Project Agency) to develop a four-color QWIP-based FPA. To the best of our knowledge, this is the first reported result on visible/LWIR QWIP imager, as well as the first reported GaAs PIN diode-based FPA. This device consists of a GaAs/AlGaAs based PIN diode grown on a GaAs substrate, and subsequently a stack of multiple quantum wells (MQWs), epitaxially grown on top of the PIN structure. This VISA (visible/infrared sensor array) structure is sensitive in the 500nm-890nm as well as in the 8um-12 um wavelength ranges. Very high sensitivities are observed from both visible PIN diode and LWIR QWIP; both visible and LWIR images obtained from this device are presented in this paper.
Homeland Security
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Face detection in the near-IR spectrum
Face detection is an important prerequisite step for successful face recognition. Face detection methods reported in the literature are far from perfect and deteriorate ungracefully where lighting conditions cannot be controlled. We propose a method that could potentially outperform state-of-the-art face detection methods in environments with dynamic lighting conditions. The approach capitalizes upon our near-IR skin and face detection methods reported elsewhere. It ascertains the existence of a face within a skin region by finding the eyes and eyebrows. The eye-eyebrow pairs are determined by extracting appropriate features from multiple near-IR bands. In this paper we introduce a novel feature extraction method we call dynamic integral projection. The method is relatively simple but highly effective because the processing is constrained within the skin region and aided by the near-IR phenomenology.
Using infrared sensor technology for face recognition and human identification
Recent research has demonstrated distinct advantages using thermal infrared imaging for improving face recognition performance. While conventional video cameras sense reflected light, thermal infrared cameras primarily measure emitted radiation from objects at just above room temperature (e.g., faces). Visible and thermal infrared image data collections of frontal views of faces have been on-going at NIST for over two years producing the most comprehensive database known to involve thermal infrared imagery of human faces. Rigorous experimentation with this database has revealed consistently superior recognition performance of algorithms when applied to thermal infrared particularly under variable illumination conditions. An end-to-end face recognition system incorporating simultaneous coregistered thermal infrared and visible has been developed and tested both indoors and outdoors with good performance.
Hyperspectral face recognition for homeland security
Hyperspectral sensors provide useful discriminants for human face recognition that cannot be obtained by other imaging methods. Near-infrared spectral measurements allow the sensing of subsurface tissue structure which is significantly different from person to person but relatively stable over time. The spectral properties of human tissue are also nearly invariant to changes in face orientation which bring significant degradation to most other face recognition algorithms. We examine the utility of using near-infrared hyperspectral images for the recognition of human subjects over a database of 200 subjects. The face recognition algorithm exploits spectral measurements for individual facial tissue types and combinations of facial tissue types. We demonstrate experimentally that hyperspectral imaging promises to support face recognition independent of facial expression and orientation.
Dynamic detection model and its application for perimeter security, intruder detection, and automated target recognition
Under unsteady weather conditions (gusty wind and partial cloudiness), the pixel intensities measured by infrared or optical imaging sensors may change considerably within even minutes. This makes a principal obstacle to automated target detection and recognition in real, outdoor settings. Currently existing automated recognition algorithms require strong similarity between the weather conditions of training and recognition. Empirical attempts to normalize image intensities do not lead to reliable detection in practice (e.g. for scenes with a complex relief). Also if the weather is relatively stable (weak wind, rare clouds), as short as 15-20 minutes delay between the training survey and the recognition survey may badly affect target recognition or detection, unless the targets are well separable from background. Thermal IR technologies based on invariants such as emissivity and thermal inertia are expensive and ineffective in making the recognition automated. Our approach to overcoming the problem is to take advantage of multitemporal prior surveying. It exploits the fact, that any new infrared or optical image of a scene can be accurately predicted based on sufficiently many scene images acquired previously. This removes the above severe constraints to variability of the weather conditions, whereas neither meteorological measurement nor radiometric calibration of the sensor are required. The present paper further generalizes the approach and addresses several points that are important for putting the ideas in practice. Two experimental examples: intruder detection and recognition of a suspicious target illustrate the potential of our method.
