Showing papers in "Proceedings of SPIE in 1996"

MSTAR extended operating conditions: a tutorial

Abstract: One key advantage of the model-based approach for automatic target recognition (ATR) is the wide range of targets and acquisition scenarios that can be accommodated without algorithm re-training. This accrues from the use of predictive models which can be adjusted to hypothesized scenarios on-line. Approaches which rely on measured signature exemplars as the source of reference data for signature matching are constrained to those scenarios represented in the reference data base. The moving and stationary target recognition (MSTAR) program will advance the state-of-the-art in model-based ATR by developing, evaluating, and testing algorithm performance against a set of extended operating conditions (EOCs) designed to reflect real-world battlefield scenarios. In addition to full 360 deg target aspect coverage over a range of depression angles, the EOCs include variations in squint angle, target articulation and configurations, obscuration due to occlusion and/or layover, and intra-class target variability. These conditions can have a profound impact on the nature of the target signature, necessitating the development of explicit prediction and reasoning algorithms to provide robust target recognition. This paper provides a tutorial description of the impact of the MSTAR EOCs on SAR target signatures. A brief background discussion of the SAR imaging process is presented first. This is followed by a description of the impact of each EOC category on the target signature along with synthetic imagery examples to illustrate this impact.

Development of VHF CARABAS II SAR

Abstract: There is an increasing interest in imaging radar systems operating at low frequencies. Examples of military and civilian applications are detection of stealth-designed man- made objects, targets hidden under foliage, biomass estimation, and penetration into glaciers or ground. The developed CARABAS technology is a contribution to this field of low frequency SAR imagery. The used wavelengths offer a potential of penetration below the upper scattering layer in combination with high spatial resolution. The first prototype of the system (CARABAS I) has been tested in environments ranging from rain forests to deserts, collecting a considerably amount of data often in parallel with other SAR sensors. The work on data analysis proceeds and results obtained so far seem promising, especially for application in forested regions. The experiences gained are used in the development of a new upgraded system (CARABAS II), which is near completion and initial airborne radar tests for system verifications followed by some major field campaign are scheduled to take place during 1996. This paper will summarize the CARABAS I system characteristics and system performance evaluation. The major imperfections discovered in the radar functioning will be identified, and we explain some of the modification made in the system design for CARABAS II. A new algorithm for future real-time CARABAS data processing has been derived, with a structure well-suited for a multi-processor environment. Motion compensation and radio frequency interference mitigation are both included in this scheme. Some comments on low frequency SAR operation at UHF-based versus VHF-band will be given.

Pfinder: real-time tracking of the human body

Abstract: Pfinder is a real-time system for tracking and interpretation of people. It runs on a standard SGI Indy computer, and has performed reliably on thousands of people in many different physical locations. The system uses a multiclass statistical model of color and shape to segment a person from a background scene, and implements heuristics which can find and track people's head and hands in a wide range of viewing conditions. Pfinder produces a real- time representation of a user useful for applications such as wireless interfaces, video databases, and low-bandwidth coding, without cumbersome wires or attached sensors.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Computer-vision-based registration techniques for augmented reality

Abstract: Augmented reality is a term used to describe systems in which computer-generated information is superimposed on top of the real world; for example, through the use of a see-through head-mounted display. A human user of such a system could still see and interact with the real world, but have valuable additional information, such as descriptions of important features or instructions for performing physical tasks, superimposed on the world. For example, the computer could identify objects and overlay them with graphic outlines, labels, and schematics. The graphics are registered to the real-world objects and appear to be “painted” onto those objects. Augmented reality systems can be used to make productivity aids for tasks such as inspection, manufacturing, and navigation. One of the most critical requirements for augmented reality is to recognize and locate real-world objects with respect to the person’s head. Accurate registration is necessary in order to overlay graphics accurately on top of the real-world objects. At the Colorado School of Mines, we have developed a prototype augmented reality system that uses head-mounted cameras and computer vision techniques to accurately register the head to the scene. The current system locates and tracks a set of preplaced passive fiducial targets placed on the real-world objects. The system computes the pose of the objects and displays graphics overlays using a see-through head-mounted display. This paper describes the architecture of the system and outlines the computer vision techniques used.

