This work reports on the results of shore-based maritime environment and shipboard at-sea testing of the Shipboard Panoramic Electro-Optical Infrared (EO/IR) Cueing and Surveillance System (SPECSS) developed under an Office of Naval Research (ONR Code 31) Future Naval Capabilities program. The key technology enablers for the system are 25 Megapixel mid-wave infrared (MWIR) cameras that utilize III-V strained layer superlattice nBn detectors, and highly-parallel detection processing on the latest commercially available graphic processing units (GPUs). The effects of the maritime atmospheric and background conditions, as well as ship motion and line of sight stabilization, on the performance of the system will be discussed. Demonstration of highly accurate angular target cueing to other high resolution sensors will be presented.
We introduce a detection and tracking algorithm for panoramic imaging systems intended
for operations in high-clutter environments. The algorithm combines correlation- and model-based
tracking in a manner that is robust to occluding objects but without the need for a separate
collision prediction module. Large data rates associated with the panoramic imager necessitate
the use of parallel computation on graphics processing units. We discuss the queuing and
tracking algorithms as well as practical considerations required for real-time implementation.
An automated approach for detecting the presence of watercraft in a maritime environment characterized by regions of land, sea, and sky, as well as multiple targets and both water- and land-based clutter, is described. The detector correlates a wavelet model of previously acquired images with those obtained from newly acquired scenes. The resulting detection statistic outperforms two other detectors in terms of probability of detection for a given (low) false alarm rate. It is also shown how the detection statistics associated with different wavelet models can be combined in a way that offers still further improvements in performance. The approach is demonstrated to be effective in finding watercraft in previously collected short-wave infrared imagery.
KEYWORDS: Associative arrays, Data modeling, Image quality, Image compression, Super resolution, Denoising, Chemical species, Wavelets, Video, Short wave infrared radiation
We present several improvements to published algorithms for sparse image modeling with the goal of
improving processing of imagery of small watercraft in littoral environments. The first improvement
is to the K-SVD algorithm for training over-complete dictionaries, which are used in sparse
representations. It is shown that the training converges significantly faster by incorporating multiple
dictionary (i.e., codebook) update stages in each training iteration. The paper also provides several
useful and practical lessons learned from our experience with sparse representations. Results of three
applications of sparse representation are presented and compared to the state-of-the-art methods; image
compression, image denoising, and super-resolution.
The development, integration and testing of a compact system for wide-area persistence surveillance in dedicated
maritime environments is presented. The system is based around a large-format, 2560 x 512 pixel focal plane array,
high dynamic range (16 bit), mid-wave infrared (MWIR) imager operating at 30 Hz that is equipped with a 90°
horizontal field-of-view (HFOV) lens. The digitized image data is fed to a standard commercial-off-the-shelf (COTS)
workstation equipped with a graphical processing unit (GPU) that is used to perform image de-warping, non-uniformity
corrections, and algorithms for real-time object detection and tracking (NRL Harbor Tracking Software-NRLHaTS). Data is presented from several field experiments that illustrate the capabilities of the integrated system.
This work offers a comparison of broadband shortwave infrared, defined as the spectral band from 0.9 to 1.7 μm, and hyperspectral shortwave infrared imagers in a marine environment under various daylight conditions. Both imagers are built around a Raytheon Vision Systems large format (1024×1280) indium-gallium-arsenide focal plane array with high dynamic range and low noise electronics. Sample imagery from a variety of objects and scenes indicates roughly the same visual performance between the two systems. However, we show that the more detailed spectral information provided by the hyperspectral system allows for object detection and discrimination. A vessel was equipped with panels coated with a variety of paints that possessed spectral differences in the 0.9 to 1.7 μm waveband. The vessel was imaged at various ranges, states of background clutter, and times of the day. Using a standard correlation receiver, it is demonstrated that image pixels containing the paint can be easily identified. During the exercise, it was also observed that both bow waves and near-field wakes from a wide variety of vessel traffic provide a spectral signature in the shortwave infrared waveband that could potentially be used for object tracking.
This work explores the influence of head window thickness on the performance of a mid-wave infrared, panoramic
periscope imager. Our focus is on transparent spinel ceramic as the head window material. Spinel is an attractive
material for IR applications due to its good strength and transmission properties (visible through mid-wave).