Large-format dual-broadband QWIP focal plane array imaging interferometers
Sumith V. Bandara, Sarath D. Gunapala, Francis M. Reininger, et al.
The Jet Propulsion Laboratory (JPL) is developing a 512x640-format, dual broadband, Quanum Well Infrared Photodetector (QWIP) focal plane array (FPA) for an imaging interferometer. This is a new type of imaging interferometer which is based on special Fourier-transform spectroscopy, scans interferograms digitally without moving any optical components. It is stable enough to measure fluctuating target signatures from unstable platforms, making it ideal for detecting chemical agents from a remotely piloted aircraft. These static interferometers require large-format FPAs with high uniformity and operability. QWIP technology is ideal for this instrument because it has achieved remarkable success in advancing highly uniform, highly-operability, and large-format multicolor FPAs. The FPA used in the interferometer covers the wavelength from 6-10 μm and 10-15 μm in alternative rows.
Mobile surveillance units (MSU) for border protection and homeland defense
Christopher Crandon, Paul K. Kimber
During the last 12 years the European Union (EU) has financed the new member applicant countries of Central and Eastern Europe in their preparation for joining the EU. Based on this enlargement of the EU, funding for border protection has been made available from the overall infrastructure improvement budget. Border protection was required in areas where border conflicts had taken place and to limit illegal immigration and smuggling. After 9/11 defence against terrorist activities will no doubt be added to the requirement. This paper describes the approach taken in the provision of police and para-military Mobile Surveillance Units (MSU's). This approach may also be considered for the US Homeland Defense initiative. These MSU's utilize standard road vehicles converted to use high performance military thermal imagers, such as SiGMA. In future the current, in service, MSU will require increased sensor integration and networking to cover land and coastal borders. The underlying key is affordability for the police and para-military markets while retaining the highest performance derived from the latest military standard thermal imagers.
Infrared Optics
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IR molded optics for thermal imaging
Yann M. Guimond, Yann Bellec
Umicore IR Glass is a company specialising in the production of chalcogenide glasses and moulded optics. The standard glass compositions are GASIR1 (Ge22As20Se58) and GASIR2 (Ge20Sb15Se65). These materials are transparent in the 3-5 μm and 8-12 μm bands. An industrial process has been developed to produce these two glasses with well controlled properties. The reproducibility of refractive index is for example better than 1.5 x 10-4 at 10 μm. A unique and high precision moulding technology has been developed to produce low cost chalcogenide glass lenses with high performance levels. Spherical, aspherical and asphero-diffractive lenses are manufactured with very accurate surface precision. The form defect of the moulded surfaces can be less than 0.3 μm with a typical roughness of 10 nm. When depositing an antireflection coating onto the moulded lenses, the reflection losses are reduced, raising the transmission to 98%, compared to 70% for uncoated lenses. A durable coating has also been developed as a protection for exposed lenses. Coated asphero-diffractive GASIR optics, used in infrared cameras give good quality images. The performance is comparable to that of an optical system with aspherical germanium. GASIR offers a cost-effective alternative to germanium for thermal imaging, especially for medium to high volume applications, both commercial and military.
Molded and laminated infrared imager
In previous work, laminated midwave infrare imagers were designed and manufactured. These systems used the technique of laminating a piece of plastic on to a silicon substrate lens and then single-point diamond turning an aspheric/diffractive surface on the plastic. These lenses had a focal length of 50 mm and f/# of 2.6. This paper updates the progress of the developing prototype to show initial results of compression molding the aspheric/diffractive surface onto the plastic laminated surface. The results of the previous built imagers will be compared to the ones that have been molded.
Estimating the depth of field of a complex sensor system
A complex sensor system may include imaging optics, detector assemblies, image processing, and display components. The depth of field for such systems is not always best characterized by the optical diffraction or geometric limits, therefore a more comprehensive approach may be necessary. A superset of the Rayleigh optical focus criteria, which includes the effects of all major system components, can be applied to the entire system transfer function in order to conduct a comprehensive depth of field analysis. Examples of this method will be shown for a variety of sensor configurations.
