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Air Force Institute of Technology

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Articles 2941 - 2970 of 3078

Full-Text Articles in Physical Sciences and Mathematics

Hardware-Verification Through Logic Extraction, Michael A. Dukes Mar 1992

Hardware-Verification Through Logic Extraction, Michael A. Dukes

Theses and Dissertations

A Prolog-based system is described which employs logic-extraction to perform hardware-verification. The extraction rules are built automatically from hierarchical structural VHDL models, enabling the equivalence of a structural VHDL description and a layout specification to be verified. Pin-to-pin critical- path analysis is performed within the logic-extraction process; many noncritical paths are pruned early, making pin-to-pin critical path analysis of large circuits feasible. It is demonstrated that a design methodology based on logic extraction, VHDL, and a layout tool can provide a fabricated functionally- correct IC design without circuit-level or switch-level simulation. This methodology is shown to be practical for VLSI …

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Distributed Ray Casting For High-Speed Volume Rendering, Patricia L. Brightbill Jan 1992

Distributed Ray Casting For High-Speed Volume Rendering, Patricia L. Brightbill

Theses and Dissertations

The volume rendering technique known as ray casting or ray tracing is notoriously slow for large volume sizes, yet provides superior images. A technique is needed to accelerate ray tracing volumes without depending on special purpose or parallel computers. The realization and improvements in distributed computing over the past two decades has motivated its use in this work. This thesis explores a technique to speedup ray casting by distributed programming. The work investigates the possibility of dividing the volume among general purpose workstations and casting rays (using Levoy's front-to-back algorithm) through each subvolume independently. The final step being the composition …

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Migrating A C-Based Cad Tool To An Object-Oriented Database/C++ Environment: Conversion Costs And Performance Analysis, Mark A. Roth, Timothy M. Jacobs Dec 1991

Migrating A C-Based Cad Tool To An Object-Oriented Database/C++ Environment: Conversion Costs And Performance Analysis, Mark A. Roth, Timothy M. Jacobs

AFIT Documents

his paper examines the potential of object-oriented databases to support complex design applications. To do this we migrated the Magic very large scale integrated (VLSI) circuit design tool written in the C language to a new environment in which Magic's existing file management code is replaced with a C++ language interface to the commercial object-oriented database management system (OODBMS) product Object Store. In our initial implementation we found the performance of this tool as implemented on the OODBMS to be marginally faster than the tool as currently implemented with a flat file system in several critical areas. Increased functionality, including …

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Establishing A Methodology For Evaluation And Selecting Computer Aided Software Engineering Tools For A Defined Software Engineering Environment At The Air Force Institute Of Technology School Of Engineering, Jody L. Mattingly Dec 1991

Establishing A Methodology For Evaluation And Selecting Computer Aided Software Engineering Tools For A Defined Software Engineering Environment At The Air Force Institute Of Technology School Of Engineering, Jody L. Mattingly

Theses and Dissertations

This thesis identifies the software engineering environment (SEE) as it exists at the Air Force Institute of Technology (AFIT) School of Engineering. It also describes the software process model employed and the software development methods presented as part of the curriculum. Based on this information, criteria was established to evaluate computer aided software engineering (CASE) tools being considered for integration into the SEE. Each criterion was weighted to indicate its importance when selecting CASE tools. The criteria were further used to establish a methodology to be used to evaluate and select the CASE tools under consideration as well as future …

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Effect Of Spatial Locality Prefetching On Structural Locality, Dirk D. Schalch Dec 1991

Effect Of Spatial Locality Prefetching On Structural Locality, Dirk D. Schalch

Theses and Dissertations

The purpose of this research was to analyze the effect that spatial locality prefetching in cache memory has on the structural locality of program memory referencing behavior. To examine this, a software simulator was built to model a proposed two-level cache memory subsystem. The proposed subsystem was designed to use spatial locality prefetching to exploit the structural locality contained in executing computer workloads. New memory referencing models were developed to incorporate the combined use of structural locality and spatial locality prefetching. From these models, equations were derived to predict the hit rates for both caches. Combined with the state transition …

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Three-Dimensional Medical Image Registration Using A Patient Space Correlation Technique, Patrick J. Rizzuto Jr. Dec 1991

Three-Dimensional Medical Image Registration Using A Patient Space Correlation Technique, Patrick J. Rizzuto Jr.