Guide to using field programmable gate arrays (FPGAs) for application-specific digital signal processing performance

Abstract: FPGAs have become a competitive alternative for high performance DSP applications, previously dominated by general purpose DSP and ASIC devices. This paper describes the benefits of using an FPGA as a DSP co-processor, as well as, a stand-alone DSP engine. Two case studies, a Viterbi decoder and a 16-tap FIR filter are used to illustrate how the FPGA can radically accelerate system performance and reduce component count in a DSP application. Finally, different implementation techniques for reducing hardware requirements and increasing performance are described in detail.

Archiving, indexing, and retrieval of video in the compressed domain

Abstract: Fast and efficient storage, indexing, browsing, and retrieval of video is a necessity for the development of various multimedia database applications. This can be achieved by analyzing the video directly in the compressed domain, thereby avoiding the overhead of decompressing video into individual frames in the pixel domain. Our compressed domain parsing of video performs shot change detection and motion detection using the data readily accessible from MPEG, with minimal decoding. Key frames are identified and are used for indexing, retrieval, and browsing. In this paper, we describe feature extraction and key frame indexing and retrieval techniques that are directly applicable to compressed video. The features are derived form the available DCT, macroblock, and motion vector information and the techniques enable fast parsing and archiving of video.

Comparison of automatic video segmentation algorithms

Abstract: While several methods of automatic video segmentation for the identification of shot transitions have been proposed, they have not been systematically compared. We examine several segmentation techniques across different types of videos. Each of these techniques defines a measure of dissimilarity between successive frames which is then compared to a threshold. Dissimilarity values exceeding the threshold identify shot transitions. The techniques are compared in terms of the percentage of correct and false identifications for various thresholds, their sensitivity to the threshold value, their performance across different types of video, their ability to identify complicated transition effects, and their requirements for computational resources. Finally, the definition of a priori set of values for the threshold parameter is also examined. Most techniques can identify over 90% of the real shot transitions but have a high percentage of false positives. Reducing the false positives was a major challenge, and we introduced a local filtering technique that was fairly effective.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Order N^2 log(N) backprojector algorithm for focusing wide-angle wide-bandwidth arbitrary-motion synthetic aperture radar

Abstract: A new, fast algorithm for synthetic aperture radar (SAR) image formation is introduced. The algorithm is based on a decomposition of the time domain backprojection technique. It inherits the primary advantages of time domain backprojection: simple motion compensation, simple and spatially unconstrained propagation velocity compensation, and localized processing artifacts. The computational savings are achieved by using a divide-and-conquer strategy of decomposition, and exploiting spatial redundancy in the resulting sub-problems. The decomposition results in a quadtree data structure that is readily parallelizable and requires only limited interprocessor communications. For a SAR with N aperture points and an N by N image area, the algorithm is seen to achieve O(N2logN) complexity. The algorithm allows a direct trade between processing speed and focused image quality.

General data fusion for estimates with unknown cross covariances

Abstract: In this paper we present a new theoretic framework for combining sensor measurements, state estimates, or any similar type of quantity given only their means and covariances. The key feature of the new framework is that it permits the optimal fusion of estimates that are correlated to an unknown degree. This framework yields a new filtering paradigm that avoids all of the restrictive independence assumptions required by the standard Kalman filter, though at the cost of reduced rates of convergence for cases in which independence can be established.

Shape recognition of irregular objects

Abstract: A new approach to object recognition is proposed. The main concern is on irregular objects which are hard to recognize even for a human. The recognition is based on the contour of an object. The contour is obtained with morphological operators and described with a Freeman chain code. The chain code histogram (CCH) is calculated from the chain code of the contour of an object. For an eight-connected chain code an eight dimensional histogram, which shows the probability of each direction, is obtained. The CCH is a translation and scale invariant shape measure. The CCH gibes only an approximation of the object's shape so that similar objects can be grouped together. The discriminatory power of the CCH is demonstrated on machine-printed text and on true irregular objects. In both cases it is noted that similar objects are grouped together. The results of experiments are good. It has been shown that similar objects are grouped together with the proposed method. However, the sensitivity to small rotations limits the generality of the method.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Micromolding: a powerful tool for large-scale production of precise microstructures