Multispectral infrared imaging optics
The design solution for a multi-spectral infrared objective is presented. Special consideration is given to the methodology and merits of material selection and design geometry. Results of the design are presented.
Manufacturing and performance evaluation of a refractive real-time MWIR hyperspectral imager
Hyperspectral imaging in the 2-5 μm band has held interest for applications in detection and discrimination of targets. Real time instrumentation is particularly powerful as a tool for characterization and field measurement. A compact, real-time, refractive MWIR hyperspectral imaging instrument has been designed, and is undergoing testing. Using a combination of dispersive and corrective elements, the system has been designed for integration and preliminary test at room temperature with passive focus correction for the cryogenic elements. The F/1.75 design supports near diffraction limited performance from 2.5 μm to 5.0 μm. This paper will review the challenges in manufacturing such a system as well as the alignment and performance data.
Infrared imaging with fiber optic bundles
Albert Ray Hilton Sr., James McCord, W. S. Thompson, et al.
Efforts have resumed to improve the image quality of infrared imaging bundles formed at AMI using the ribbon stacking method. The C4 glass has been used to reduce core size, increase packing density and improve flexibility. Ribbons are formed from unclad fiber wound on a drum with pitch, ribbon count and spacing between ribbons computer controlled. A small portion of each ribbon is compressed and fused using thin, dilute Epoxy. Unfortunately, the Epoxy, serving as a clad, absorbs most all the LWIR energy making the bundles unsuited for 8-12 μm cameras. The ribbons are removed from the drum and stacked, one on top of the other observing proper orientation to form the bundle. A typical 1 meter bundle is formed from 50-70 count ribbons for a total of 2500-4900 fibers, made from 2.5-4.9 Km of C4 fiber. Typical core diameters are 60-80 μm. Active surface area ranges from 60-70%. Infrared resolution images formed using a NIR tube camera equipped with a special relay lens demonstrates the resolution limit for the bundle. Currently, the limit is about 10 lp/mm. The bundle end is imaged in the 3-5 μm Agema 210 camera using an Amtir 1 F/1 meniscus, coated 3-5 μm. Video images taken in natural light of an individual, easily recognizable at 50 feet, will be shown. Results of careful evaluation carried out at Lockheed Martin in Orlando using a high performance Raytheon Galileo camera will be presented.
Low-cost polymer infrared imaging lens
A low-cost polymer infrared imaging lens well suited to military and security applications in the 8 to 14 μm region has been made. It has a focal length of 25 mm, and an f/number of 0.8. The design requires four aspheric or Fresnel surfaces. Remarkable performance has been demonstrated.
Optics for long-range camera modules with QWIP 640x480 detectors
In airborne applications there is a need for compact long range camera modules to be fitted into gyro-stabilized gimbals. The QWIP 640x480 detector operating in LWIR gives, with its high spatial and thermal resolution, a good performance. For the optics, long range means narrow field of view and long focal length. The challenge is to combine the narrow field of view with two wider fields of view for surveillance and still make it compact. The solution is to fold the optics. This normally gives optics with mounting difficulties, but by keeping the position requirement of each lens element low, the assembly is simplified. Design efforts combined with improved production techniques creates a solution based on diamond turned mirrors, lenses and diffractive elements. Narcissus effects are dealt with by means of customized AR coatings.
New IR detectors pig-tailed with IR fibers
Viatcheslav G. Artiouchenko, Galina V. Chekanova, Ivan Yu. Lartsev, et al.