Theses and Dissertations

The routine clinical use of three-dimensional data provided by modern medical imaging procedures is often impeded by the difficulty in accurately correlating the resultant volume datasets. These data are frequently obtained at different times using the same modality, or images of the same patient are sometimes produced using more than one imaging modality. In order to analyze the similarities and differences between such images, it is necessary for the medical imaging data to be spatially aligned using a process known as image registration. This research investigated a structure-based image registration technique based upon simple, three-dimensional relationships among user identified landmarks. …

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Design Of Style-V — A Translator To Convert Standard Vhdl Into A Stylized Form For Automated Microcode Generation, Dennis A. Rumbley Dec 1991

Design Of Style-V — A Translator To Convert Standard Vhdl Into A Stylized Form For Automated Microcode Generation, Dennis A. Rumbley

Theses and Dissertations

This thesis provides an analysis and preliminary design of Style V, a source-to-source computer language translator. Style-V converts IEEE standard VHDL into a special style of VHDL defined for a commercial tool, the Integrated Design Automation System (IDAS). Thirteen mappings between standard VHDL and the IDAS subset were identified. The mappings were analyzed using Domain Analysis and Modern Structured Analysis techniques. Four processes covering several of the mappings were completely analyzed. One mapping to convert CASE statements to IF statements was implemented. Since the IDAS restricts designs to bit logic, a method for representing multilevel logic with bit logic was …

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A Spatially Partitioned Parallel Simulation Of Colliding Objects, Robert S. Moser Dec 1991

A Spatially Partitioned Parallel Simulation Of Colliding Objects, Robert S. Moser

Theses and Dissertations

This study investigated the application of a conservative synchronization paradigm to the classical, distributed pool balls simulation executed on an eight node, Intel iPSC/2 hypercube. Wieland's concept of spatial partitioning and limited data replication was used. Analysis has shown that 100% parallelization of execution is possible in a conservative environment via assignment of multiple sectors to nodes. Two conservative formulations for minimum safe time were derived. A tradeoff exists between scalability and efficiency. Optimum sectoring prediction has been shown possible through application of linear regression techniques. The results of this research reveal that a conservative approach to distributed, discrete event …

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Improved Task Scheduling For Parallel Simulations, Andrew E. Mcnear Dec 1991

Improved Task Scheduling For Parallel Simulations, Andrew E. Mcnear

Theses and Dissertations

The objective of this investigation is to design, analyze, and validate the generation of optimal schedules for simulation systems. Improved performance in simulation execution times can greatly improve the return rate of information provided by such simulations resulting in reduced development costs of future computer/electronic systems. Optimal schedule generation of precedence-constrained task systems including iterative feedback systems such as VHDL or war gaming simulations for execution on a parallel computer is known to be N P-hard. Efficiently parallelizing such problems takes full advantage of present computer technology to achieve a significant reduction in the search times required. Unfortunately, the extreme …

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An Application Of The Object-Oriented Paradigm To A Flight Simulator, Dennis J. Simpson Dec 1991

An Application Of The Object-Oriented Paradigm To A Flight Simulator, Dennis J. Simpson

Theses and Dissertations

This thesis describes the object-oriented software development techniques that were used to analyze, design and implement a flight simulator. The objective of this thesis was to present a comprehensive object-oriented software development methodology and show how it was used in constructing an actual application. An extensive review of current object-oriented practices is presented along with the methods that were used to take the flight simulator from analysis to design and through to implementation. The description of the methodology concentrates upon the design and implementation phases of the object-oriented software lifecycle. Examples from the design of the flight simulator demonstrate how …

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A Hybrid Approach To Battlefield Parallel Discrete Event Simulation, Steven R. Soderholm Dec 1991

A Hybrid Approach To Battlefield Parallel Discrete Event Simulation, Steven R. Soderholm

Theses and Dissertations

This thesis describes a method of parallelizing a battlefield discrete event simulation. The method combines elements of conservative time synchronization together with elements of optimistic computation and local rollback on a message passing hardware architecture. The battle simulation features aircraft moving in a battle area and launching missiles at enemy aircraft. Aircraft are randomly grouped into logical process (LPs), and a single LP is assigned to each processor. Aircraft state information is replicated across all LPs. Only the LP with the minimum next event time can execute safely. While one LP is executing safely all other LPs are precomputing their …