Abstract: In recent years a number of micro machining processes have been developed suitable for the realization of industrial process applications, whereby the LIGA technique is considered to be one of the most promising and flexible technologies for the large scale fabrication of three- dimensional microstructure products. LIGA is based on the combination of deep lithography, and electroforming to realize mold inserts with high accuracy for the mass fabrication of microcomponents made from plastic material. The present report deals with the development of micromolding technologies which are applied at IMM. Specifically they are focused on the small dimensions of the molded microstructures, the high aspect ratio, and the demand for sub-micron precision. This includes the technical implementation of molding processes, the production of suitable micro mold inserts, the investigation in simulation software, the screening of polymer materials, ceramics, metallic powders or preceramic polymers and the development of quality qualification systems. The potential of micro molding processes will be demonstrated by presenting a variety of applications like micro gear wheels, micro pumps, micro optical components, splices and connectors, waveguides, optical gratings and components for chemical and biological micro reactors.

New test structures and techniques for measurement of mechanical properties of MEMS materials

Abstract: This paper presents techniques and procedures for addressing the three major problems of mechanical testing of the thin films used in surface micromachined microelectromechanical systems--specimen handling, friction, and strain measurement. The polysilicon tensile specimens are fabricated with two supporting side strips on silicon wafers at the Microelectronic Center of North Carolina. The tensile specimen is released by etching away the wafer, and the two support strips are cut after the specimen is glued in the test machine. Friction is reduced by a linear air bearing in the load train, and strain is measured with a noncontacting technique based on laser interferometry between two gold lines on the tensile specimen. The Young's modulus of polysilicon is 170 +/- 7 GPa and the strength is 1.21 +/- 0.16 GPa from a series of 29 tests. preliminary measurements have been made of Poisson's ratio and the fatigue behavior, and an attempt is underway to measure the fracture toughness.

Concealed explosive detection on personnel using a wideband holographic millimeter-wave imaging system

Abstract: A novel wideband millimeter-wave imaging system is presently being developed at Pacific Northwest National Laboratory (PNNL) that will allow rapid inspection of personnel for concealed explosives, handguns, or other threats. Millimeter-wavelength electromagnetic waves are effective for this application since they readily penetrate common clothing materials, while being partially reflected from the person under surveillance as well as any concealed items. To form an image rapidly, a linear array of 128 antennas is used to electronically scan over a horizontal aperture of 0.75 meters, while the linear array is mechanically swept over a vertical aperture of 2 meters. At each point over this 2-D aperture, coherent wideband data reflected from the target is gathered using wide-beamwidth antennas. The data is recorded coherently, and reconstructed (focused) using an efficient image reconstruction algorithm developed at PNNL. This algorithm works in the near-field of both the target and the scanned aperture and preserves the diffraction limited resolution of less than one-wavelength. The wide frequency bandwidth is used to provide depth resolution, which allows the image to be fully focused over a wide range of depths, resulting in a full 3-D image. This is not possible in a normal optical (or quasi-optical) imaging system. This system has been extensively tested using concealed metal and plastic weapons, and has recently been tested using real plastic explosives (C-4 and RDX) and simulated liquid explosives concealed on personnel. Millimeter-waves do not penetrate the human body, so it is necessary to view the subject from several angles in order to fully inspect for concealed weapons. Full animations containing 36 - 72 frames recorded from subjects rotated by 5 - 10 degrees, have been found to be extremely useful for rapid, effective inspection of personnel.

Colt: an experiment in wormhole run-time reconfiguration

Abstract: Wormhole run-time reconfiguration (RTR) is an attempt to create a refined computing paradigm for high performance computational tasks. By combining concepts from field programmable gate array (FPGA) technologies with data flow computing, the Colt/Stallion architecture achieves high utilization of hardware resources, and facilitates rapid run-time reconfiguration. Targeted mainly at DSP-type operations, the Colt integrated circuit -- a prototype wormhole RTR device -- compares favorably to contemporary DSP alternatives in terms of silicon area consumed per unit computation and in computing performance. Although emphasis has been placed on signal processing applications, general purpose computation has not been overlooked. Colt is a prototype that defines an architecture not only at the chip level but also in terms of an overall system design. As this system is realized, the concept of wormhole RTR will be applied to numerical computation and DSP applications including those common to image processing, communications systems, digital filters, acoustic processing, real-time control systems and simulation acceleration.

