Proceedings Volume 3703

Passive Millimeter-Wave Imaging Technology III

Roger M. Smith
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Proceedings Volume 3703

Passive Millimeter-Wave Imaging Technology III

Roger M. Smith
View the digital version of this volume at SPIE Digital Libarary.

Volume Details

Date Published: 14 July 1999
Contents: 4 Sessions, 19 Papers, 0 Presentations
Conference: AeroSense '99 1999
Volume Number: 3703

Table of Contents

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Table of Contents

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  • PMMW Imaging Systems
  • PMMW Component Technology
  • PMMW Modeling and Phenomenology
  • PMMW Resolution Enhancement/Super-Resolution
  • PMMW Component Technology
PMMW Imaging Systems
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Radiometric one-second camera (ROSCAM) airborne evaluation
Roger M. Smith, Bryce M. Sundstrom, Byron W. Belcher, et al.
The rapidly developing market for passive millimeter-wave imaging cameras with a frame time of one second or less includes several commercial as well as military applications. A mechanical scanning antenna system has demonstrated the ability to meet a one second frame time for a 1000 pixel scene, using only one receiving channel. That camera has been updated to provide an airborne imaging capability, in both a raster scanning mode, and a cross- track in-light mode. The results of a helicopter test program will be described.
Compact real-time (video rate) passive millimeter-wave imager
Roger Appleby, Rupert N. Anderton, Sean Price, et al.
This paper describes a novel real time mechanically scanned passive millimeter wave imager. This imager produces a field of view of 40 degree(s) X 20 degree(s) with diffraction limited performance and a 25 Hz frame update rate. It is relatively inexpensive because the scene is imaged using 32 direct detection receivers with a frequency of operation from 28 - 33 GHz. The compact antenna uses polarization techniques to fold the beam and is constructed from readily available low cost materials.
140-GHz passive millimeter-wave video camera
Larry Yujiri, Steven W. Fornaca, Bruce I. Hauss, et al.
TRW has recently developed InP low noise amplifiers operating at 140 GHz. Similar to the evolution of 94 GHz GaAs technology, this lays the foundation for the development of a 140 GHz MMIC receiver for use in a next generation passive millimeter-wave video camera capable of generating a real time display of the imaged scene. The advantages of going to 140 GHz, and the use of InP technology, will be discussed.
W-band real-time passive millimeter-wave imager for helicopter collision avoidance
A w-band passive millimeter imager is proposed for use on a helicopter platform. The atmospheric transmission through fog and rain is much higher in the millimeter wave band than it is in the visible or infrared regions of the spectrum. This property enables passive millimeter wave imaging systems to offer recognizable imagery in adverse weather conditions. Furthermore, as the technique is based on incoherent imaging, it can be used in environments where it may be difficult for radar to process data into recognizable imagery. The 30 cm diameter real-time passive millimeter wave imager described here will have a radiometric sensitivity of around 1 degree(s)C and a radiation bandwidth of 80 GHz to 105 GHz. The system is based on the DERA mechanical scanning passive millimeter wave imager architecture.
Radarometer sensor: simultaneous active and passive imaging using a common antenna
Darryl G. Huddleston, James Savage, Bryce M. Sundstrom, et al.
The ability to obtain simultaneous active and passive millimeter wave images using a common antenna has numerous DOD as well as commercial applications. Radiometric and radar images are not new, nor are simultaneous passive and active images of a common scene. The feature that is unique to the radarometer concept is simultaneous use of the same antenna by a radar and a radiometer, operating in the same frequency band at a nominal pixel scanning rate of 1,000 per second. The radarometer sensor is capable of operating in both the passive and active modes either individually, in time sequence, or simultaneously. The radarometer uses a common high-speed mechanically scanned antenna aperture capable of generating active and passive millimeter wave images simultaneously. The important feature of the radarometer design that allows simultaneous active and passive operation in the use of an RF diplexer which separates the signals associated with the radar and radiometer modes. The typical frequency separation displacement is 5 GHz, at a nominal operating frequency of 95 GHz. The results of measurements performed on an engineering test unit will be described.
PMMW Component Technology
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Design of a novel PMMW imaging system
Vladimir A. Manasson, Lev S. Sadovnik, Robert M. Mino
We present a design of a novel PMMW Imaging system that utilizes special arrangement of N equals 36 focal plane elements. While horn antennas continuously rotate around the center of the focal plane, N MMW radiometric receivers are fixed. All together they generate N X N PMMW image. We discuss main feature of the proposed design and specifics associated with the corresponding MMW coupling.