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A Cache Design To Exploit Structural Locality, Curtis M. Winstead Dec 1991

A Cache Design To Exploit Structural Locality, Curtis M. Winstead

Theses and Dissertations

A design and VHDL implementation of a content-addressable memory (CAM) to exploit structural locality is the subject of this research. The concept of structural locality is that memory locations are referenced in the same order as they were previously referenced. Therefore, if memory locations that exhibit structural locality can be made available to the CPU (Center Processing Unit) through a fast data store, an increase in speed of the computer system can be realized. The CAM's purpose is to store memory references in the order they were used by the CPU and prefetch these locations to a smaller on- chip …

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Parallelizing Serial Code For A Distributed Processing Environment With An Application To High Frequency Electromagnetic Scattering, Paul R. Work Dec 1991

Parallelizing Serial Code For A Distributed Processing Environment With An Application To High Frequency Electromagnetic Scattering, Paul R. Work

Theses and Dissertations

This thesis investigates the parallelization of existing serial programs in computational electromagnetics for use in a parallel environment. Existing Algorithms for calculating the radar cross section of a object are covered, and a ray-tracing code is chosen for implementation on a parallel machine. Current parallel architectures are introduced and a suitable parallel machine is selected for the implementation of the chosen ray tracing algorithm. The standard techniques for the parallelization of serial code are discussed, including load balancing and decomposition considerations, and appropriate methods for the parallelization effort are selected. A load balancing algorithm is modified to increase the efficiency …

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Formalization And Validation Of An Sadt Specification Through Executable Simulation In Vhdl, Daniel L. Eickmeier Dec 1991

Formalization And Validation Of An Sadt Specification Through Executable Simulation In Vhdl, Daniel L. Eickmeier

Theses and Dissertations

Formalizing an informal requirements specification, such as SADT, and executing the formal specification in a simulation environment, such as VHDL, provides a requirements analyst a means to validate the behavior of a specification early in the development life cycle. This research effort investigated and demonstrated the feasibility and benefit of transforming an SADT specification of a system into an equivalent VHDL executable simulation. Both non-time related behavior and concurrent, real-time related behavior is addressed. First, a decision table extension to SADT is created so that detailed, executable behavior can be specified. Next a mapping from SADT to VHDL is defined. …

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Lqg Control Of A Deformable Mirror Adaptive Optics System With Time- Delayed Measurements, David J. Anderson Dec 1991

Lqg Control Of A Deformable Mirror Adaptive Optics System With Time- Delayed Measurements, David J. Anderson

Theses and Dissertations

This thesis proposes a linear quadratic Gaussian (LQG) control law for a ground-based deformable mirror adaptive optics system. The incoming image wavefront is distorted, primarily in phase, due to the turbulent effects of the earth's atmosphere. The adaptive optics system attempts to compensate for the distortion with a deformable mirror. A Hartman wavefront sensor measures the degree of distortion in the image wavefront. The measurements are input to a Kalman filter which estimates the system states. The state estimates are processed by a linear quadratic regulator which generates the appropriate control voltages to apply to the deformable mirror actuators. The …

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Robotic Tactile Sensors Fabricated From A Monolithic Silicon Integrated Circuit And A Piezoelectric Polyvinylidene Fluoride Thin Film, Craig S. Dyson Dec 1991

Robotic Tactile Sensors Fabricated From A Monolithic Silicon Integrated Circuit And A Piezoelectric Polyvinylidene Fluoride Thin Film, Craig S. Dyson

Theses and Dissertations

The purpose of this research effort was to design, fabricate, and test a tactile sensor system consisting of an external high impedance switch circuit, an external multiplexing circuit, and a tactile sensor IC. In order to accomplish this objective, a hardware design and selection process was implemented along with a logical test methodology. An external multiplexer circuit samples all of the array elements in 50 ms. The current prototype sensor has linearity spanning loads of 0.8 g to 135 g, a load resolution of 20 g, and a maximum bandwidth of 25 Hz. Using an elementary shape recognition algorithm the …