Stochastic models for haptic texture

Abstract: Recent research in haptic systems has begun to focus on the generation of textures to enhance haptic simulations. Synthetic texture generation can be achieved through the use of stochastic modeling techniques to produce random and pseudo-random texture patterns. These models are based on techniques used in computer graphics texture generation and textured image analysis and modeling. The goal for this project is to synthesize haptic textures that are perceptually distinct. Two new rendering methods for haptic texturing are presented for implementation of stochastic based texture models using a 3 DOF point interaction haptic interface. The synthesized textures can be used in a myriad of applications, including haptic data visualization for blind individuals and overall enhancement of haptic simulations.

Simplified pulse-coupled neural network

Abstract: Recently, the Pulse-Coupled Neural Network (PCNN) was introduced. This network provides a general purpose processor that has the ability to extract edges, segments, and texture from images. These extractions are quite useful for image recognition engines. This paper will introduce a more efficient means of producing results similar to the original PCNN.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Real-time computation of depth from defocus

Abstract: A new range sensing method based on depth from defocus is described. It uses illumination pattern projection to give texture to the object surface. Then the image of the scene is split into two images with different focus settings and sensed simultaneously. The contrast map of the two images are computed and compared pixel by pixel to produce a dense depth map. The illumination pattern and the focus operator to extract the contrast map are designed to achieve finest spatial resolution of the computed depth map and to maximize response of the focus operator. As the algorithm uses only local operations such as convolution and lookup table, the depth map can be computed rapidly on a data-flow image processing hardware. As this projects an illumination pattern and detects the two images with different focus setting from exactly the same direction, it does not share the problem of shadowing and occlusion with triangulation based method and stereo. Its speed and accuracy are demonstrated using a prototype system. The prototype generates 512 by 480 range maps at 30 frame/sec with a depth resolution of 0.3% relative to the object distance. The proposed sensor is composed of off-the-shelf components and outperforms commercial range sensors through its ability to produce complete three-dimensional shape information at video rate.

Periodic broadcasting approach to video-on-demand service

Abstract: The goal of Video-On-Demand (VOD) service is to allow users to access arbitrary video sequences atarbitrary time across wide-area networks. Because of the large amount of data volume associated withreal-time video, the communications and I/O bandwidth requirements pose an extremely difficult thai-lenge to computer systems designers. This paper focuses specifically on the I/O subsystem design for large-scale video servers. We describe a periodic broadcasting approach and its associated data layout al-gorithms to cost-effectively address the I/O bandwidth problems associated with large-scale VOD servers.The paper also presents techniques to support a limited form of VCR-Iike trick plays such as fast forwardand reverse under the proposed framework. Keyword: real-time performance guarantee, video-on-demand servers, periodic broadcasting, fast for-ward and reverse, hierarchical storage systems 1 Introduction Among the interactive multimedia services proposed so far, perhaps the most technologically challenging one is the so-called Video-On-Demand (VOD) service, which allows customers to watch arbitrary video sequences at arbitrary tune

Wavelet-based ground vehicle recognition using acoustic signals

Abstract: We present, in this paper, a wavelet-based acoustic signal analysis to remotely recognize military vehicles using their sound intercepted by acoustic sensors. Since expedited signal recognition is imperative in many military and industrial situations, we developed an algorithm that provides an automated, fast signal recognition once implemented in a real-time hardware system. This algorithm consists of wavelet preprocessing, feature extraction and compact signal representation, and a simple but effective statistical pattern matching. The current status of the algorithm does not require any training. The training is replaced by human selection of reference signals (e.g., squeak or engine exhaust sound) distinctive to each individual vehicle based on human perception. This allows a fast archiving of any new vehicle type in the database once the signal is collected. The wavelet preprocessing provides time-frequency multiresolution analysis using discrete wavelet transform (DWT). Within each resolution level, feature vectors are generated from statistical parameters and energy content of the wavelet coefficients. After applying our algorithm on the intercepted acoustic signals, the resultant feature vectors are compared with the reference vehicle feature vectors in the database using statistical pattern matching to determine the type of vehicle from where the signal originated. Certainly, statistical pattern matching can be replaced by an artificial neural network (ANN); however, the ANN would require training data sets and time to train the net. Unfortunately, this is not always possible for many real world situations, especially collecting data sets from unfriendly ground vehicles to train the ANN. Our methodology using wavelet preprocessing and statistical pattern matching provides robust acoustic signal recognition. We also present an example of vehicle recognition using acoustic signals collected from two different military ground vehicles. In this paper, we will not present the mathematics involved in this research. Instead, the focus of this paper is on the application of various techniques used to achieve our goal of successful recognition.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