Sensor fusion with passive millimeter-wave and laser radar for target detection
Chun-Shin Lin, Sengvieng A. Amphay, Bryce M. Sundstrom
Advanced sensors and guidance techniques are required in killing mobile offensive and defensive systems. Many different sensors such as radar, video camera, laser radar (LADAR), millimeter wave systems, infrared imagers, acoustic sensors, etc. are available for such usage. However, no single sensor provides completely satisfactory capabilities. Since some sensors have complementary capabilities, integration of multiple sensors for kill can relax the task difficulty and provide more reliable results. The use of multiple sensors can also reduce the possibility of being defeated by countermeasures. In this study, we investigated the framework and investigated potential techniques for integration and fusion of information from passive millimeter wave (PMMW) and LADAR systems. The focus has been on target detection. The PMMW is used to detect metal objects and the LADAR examines those regions of interest for other evidence of existence of a target. Advances obtained by integrating these two sensors include reduction of task complexity and improvement of reliability, both due to efficient localization of regions of interest from the PMMW. Since PMMW possesses weather penetration capabilities through fog, cloud, smoke, etc., the combined system has a near-all-weather capability. A LADAR provides 3D information, and it should be used as the primary sensor for target acquisition upon target detection. The framework of the fusion is based on the Dempster-Shafer decision method. The fusion may be done in the algorithm level and sensor level. With the Dempster-Shafer method as the framework, new sensors or new decision components can be easily integrated.
Multiple-ray passive radiovision systems of millimeter-wave range
Valeri V. Gladun, Yuri A. Pirogov, Vladimir S. Ivanov, et al.
Methods of mathematical modeling of multiple rays radiovision systems of image formation with antenna pattern distortion compensation in millimeter wavelength range are developed and improved at the Faculty of Physics of Moscow State University. At the moment intensive experimental investigations of the working multiple rays radiovision systems on the base of phased antenna array and radio- optical systems with the rules and sensors frames are carried out. In the report the possibilities of developed dialog program complex for multiple rays systems of image registration and formation with following antenna pattern distortions compensation are shown on the base of the real data.
PMMW Modeling and Phenomenology
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Millimeter-wave brightness temperatures of military vehicles
Joseph Nemarich, Thomas W. Cassidy, R. Shiner, et al.
Millimeter wave (MMW) radiometers operating at 97 and 140 GHz were used to obtain passive MMW images and brightness temperatures of military vehicles at various altitudes and depression angles. The line-scanning radiometer system used for the measurements is described, and several passive MMW images are presented. The upper-bound MMW brightness temperatures of a number of different types of vehicles in an open area were determined and shown to have similar values at various depression angles.
Measurement of nadir and near-nadir 94-GHz brightness temperatures of several tactical-scene clutter types
The authors present 94-GHz radiometric brightness temperatures of various clutter materials at nadir. The clutter materials measured include field vegetation, asphalt pavement, and an asphalt shingle roof and data is presented for each clutter type. We also report measurements that quantify the effect of water on the brightness temperature of metal. These measurements were made by adding calibrated quantities of water to a metal plate while recording the plate's millimeter-wave brightness temperature. Off-nadir data out to 45 deg is also presented for the field vegetation and asphalt pavement. Using a simple rough scattering model for the materials, we made estimates of the emissivity of the field vegetation and asphalt. The emissivity of the roof was determined by measuring its brightness temperature as it was heated.
Coherent effects in passive centimeter- and millimeter-wave imaging for landmine detection
Coherent effects in passive centimeter and millimeter wave emission used to detect landmines is investigated. The work concentrates on the modeling of the radiation temperatures of buried metal and plastic plates. A two interface model, which uses the dielectric constants of the media, is used to predict the radiation temperatures. Conclusions are that the use of coherence effects may complement the standard passive radiometry techniques for the detection of buried metal and plastic. This technique could extend the useful bandwidth, over which a system may operate, by a factor of two to three beyond that of standard radiometry.