However, there is some degradation in spinel transmission near the high end of the mid-wave band ( 5μm) as
the head window thickness increases. In this work we predict the relationship between head window thickness
and imager performance, as quantified by the Noise Equivalent Temperature Difference, and compare these
predictions to values estimated from experimental data. We then discuss the implications for imager design and
demonstrate a possible approach to correcting for the headwindow-induced losses. The imager used in this study
is a compact, catadioptric, camera that provides a 360o horizontal azimuth by -10o to +30o elevation field of
view and uses a 2048 x 2048, 15μm pitch InSb detector.
This paper presents a simple, fast, and robust method to estimate the blur kernel model, support size, and its
parameters directly from a blurry image. The edge profile method eliminates the need for searching the parameter
space. In addition, this edge profile method is highly local and can provide a measure of asymmetry and spatial
variation, which allows one to make an informed decision on whether to use a symmetric or asymmetric, spatially
varying or non-varying blur kernel over an image. Furthermore, the edge profile method is relatively robust to
image noise. We show how to utilize the concepts behind the statistical tools for fitting data distributions
to analytically obtain an estimate of the blur kernel that incorporates blur from all sources, including factors
inherent in the imaging system. Comparisons are presented of the deblurring results from this method to current
common practices for real-world (VNIR, SWIR, MWIR, and active IR) imagery. The effect of image noise on
this method is compared to the effect of noise on other methods.
A high-resolution midwave infrared panoramic periscope sensor system has been developed. The sensor includes an f/2.5 catadioptric optical system that provides a field of view with 360-deg horizontal azimuth and -10- to +30-deg elevation without requiring moving components (e.g., rotating mirrors). The focal plane is a 2048×2048, 15-µm-pitch InSb detector operating at 80 K. An onboard thermoelectric reference source allows for real-time nonuniformity correction using the two-point correction method. The entire system (detector-Dewar assembly, cooler, electronics, and optics) is packaged to fit in an 8-in.-high, 6.5-in.-diameter volume. This work describes both the system optics and the electronics and presents sample imagery. We model both the sensor's radiometric performance, quantified by the noise-equivalent temperature difference, and its resolution performance. Model predictions are then compared with estimates obtained from experimental data. The ability of the system to resolve targets as a function of imaged spatial frequency is also presented.
We present image data and discuss naval sensing applications of SWIR and Hyperspectral SWIR imaging in littoral and
marine environments under various light conditions. These environments prove to be challenging for persistent
surveillance applications as light levels may vary over several orders of magnitude within and from scene to scene.
Additional difficulties include imaging over long water paths where marine haze and turbulence tend to degrade
radiation transmission, and discrimination of low contrast objects under low-light and night imaging. Image data
obtained from two separate passive sensor systems, both of which are built around an RVS large format (1280 x 1024)
InGaAs FPA with high dynamic range and low noise electronics, are presented. The SWIR camera imager is equipped
with a custom 300 mm focal length f/2 narrow field-of-view (6° diagonal) refractive telescope. The Hyperspectral
imager has a custom selectable 900/1800 mm focal length telescope with corresponding 1.55°/0.79° field-of-view and fnumbers
of 3/6 respectively. The sensor uses 1280 pixels in the spatial direction and a window of 192 are used for the
spectral and operates at a nominal frame rate of 120 Hz. To assess field performance of the SWIR/Hyperspectral
imagers, comparison is made to output from a scientific grade VNIR camera and two state-of-the-art low-light sensors.
A high-resolution mid-wave infrared panoramic periscope sensor system has been developed. The sensor includes a catadioptric optical system that provides a 360° horizontal azimuth by -10° to +30° elevation field of view without requiring moving components (e.g. rotating mirrors). The focal plane is a 2048 x 2048, 15μm pitch InSb detector operating at 80K. An on-board thermo-electric reference source allows for real-time nonuniformity
correction using the two-point correction method. The entire system (detector-dewar assembly, cooler, electronics and optics) is packaged to fit in an 8" high, 6.5" diameter volume. This work describes both the system optics and electronics and presents sample imagery. We also discuss the sensor's radiometric performance, quantified by the NEDT, as a function of key system parameters. The ability of the system to resolve targets as a function of imaged spatial frequency is also presented.
The U.S. Naval Research Laboratory (NRL) established a one-way Gigabit Ethernet lasercomm link during the
Seahawk exercise in August, 2007 to transfer data ~8 miles across the inlet of San Diego Bay from Point Loma to
the Imperial Beach base camp. The data transferred over the link was from an NRL developed, wide field of view
(90 degrees), high resolution, mid-wave infrared camera operating at 30 frames per second. Details of the high
speed link will be presented as well as packet error rate data and atmospheric propagation data taken during the two
week long exercise.