320x240 silicon microbolometer uncooled IR FPAs with on-chip offset correction

Abstract: SBRC has developed a high-quality 320 X 240 room- temperature infrared FPA that operates in the 8 - 14 micrometers spectral band. The FPA is based upon the silicon microbolometer technology that has been licensed from Honeywell. This monolithic uncooled FPA utilizes a novel BiCMOS readout circuit that provides high sensitivity and excellent output uniformity. The 320 X 240 FPA operates at frame rates up to 60 Hz with a single output. The microbolometers were fabricated monolithically on the silicon readout circuits at SBRC using VOx as the bolometer material. As advanced microbridge structure design was used that achieves an optical fill-factor greater than 65% in the 48 micrometers X 48 micrometers pixels. The structure also provides excellent thermal isolation for high responsivity and sensitivity. Initial measurements indicate the FPAs are operating with an NETD sensitivity of about 100 mK for an f/1 aperture. This FPA is ultimately expected to operate at sensitivities of less than 20 mK. The FPA also demonstrates peak-to-peak output nonuniformities of less than 100 mV. The FPAs have been mounted in permanently-sealed vacuum packages with single-stage thermoelectric temperature stabilizers. These vacuum packages have been integrated into a camera system that has produced high-quality infrared imagery.

De-noising and contrast enhancement via wavelet shrinkage and nonlinear adaptive gain

Abstract: This paper presents an approach which addresses both de-noising and contrast enhancement. In a multiscale wavelet analysis framework, we take advantage of both soft thresholding and hard thresholding wavelet shrinkage techniques to reduce noise. In addition, we carry out nonlinear processing to enhance contrast within structures and along boundaries. Feature restoration and enhancement are accomplished by modifying the gain of a signal's variational energy. The multiscale discrete dyadic wavelet transform adapted in this paper is treated as a process for the diffusion of variational energy from a signal stored as the power (scaled variational energy) of wavelet coefficients. We show that a discrete dyadic wavelet transform has the capability to separate feature variational energy from noise variational energy. De- noising and feature enhancement are achieved by simultaneously lowering noise variational energy and raising feature variational energy in the transform domain. We present methods for achieving this objective, including regulated soft thresholding and adaptive nonlinear processing combined with hard thresholding. We have applied this algorithm to synthetic and real signals as well as images with additive Gaussian white noise. Experimental results show that de-noised as well as enhanced signals and images are free from artifacts. Sample analysis and experimental results are presented.

Micromachined uncooled VO2-based IR bolometer arrays

Abstract: Bulk silicon micromachined IR bolometer detectors operating at room temperature are presented. These devices are based on VO2 films typically exhibiting a thermal coefficient of resistance of the order of -3%/ degree(s)C. Detector sizes are 50 micrometers X 50 micrometers and 100 micrometers X 100 micrometers , and they are arranged in 1 X 64, 1 X 128 and 1 X 256 pixel linear arrays. A test bench for detector performance evaluation is described. The fabricated detectors exhibit responsivities of up to approximately 20,000 V/W, normalized detectivities typically exceeding 108 cmHz1/2 W-1, and response times typically below 20 ms, At 300 K and a frequency of 30 Hz, the noise equivalent temperature difference for these detectors is of the order of 3 X 10-2 degree(s)C. A bolometer simulation tool is also briefly described.