Microwave spectroscopy of chemical warfare agents: prospects for remote sensing
Alan C. Samuels, James O. Jensen, Richard D. Suenram, et al.
The high level of interest in the sensor development community in millimeter wave technology development demonstrates the potential for several multipurpose applications of millimeter wave sensors. The potential for remote sensing of hazardous chemical materials based on their millimeter wave rotational signatures is yet another possible applications, offering certain distinct advantages over FTIR remote sensing. The high specificity of the rotational spectra to the molecular structures affords the capability of detecting chemical warfare (CW) agents and degradation products in complex mixtures including water vapor and smoke, an important consideration in military applications. Furthermore, the rotational modes are not complicated by electronic or vibrational transitions, reducing the potential for false alarms. We have conducted microwave spectroscopic measurements on two CW nerve agents (sarin and soman) and one blister agent (H-mustard). The assignment of the observed band furnishes us with an extremely accurate tool for predicting the rotational spectrum of these agents at any arbitrary frequency. By factoring in the effects of pressure (Lorentzian broadening and intensity reduction), we present the predicted spectral signatures of the CW agents in the 80 - 300 GHz region. This frequency regime is important for atmospheric monitoring as it exploits the wide bandwidth capability of millimeter wave sensors as well as the atmospheric windows that occur in this region.
Millimeter-wave imaging of thermal and chemical signatures
Nachappa Gopalsami, Apostolos C. Raptis
Development of a passive millimeter-wave (mm-wave) system is described for remotely mapping thermal and chemical signatures of process effluents with application to arms control and nonproliferation. Because a large amount of heat is usually dissipated in the air or waterway as a by-product of most weapons of mass destruction facilities, remote thermal mapping may be used to detect concealed or open facilities of weapons of mass destruction. We have developed a focal-plane mm-wave imaging system to investigate the potential of thermal mapping. Results of mm-wave images obtained with a 160-GHz radiometer system are presented for different target scenes simulated in the laboratory. Chemical and nuclear facilities may be identified by remotely measuring molecular signatures of airborne molecules emitted from these facilities. We have developed a filterbank radiometer to investigate the potential of passive spectral measurements. Proof of principle is presented by measuring the HDO spectral line at 80.6 GHz with a 4-channel 77 - 83 GHz radiometer.
PMMW Resolution Enhancement/Super-Resolution
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Resolution and resolution improvement of passive millimeter-wave images
Joseph D. Silverstein
Measured and simulated passive millimeter-wave images of a simple target pattern were processed with Two-Mu, a linear, noniterative restoration algorithm. Decisions about whether the RAM pattern objects were sufficiently visible against a metallic background to be recognized were made by visually inspecting the images. This allowed quantitative measures to be made of the resolution improvement afforded by Two-Mu, as a function of scene oversampling for various target ranges and radiometer apertures. improvements by factors up to 1.25 and 1.45 were found for images and analog plots, respectively, of cuts through images, respectively.
Role of over-sampled data in superresolution processing and a progressive up-sampling scheme for optimized implementations of iterative restoration algorithms
Malur K. Sundareshan, Pablo Zegers
Super-resolution algorithms are often needed to enhance the resolution of diffraction-limited imagery acquired from certain sensors, particularly those operating in the millimeter-wave range. While several powerful iterative procedures for image superresolution are currently being developed, some practical implementation considerations become important in order to reduce the computational complexity and improve the convergence rate in deploying these algorithms in applications where real-time performance is of critical importance. Issues of particular interest are representation of the acquired imagery data on appropriate sample grids and the availability of oversampled data prior to super-resolution processing. Sampling at the Nyquist rate corresponds to an optimal spacing of detector elements or a scan rate that provides the largest dwell time (for scan- type focal plane imaging arrays), thus ensuring an increased SNR in the acquired image. However, super-resolution processing of this data could produce aliasing of the spectral components, leading not only to inaccurate estimates of the frequencies beyond the sensor cutoff frequency but also corruption of the passband itself, in turn resulting in a restored image that is poorer than the original. Obtaining sampled image data at a rate higher than the Nyquist rate can be accomplished either during data collection by