New generation of Mercury-Cadmium-Telluride (MCT) high performance infrared radiation (IR) detectors with IR-fiber input has been developed and fabricated. This new product is originated from 25 years experience in MCT detectors and IR fiber optics technologies. Range of products includes single- and multi-element detectors designed for registration of optical signals in spectral range from 2 to 18 μm. Detectors design is integrated or modular and includes package, sensitive element, cooling system, operating temperature sensor, optical components such as narrow band-pass filter and/or lens and/or different kind of optical window, optical connection unit and fiber pig-tail or fiber cable. Cooling system options include thermoelectric cooler, long-holding time dewar filled with liquid nitrogen, Joule-Thomson micro-liquidizer and Stirling-cycle cooler. Registered infrared radiation is delivered to sensitive area of detector through either Polycrystalline InfraRed (PIR-) Fiber (4 - 18 μm) or Chalcogenide IR-glass (CIR-) Fiber (2 - 6 μm). Unique feature intrinsic to Hg1-xCdxTe (MCT) alloys to form continuous series of alloy compositions "x" with proportionally changed energy gap Eg(x,T) allows to tune spectral responsivity of detector sensitive element with ordered spectral range and hence to use every time the highest sensitive detector.
Advanced Technologies, Techniques, and Sensors
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Advances in thermographic NDT
Active thermography has gained broad acceptance as a Nondestructive Test (NDT) method for numerous in-service and manufacturing applications in the aerospace, power generation and automotive industries. However, the diffusive nature of the heat conduction process renders imaging of subsurface structures susceptible to blurring and degradation of the signal with feature depth. Although this constraint is fundamental, significant improvements in blur reduction, depth sensitivity and detection of subtle features have been achieved. These improvements have been facilitated by a Thermal Signal Reconstruction method, based on a least squares polynomial fit of the logarithm of the time history of each pixel. The process separates temporal and spatial nonuniformity noise components in the image sequence, and significantly reduces temporal noise. Time derivative images created from the reconstructed data allow detection of subsurface defects at earlier times in the sequence than conventional contrast images, significantly reducing undesirable blurring effects, and facilitating detection of low thermal contrast features that may not be detectable in the original data sequence.
Electro-optical land mine detection
Ingo Schwaetzer, Thomas Blazejewski
In the time frame from 1997 to 2001 two R&D studies were carried out by the German MoD under the responsibility from the BWB KG IV 3 and FE III 2 within the area of land mine detection: One ground based vehicle with several different sensors and an airborne version with electro-optical sensors only. In both contracts, Bodenseewerk GmbH was responsible for the real-time image-processing and signal-processing of the electro-optical sensors. In the ground-based version, BGT was subcontracted by Rheinmetall Land Systems. In the airborne version, BGT and Dornier conducted the study on a 50/50 share, but for legal reasons BGT was subcontracted by Dornier. The paper covers three topics: Basics on electro-optical land mine detection, Usable types of sensors. Primary and secondary features. Real-time signal processing. Systolic Array Processor. HW and SW architecture of experimental detection devices. Description of ground-based system, focus on electro-optical system. Images of system and scenarios. Trial results. Description of airborne system. Images of system and scenarios. Trial results.
Concordance of scores for breast infrared images by three independent investigators
Jonathan F. Head, Philip Hoekstra, Johnathan Keyserlingk, et al.
The purpose of this study was to determine whether three investigators would produce similar results when reading/scoring the same breast infrared images. They used their standard methods of analysis (subjective to semi-objective analysis). Two of the investigators submitted breast infrared images from 71 screened patients. The images were stored in a database and displayed for scoring by three investigators (two who submitted the data and one additional reader). The left and right breasts were analyzed separately. The investigators submitted their scores to the database without knowledge of the scores of the other two investigators. Overall, concordance of results among all three investgators was 76% (all three investigators' readings agreed on 107 of 141 breasts). Comparison of paired results of the three investigators resulted in 79 to 94% agreement for the six comparisons (three investigators and two breasts) with an overall agreement of 88% (371 of 424 paired comparisons). This preliminary comparison of three investigators' blinded results of breast infrared image readings from a screening population, demonstrates that breast infrared images taken at different Centers with different techniques can be interpreted by different investigators with very similar results. As the database grows there will be an increase in the number and percentage of patients with abnormal infrared images (high risk and breast cancer patients). This will allow a better and more thorough analysis of the results to refine and standardize the reading technique, and further to allow the assessment of previously untested algorithms with this unique database.