Text-based search of TV news stories

Abstract: Our goal is to enable viewers to access TV programs based on their content. Towards this end, we present a system that automatically captures and processes TV news programs into a database that can be searched over the internet. Users browse this database by submitting simple English queries. The results of the query is a hyperlinked list of matching news stories. Clicking on any item in the list immediately launches a video of the pertinent part of the news broadcast. We segment TV news broadcasts into distinct news stories. We then index each story as a separate entity. In reply to a query, videos for these news stories are displayed rather than the whole TV program. News program s ar usually accompanied by a transcript in closed caption text. The closed caption text contains markers for story boundaries. Due to the live nature of TV news programs, the closed caption lags the actual audio/video by varying amounts of time up to a few seconds. The closed caption text, thus, has to be shifted to be aligned in time to the video. We use video and audio events to do this synchronization. The closed caption for each story is entered into a database. In response to a query, the database retrieves and ranks the matching closed caption stores. An HTML document is returned to the user which lists: 1) the name and time of the news program that this story belongs to, 2) thumbnails providing a visual summary of the story, 3) closed caption text. To view a news story, the user simply clicks on an item form the list and the video for that story is streamed onto a media player at the user side. This system maintains the manner of presentation of the media, namely video for TV programs, while allowing the common search and selection techniques used on the web.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Speckle noise reduction of airborne SAR images with symmetric Daubechies wavelets

Abstract: We report the study of a multiresolution speckle reduction method for airborne synthetic aperture radar (SAR) images. The SAR image is first subband-coded using complex symmetric Daubechies wavelets, followed by a noise estimate on the three high-pass bands. An elliptic wavelet coefficient thresholding rule is then applied, that preserves the global orientation of the complex wavelet coefficient distribution. FInally, a multiresolution synthesis (inverse wavelet transform) is done in a last small dim objects. A speckle index is computed to quantify the speckle reduction performance. We compare our results with those obtained using median and geometrical (Crimmins) filters.

Microelectro discharge machining as a technology in micromachining

Abstract: In recent years, machine facilities for Electro Discharge Machining (EDM) have been dramatically improved. Enormous progress has been obtained with respect to form accuracy and structure precision even in the submicron domain, which qualifies EDM as a technology for microfabrication ((mu) EDM). (Mu) EDM therefore extends the family of existing microtechniques e.g. the LIGA process or silicon surface micromachining. The EDM-technology offers 3D microfabrication of conductive materials independent of their mechanical properties like hardness, brittleness, etc. This capability offers new fields of application for the microfabrication of components made e.g. from stainless steel or titanium. In order to demonstrate the successful application of various (mu) EDM processes components and devices like micro gearwheels, microreactors, micro punching tools and mould inserts for micro injection molding of an optical fiber connector are presented, which have been fabricated by EDM in close cooperation between the Institute of Microtechnology Mainz GmbH and the Swiss EDM-manufacturer AGIE Losone. Based on their know-how the partners aim to optimize (mu) EDM for microfabrication purposes.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Stick and slip actuators and parallel architectures dedicated to microrobotics

Abstract: Stick and slip actuators are particularly well adapted to microrobotics. A simple design, a very high intrinsic resolution (a few nanometers) and a high rigidity makes them specially interesting for high precision micro manipulations. Moreover, a smart design allows the user to combine the guiding and actuating functions. Parallel architectures are attractive to microrobotics too. They present a high rigidity and the actuators are fixed on the base. This paper deals with the integration of stick and slip actuators in a 6-degrees-of-freedom parallel structure dedicated to the micro assembly of optical components. In section 3 we describe and characterize inertial actuators using the stick and slip effect. We demonstrate their performances (velocity higher than 1.5 mm/s, 10 nm precision) and limits. In section 4 we describe the 6- degrees-of-freedom parallel architecture that we developed for our application and how the actuators are integrated into it. Its kinematics, the joins' forces and the working volume have been calculated. A resolution better than 30 nm is possible within a working volume of 140 mm3. Orientations of several degrees (up to plus or minus five degrees) are possible for the three rotational angles.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Optical and infrared detection using microcantilevers