In image formation and recording process, there are many factors that affect sensor performance and image
quality that result in loss of high-frequency information. Two of these common factors are undersampled
sensors and sensor's blurring function. Two image processing algorithms, including super-resolution image
reconstruction and deblur filtering, have been developed based on characterizing the sources of image
degradation from image formation and recording process. In this paper, we discuss the applications of these
two algorithms to three practical thermal imaging systems. First, super-resolution and deblurring are
applied to a longwave uncooled sensor in a missile seeker. Target resolution is improved in the flight phase
of the seeker operation. Second, these two algorithms are applied to a midwave target acquisition sensor for
use in long-range target identification. Third, the two algorithms are applied to a naval midwave distributed
aperture sensor (DAS) for infrared search and track (IRST) system that is dual use in missile detection and
force protection/anti-terrorism applications. In this case, super-resolution and deblurring are used to
improve the resolution of on-deck activity discrimination.
Prototype 2-, 3-, and 4- band long wave infrared (LWIR) focal plane arrays (FPA) for missile defense applications have recently been constructed to enhance target discrimination in space-based interceptor seekers. To address issues related to target identification such as algorithm choice and band number, this study created synthesized, optimized (using a genetic algorithm) image cubes (8- 12 mm) of targets and backgrounds compatible with expected mid-course defense scenarios and current multicolor sensors. Each candidate band was weighted using an interacting band edge model for 2-, 3- or 4- band sensors, consistent with a DRS multi-color HgCdTe LWIR FPA. Whitening the binned cubes and assigning red, green, blue colors directly to the whitened data set can prominently display and identify targets. Modified target signatures applied in matched filters searches and spectral angle maps autonomously searched for targets in the synthetic binned image cubes. Target discrimination diminished with decreasing target temperature and/or increasing distance between sensor and targets due to mixing subpixel target spectra with noise background. Spectral angle maps identified target temperatures and materials substantively better than the matched filter in this particular study. Target material and temperature identification improved by increasing number of bands, with greatest improvement for 3 bands relative to 2 bands. Extending detector sensitivity to 6-14 mm failed to improve target identification. This is the first study to systematically examine target identification in synthetic images cubes, consistent with missile defense scenarios and current multi-sensor technology.
The Navy faces an ever evolving threat scenario, ranging from sub-sonic sea skimming cruise missiles to newer, unconventional threats such as that experienced by the USS Cole. Next generation naval technology development programs are developing “stealthy” ships by reducing a ships radar cross section and controlling electromagnetic emissions. To meet these threat challenges in an evolving platform environment, ONR has initiated the “Wide Aspect MWIR Array” program. In support of this program, Raytheon Vision Systems (RVS) is developing a 2560 X 512 element focal plane array, utilizing Molecular Beam Epitaxially grown HgCdTe on silicon detector technology. RVS will package this array in a sealed Dewar with a long-life cryogenic cooler, electronics, on-gimbal power conditioning and a thermal reference source. The resulting sub system will be a component in a multi camera distributed aperture situation awareness sensor, which will provide continuous surveillance of the horizon. We will report on the utilization of MWIR Molecular Beam Epitaxial HgCdTe on Silicon material for fabrication of the detector arrays. Detector arrays fabricated on HgCdTe/Si have no thermal expansion mismatch relative to the readout integrated circuits. Therefore large-area focal plane arrays (FPAs) can be developed without concern for thermal cycle reliability. In addition these devices do not require thinning or reticulation like InSb FPAs to yield the high levels of Modulation Transfer Function (MTF) required by a missile warning sensor. HgCdTe/Si wafers can be scaled up to much larger sizes than the HgCdTe/CdZnTe wafers. Four-inch-diameter HgCdTe/Si wafers are currently being produced and are significantly larger than the standard 1.7 inch x 2.6 inch HgCdTe/CdTe wafers. The use of Si substrates also enables the use of automated semiconductor fabrication equipment.
Programs in both the U.S. and Britain are attempting to apply staring array technology to the ship-board infrared search and track (SBIRST) problem. A prime objective is to speed processing time, the previous generation of 360 deg scanners having a refresh rate of only 0.5-1.0 Hz. Another objective is to enhance sensitivity using much longer integration times. An impediment, though, is that if all pixels of resolution angle ∅ were to be viewed simultaneously with dedicated detectors each of width w, the total net length of detector material would then have to be very large: 2πw/∅ = 1.57 m = 60" for 100 μRad resolution and 25 μm detectors. So the application of staring array technology to horizon surveillance needs some form of wide viewing technique involving a combination of asymmetric resolution, reduced resolution, split optics or LOS stepping. The present paper suggests that conventional NEI is not the preferred unit of measure for guiding design choices but that instead a form of BLIP S/N can be both simple and intuitive. This S/N unit of measure is used to compare the two main choices for how to adapt staring technology to the horizon surveillance problem.