Chopping of near- and mid-infrared radiation using a curled electrostatic MEMS actuator
An electrostatic MEMS actuator known as the “Artificial Eyelid” can be used as a micromechanical chopper for IR detectors. The actuator structure consists of a curled polymer/metal film stack which is microfabricated and released from an IR transparent substrate. The film stack is uncurled by applying an electric field between the curled film and the transparent fixed electrode on the substrate. These flexible film actuators can act as IR choppers, providing transmission of radiation to the sensor elements when open (curled) and reflection when closed (uncurled). Arrays of actuators were fabricated on ITO-coated glass substrates and ranged in size from 4 x 4 mm to 7.5 x 15 mm with individual elements ranging from 250 to 500 μm on a side. Actuation for devices with average radius of curvature of 120 μ was consistently achieved at 150-170 V operation with 98-100% of the elements functioning and long lifetimes. IR chopper characteristics were measured using a blackbody source and pyroelectric detector by applying sine and square wave voltage to the actuators at a frequency of 30 Hz. The capability of the artificial eyelid for chopping near- and mid-IR radiation, including future fabrication of devices using NiCo2O4 or NiRh2O4 films for IR transparent electrodes, will be discussed.
Signal Processing In and Behind the FPA
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Advanced infrared detection and image processing for automated bat censusing
Jeffery D. Frank, Tomas H. Kunz, Jason Horn, et al.
The Brazilian free-tailed bat (Tadarida brasiliensis) forms some of the largest aggregations of mammals known to mankind. However, little is known about population sizes and nightly foraging activities. An advanced infrared (IR) thermal imaging system with a real time imaging and data acquisition system is described for censusing Brazilian free-tailed bats during nightly emergences at selected Texas caves. We developed a statistically-based algorithm suitable for counting emerging bats in columns with relative constant trajectories and velocities. Individual bats are not identified and tracked, but instead column density is calculated at intervals of 1/30th of a second and counts are accumulated based upon column velocity. Preliminary evaluation has shown this method to be far more accurate than those previously used to census large bat populations. This real-time automated censusing system allows us to make accurate and repeatable estimates of the number of bats present independent of colony size, ambient light, or weather conditions, and without causing disturbance to the colony.
Poster Session
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Composite readouts with TDI and dead elements deselection
Fiodor F. Sizov, Vladimir P. Reva, Yuri P. Derkach, et al.
For 288x4 mercury-cadmium telluride (MCT) diode array silicon readouts with deselection function, the "composite" technology approach, which simplifies the technology of their manufacturing, is considered. Both technology of n-channel CCD devices and the CMOS technology are applied, which allow to weaken considerably the technological requirements for realization of 288x4 readouts with deselection of "dead" elements (generally the 0.8 micron design rules technology is applied). It is shown that the design rules 2.5 μm for CCD technology and 2.0 design rules for CMOS technology are sufficient to realize most of functions needed for 288x4 MCT array design and manufacture. All analog functions (including TDI as the most complex function for realization in CMOS basis) are realized by CCD elements. Four-phase TDI register was realized using semi-buried channel by phosphorus ion implantation. An amplification of the output signals is realized by CMOS buffer amplifier. Decoding and deselection code storing functions are realized by digital CMOS elements. The parameters of the 288x4 silicon readout device: direct injection input circuits, 4 elements TDI function, 4 outputs; 4 MHz maximum information output frequency; 2 MHz maximum clock frequency; 3 V swing output voltage; not less than 1.6 pC maximum charge capacity per each input; 3.0 pC maximum charge capacity at multiplexor input; 75 dB dynamic band; 28 output pins.
Cooled FPAs and Applications I
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Epitaxial InSb for elevated temperature operation of large IR focal plane arrays
Tim Ashley, Theresa M. Burke, Martin T. Emeny, et al.