Abstract: The feasibility of micromechanical optical and infrared (IR) detection using microcantilevers is demonstrated. Microcantilevers provide a simple means for developing single- and multi-element sensors for visible and infrared radiation that are smaller, more sensitive and lower in cost than quantum or thermal detectors. Microcantilevers coated with a heat absorbing layer undergo bending due to the differential stress originating from the bimetallic effect. Bending is proportional to the amount of heat absorbed and can be detected using optical or electrical methods such as resistance changes in piezoresistive cantilevers. The microcantilever sensors exhibit two distinct thermal responses: a fast one ({theta}{sub 1}{sup thermal} < ms) and a slower one ({tau}{sub 2}{sup thermal} {approximately} 10 ms). A noise equivalent temperature difference, NEDT = 90 mK was measured. When uncoated microcantilevers were irradiated by a low-power diode laser ({lambda} = 786 nm) the noise equivalent power, NEP, was found to be 3.5nW/{radical}Hz which corresponds to a specific detectivity, D*, of 3.6 {times} 10{sup 7} cm {center_dot} {radical}Hz/W at a modulation frequency of 20 Hz.

High-resolution infrared image reconstruction using multiple low-resolution aliased frames

Abstract: Staring infrared detectors often produce low resolution images because the technology does not exist to produce higher resolution arrays with sufficient spatial sampling intervals. A proven approach to combat this difficulty involves recording multiple frames that have been optically shifted onto a high-resolution grid pattern and then combined together into a single high resolution image. This process is known as microscanning. In fact, if the infrared (IR) imaging system is mounted on a moving platform, the normal vibrations associated with the platform's movement can be exploited to generate shifts in the acquired images. We present an algorithm that can register this temporal image sequence at the sub-pixel level and then reconstruct a high resolution image from the shifted frames. The proposed algorithm uses a gradient based shift estimator which provides shift information for each of the recorded frames. The reconstruction algorithm is based on a technique of high resolution image reconstruction by solving a series of linear equations in the frequency domain. In this paper, we review the theory behind the registration and reconstruction algorithms and their limitations. We demonstrate that the registration is a viable real-time algorithm that is suitable for applications involving small image shifts (i.e. less than one detector element). We also show that the reconstruction program gives dramatic improvements in the image's resolution and does well in handling the aliased information.

Solving graph problems with dynamic computation structures

Abstract: We introduce dynamic computation structures (DCS), a compilation technique to produce dynamic code for reconfigurable computing. DCS specializes directed graph instances into user-level hardware for reconfigurable architectures. Several problems such as shortest path and transitive closure exhibit the general properties of closed semirings, an algebraic structure for solving directed paths. Motivating our application domain choice of closed semiring problems is the fact that logic emulation software already maps a special case of directed graphs, namely logic netlists, onto arrays of field programmable gate arrays (FPGA). A certain type of logic emulation software called virtual wires further allows an FPGA array to be viewed as a machine-independent computing fabric. Thus, a virtual wires compiler, coupled with front-end commercial behavioral logic synthesis software, enables automatic behavioral compilation into a multi-FPGA computing fabric. We have implemented a DCS front-end compiler to parallelize the entire inner loop of the classic Bellman-Ford algorithm into synthesizable behavioral verilog. Leveraging virtual wire compilation and behavioral synthesis, we have automatically generated designs of 14 to 261 FPGAs from a single graph instance. We achieve speedups proportional to the number of graph edges - - from 10X to almost 400X versus a 125 SPECint SparcStation 10.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Information theoretic approach to sensor scheduling

Abstract: This paper demonstrates an approach to sensor scheduling and sensor management which effectively deals with the search/track decision problem. Every opportunity a sensor has to sense the environment equates to a certain amount of information which can be obtained about the state of the environment. A fundamental question is how to use this potential information to manage a suite of sensors while maximizing one's net knowledge about the state of the environment. The fundamental problem is whether to use one's resources to track targets already in track or to search for new ones. Inherent in this search/track problem is the further decision as to which sensor to use. A computer model has been developed that simulates a modest multiple sensor, multiple threat scenario. Target maneuvers are modeled using the Singer Model for manned maneuvering vehicles. Each sensor's capabilities and characteristics are captured in the model by converting their energy constraints to a probability of detecting a target as a function of range and field of view (beamwidth). The environment is represented by a probability distribution of a target being at a given location. As the environment is sensed and targets are detected, the environment's probability distribution is continually updated to reflect the new probability state of the environment. This probability state represents the system's best estimate about the location of all targets in track and the probable location of, as yet undetected, targets.