modifying the acquisition hardware or as a post-acquisition signal processing step. If the ultimate goal in obtaining the oversampled image is to perform super- resolution, however, upsampling operations implemented as part of the overall signal processing software can offer several important benefits compared to acquiring oversampled data by hardware methods (such as by increasing number of detector elements in the sensor array or by microscanning). In this paper, we shall give a mathematical characterization of the process of image representation on a sample grid and establish the role of oversampling by studying the dynamics of information transfer during image restoration. A new progressive upsampling procedure is presented that provides optimized implementations of iterative superresolution. Finally, the super-resolution performance of the overall scheme that combines the progressive upsampling technique with a maximum likelihood restoration algorithm will be demonstrated quantitatively by presenting processed passive millimeter-wave imagery data.
Nonuniformity correction and restoration of passive millimeter-wave images
This paper discusses methods of improving the quality and resolution of passive mm-wave images, particularly those obtained using the DERA MITRE imager and the more recent MERIT imager. This later real time imager consists of some novel optics followed by a conical scanner in the form of a disk rotating about an axis through its center and tilted with respect to its normal. A horizontal array of receivers is scanned such that each receiver performs a conical scan pattern in the scene. The resulting image which has a 40 degree by 20 degree field of view, consists of a series of circles whose centers are uniformly displaced horizontally. Each receiver is calibrated initially using a two point correction but then drifts in time and a scene based correction is applied. Following this pre-processing the images are superresolved using nonlinear restoration techniques. These various processes are described and images presented.
Problem of the radiovision system resolution improvement in millimeter-wave range
Yuri A. Pirogov, Magdy F. Attia, Isaiah M. Blankson, et al.
At the Faculty of Physics of Moscow State University experimental researches of the working radiovision systems on the base of phased antenna array and radio optical systems with the sensors rules are carried out. Since 1980 the system of Sun radio observation in 3-mm wavelength range created by the specialists of Bauman Moscow State Technical University is exploited. Investigations in the mathematical modeling of image formation systems in wide wavelength range with different receiving schemes and with distortion compensation task solution and super-resolution are conducted by mathematician and physicists.
Problem of the sun radiovision system superresolution in 3-mm-wavelength range
Evgeni N. Terentiev, Yuri A. Pirogov, Valeri V. Gladun, et al.
Wide usage of new approaches in radiovision for the sake of radio astronomical investigation is expected as they can fix image independently of the atmosphere state. New ranges of radiation registration promise to show new processes and phenomena in astronomy. Existing Sun radiovision system doesn't give possibility to resolve the details of the processes on the Sun fine structure. Near zone of the radiotelescope is so big that it doesn't allow to measure Sun radiovision system Point Spread Function (PSF) by the ground based methods. By the other words, it's impossible to estimate minimal point object (PSF) that could be seen on the Sun by ground based methods. The task of radiovision system PSF estimation was solved valuing the Sun's edge in the assumption of PSF circular symmetry. In the paper the possibilities of developed dialog complex of complicated Sun's radio observing system modeling with subsequent antenna pattern distortions compensation by linear and nonlinear methods.
PMMW Component Technology
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Passive millimeter-wave camera images: current and future
Lee Mirth, Al Pergande, Dayton D. Eden, et al.
Lockheed Martin and Intelligent Machine Technology are working to build a demonstration system for the Department of Justice and the Air Force Research Laboratory that can be extended to take advantage of rapidly moving semiconductor improvements. Our current radiometer modules use a PIN switch for the Dicke calibration function followed by multiple low noise amplifier stages, a Schottky detector and a video amplifier. Sensitivity of such modules is primarily a function of the insertion loss and noise figure of the front end MMIC circuits. Processing improvements at Lockheed Martin and refined chip design will result in a 3 dB improvement in the effective noise figure within the next year. Imaging is also greatly improved by achieving greater effective bandwidth and higher operating frequency. Whereas present modules operate from 80 to 90 GHz, MMIC improvements will provide for operation up to 140 GHz with a doubling of the bandwidth in the near term. Receiver operation up to 540 GHz has also been demonstrated at other labs.