The use of epitaxially grown indium antimonide (InSb) has previously been demonstrated for the production of large 2D focal plane arrays. It confers several advantages over conventional, bulk InSb photo-voltaic detectors, such as reduced cross-talk, however here we focus on the improvement in operating temperature that can be achieved because more complex structures can be grown. Diode resistance, imaging, NETD and operability results are presented for a progression of structures that reduce the diode leakage current as the temperature is raised above 80K, compared with a basic p+-n-n+ structure presented previously. These include addition of a thin region of InAlSb to reduce p-contact leakage current, and construction of the whole device from InAlSb to reduce thermal generation in the active region of the detector. An increase in temperature to 110K, whilst maintaining full 80K performance, is achieved, and imaging up to 130K is demonstrated. This gives the prospect of significant benefits for the cooling systems, including, for example, use of argon in Joule-Thomson coolers or an increase in the life and/or decrease in the cost; power consumption and cool-down time of Stirling engines by several tens of per cent.
3D Imaging/Ladar
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Matching obstacle warning system LADAR parameters to helicopter maneuvering envelope
Avishay Yaniv, Vladimir Krupkin
The relation between obstacle detection LADAR parameters (Detection Range, FOV and FOR) and obstacle detection time in various flight scenarios is analyzed in this work. We show how these engineering parameters can be chosen in order to comply with the operational requirements for a minimum detection time that will enable the helicopter pilot to perform a corresponding obstacle-evasion maneuver. This method was implemented during the development of ElOp's LORD system.
Uncooled FPAs and Their Applications II
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Effect of in-plane and out-of-plane misorientation on the ferroelectric properties of thin film ferroelectric PZT infrared sensors on Si substrates
Ronald N. Vallejo, Sang-Ho Yun, Judy Z. Wu, et al.
Pb(Zr,Ti)O3 (PZT), a promising material for uncooled infrared detection, is an anisotropic perovskite with the best pyroelectric effect observed along the c-axis. Although c-axis orientated PZT films can be easily obtained on single crystal substrates with minimal lattice mismatch, it remains a challenge in practical cases when they must be grown on non-textured polymer based sacrificial coatings over Si substrates. To address this issue, we have been focused on development of thin textured MgO templates on non-textured substrates, such as amorphous SiO2/Si and polymer coated SiO2/Si, using an ion-beam-assisted deposition (IBAD) technique. C-axis-oriented multi-layered LaNiO3/Pb(Zr,Ti)O3/LaNiO3 have been achieved and the ferroelectric properties, that impact the figure of merit for IR sensors, have been characterized.
Poster Session
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Refractive GaAs microlenses monolithically integrated with InGaAs and HgCdTe photodetectors
Jozef Piotrowski, Henryk Mucha, Zbigniew Orman, et al.
Fast refractive microlenses are increasingly important as optical concentrators for uncooled infrared photodetectors. They are used in purpose to improve performance and speed of response. Refractive microlenses formed directly onto semiconductor materials draw much attention because they facilitate monolithic integration with active element of infrared photodetector. Gallium arsenide due to its superior optical and mechanical properties is a material of choice for fabrication of microlenses. We have developed process for fabrication of GaAs refractive microlenses monolithically integrated with InGaAs and HgCdTe photodetectors, both as single element devices and two-dimensional arrays. Specially designed machine tool has been used for preparation of relatively large single spherical GaAs microlenses with 0.5 mm-10 mm diameter. The microlens-detector arrays were prepared using a combination of ion milling and wet chemical etching. The typical process involves one photolithography, one ion milling and one or two chemical etching steps. More advanced procedures have also been proposed to improve quality of the lenses. The lenses can be optimized as optical concentrators for IR photodetectors with circular, square, rectangular and other geometries. This process is especially convenient for fabrication of lenses with size less than 50 μm, but larger lenses with size exceeding 300 μm can be prepared as well with some modifications of the fabrication procedures.
Uncooled FPAs and Their Applications I
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Extended short-wavelength spectral response from InGaAs focal plane arrays
Theodore R. Hoelter, Jeffrey B. Barton
InGaAs detector material used in near infrared focal plane arrays (NIR FPAs) has typically been limited in spectral response to a range from approximately 900 nm to 1700 nm. Through special processing techniques, the spectral response can be extended down through the visible spectrum and into the ultraviolet. Test results showing preliminary spectral response from 350nm to 1700 nm, responsivity, sensitivity, corrected uniformity and simultaneous imaging of NIR and visible signals will be presented along with a discussion of anticipated applications for this new sensor technology.