To achieve enhanced target discrimination, prototype three- band long wave infrared (LWIR) focal plane arrays (FPA) for missile defense applications have recently been constructed. The cutoff wavelengths, widths, and spectral overlap of the bands are critical parameters for the multicolor sensor design. Previous calculations for sensor design did not account for target and clutter spectral features in determining the optimal band characteristics. The considerable spectral overlap and correlation between the bands and attendant reduction in color contrast is another unexamined issue. To optimize and simulate the projected behavior of three-band sensors, this report examined a hyperspectral LWIR image cube. Our study starts with 30 bands of the LWIR spectra of three man-made targets and natural backgrounds that were binned to 3 bands using weighted band binning. This work achieves optimal binning by using a genetic algorithm approach and the target-to-clutter-ratio (TCR) as the optimization criterion. Another approach applies a genetic algorithm to maximize discrimination among the spectral reflectivities in the Non-conventional Exploitation Factors Data System (NEFDS) library. Each candidate band was weighted using a Fermi function to represent four interacting band edges for three- bands. It is found that choice of target can significantly influence the optimal choice of bands as expressed through the TCR and the Receiver Operator Characteristic curve. This study shows that whitening the image data prominently displays targets relative to backgrounds by increasing color contrast and also maintains color constancy. Three-color images are displayed by assigning red, green, blue colors directly to the whitened data set. Achieving constant colors of targets and backgrounds over time can greatly aid human viewers in the interpretation of the images and discriminate targets.
Benjamin Shanabrook, W. Barvosa-Carter, Robert Bass, Brian Bennett, J. Boos, William Bewley, Allan Bracker, James Culbertson, E. Glaser, Walter Kruppa, R. Magno, W. Moore, Jerry Meyer, B. Nosho, Doewon Park, P. Thibado, M. Twigg, R. Wagner, James Waterman, Lloyd Whitman, Ming Yang
Heterostructures formed from III-V semiconductors with the 6.1 angstroms lattice spacing (InAs, GaSb, AlSb and related alloys) have attracted significant interest because of their potential to define a new `state of the art' in applications including 100 GHz high-speed logic circuits, terahertz transistors, sensitive infrared detectors and mid-infrared semiconductor lasers. In this paper, we describe the ongoing work at the Naval Research Laboratory to develop the materials growth and fabrication technology for a variety of 6.1 angstroms-based devices which have the potential to revolutionize infrared optoelectronics and low-power, high- speed electronics.
To achieve the DoD objective of low cost high performance infrared focal plane arrays a manufacturing technique is required which is intrinsically flexible with respect to device configuration and cutoff wavelength and easily scaleable with respect to volume requirements. The approach adopted is to fully develop the technology of molecular beam epitaxy (MBE) to a level where detector array wafers with a variety of configurations can be fabricated with first pass success at a reduced cost. As a vapor phase process, MBE lends itself directly to: (1) the inclusion of real-time monitoring and process control, (2) a single or multiple wafer growth mode, (3) nearly instantaneous changes in growth parameters. A team has been assembled to carry out the program. It is composed of four industrial organizations -- Rockwell International, Hughes Aircraft Company, Texas Instruments, and Lockheed-Martin, and a university -- Georgia Tech Research Institute. Since team members are committed suppliers and users of IRFPAs, technology transfer among team members is accomplished in real-time. The technical approach has been focused on optimizing the processes necessary to fabricate p-on-n HgCdTe double layer heterostructure focal plane arrays, reducing process variance, and on documenting flexibility with respect to cutoff wavelength. Two device structures have been investigated and fabricated -- a 480 by 4 and a 128 by 128.
We review recent progress in the development of quantum confined structures based on the InAs-GaSb-AlSb family of semiconductors. The results of transport and quantum transport experiments are summarized to illuminate band structure features and carrier scattering mechanisms that are key to device applications. The unique band structure engineering possibilities enabled by the presence of L-valleys in the conduction band are explored, as well as, the general progress in band structure calculations and modeling of complex multi-layers. A primary emphasis is the flexibility of the InAs-GaSb-AlSb material system as the basis for a wide variety of E-O modulators, frequency doublers, infrared diode lasers, and other devices.
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