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A Rigorous Uniform Diffraction Analysis Of The Electromagnetic Scattering From Impedance Edges And Junctions, Joseph C. Fortney Dec 1991

A Rigorous Uniform Diffraction Analysis Of The Electromagnetic Scattering From Impedance Edges And Junctions, Joseph C. Fortney

Theses and Dissertations

This paper investigates the scattering from impedance strips and impedance-loaded conducting strips. The impedance strips are analyzed using Senior's impedance half plane formulation. Once the primary diffraction from the impedance half plane is presented, it is used to develop multiple diffraction mechanisms on an impedance strip. The scattering from impedance-loaded strips are analyzed using Maliuzhinets' impedance wedge formulation. The primary diffraction mechanism from an impedance wedge is used to develop the multiple diffractions on an impedance double wedge. The multiple diffractions on both types of strips are developed using the Extended Spectral Ray Method. Sample calculations are made for impedance …

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Control Of A Large Flexible Space Structure Using Multiple Model Adaptive Algorithms, John A. Gustafson Dec 1991

Control Of A Large Flexible Space Structure Using Multiple Model Adaptive Algorithms, John A. Gustafson

Theses and Dissertations

The development and performance of moving-bank multiple model adaptive estimation (MMAE) and control (MMAC) algorithms for quelling vibrations induced in the SPICE 2 space structure are analyzed in this thesis. The structure consists of a large platform and a smaller platform connected by three legs in a tripod fashion. The model supplied by Phillips Laboratory, Kirtland AFB is used to develop a truth model and multiple reduced ordered filter models. The filter models are developed from modal analysis and internally balanced techniques. Deviations of the line-of-sight vector from the center of the large platform to the center of the smaller …

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Design And Testing Of A Lightweight, Planar Microwave Lens, Paul M. Proudfoot Dec 1991

Design And Testing Of A Lightweight, Planar Microwave Lens, Paul M. Proudfoot

Theses and Dissertations

This thesis documents the design, fabrication, and testing of a lightweight, planar microwave lens. The lens consists of two planar arrays of lightweight printed circuit antennas interconnected by microstrip lines whose length varies as a function of position on the lens. Microwave energy is coupled from one face of the lens to the other by means of a slot etched in the ground plane. At 8.0 GHz the lens is ten wavelengths across, is less than 1/8 inch thick, and weighs less than 4 pounds. The lens can scan a beam over a ± 30 degree region in both the …

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Design Of A Fiber Optic Image Transmission Link, Justin D. Redd Dec 1991

Design Of A Fiber Optic Image Transmission Link, Justin D. Redd

Theses and Dissertations

An original design is presented for a fiber optic based digital image transmission link operating at a serial bit rate of 250 Mbits/Second. The link is designed as an integral part of an airborne infrared imaging system with particular emphasis on avoiding problems associated with aircraft electromagnetic interference (EMI). Unique features include simplicity (single PC board transmitter and receiver), low power, low cost (under $3,000), and use of the latest off-the-shelf components (including the Gazelle GA9011/GA9012 HOT ROD chip set). Theoretical modeling is used to predict a bit error rate of better than 10-15, while actual measurements include …

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Sensing Refractive Turbulence Profiles Using Wave Front Slope Measurements From Two Reference Sources, Michael D. Rejack Dec 1991

Sensing Refractive Turbulence Profiles Using Wave Front Slope Measurements From Two Reference Sources, Michael D. Rejack

Theses and Dissertations

This thesis examines a remote sensing technique for measuring the atmospheric structure constant as a function of altitude by performing spatial correlation or wavefront sensor measurements. Two point sources are used to irradiate two wavefront sensors in the aperture plane of an optical system. The geometric relationship between the sources and the sensors gives rise to crossed optical paths. At the point where the paths cross, the correlation value of the turbulence contributions will be at a peak. The correlation is shown to be mathematically related to the structure constant in terms of an integral of the structure constant multiplied …

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Image Segmentation Using Affine Wavelets, Steven E. Smiley Dec 1991

Image Segmentation Using Affine Wavelets, Steven E. Smiley

Theses and Dissertations

This thesis discusses the use of the multiresolution representation and Radial Basis Function (RBF) neural networks to segment both FLIR and SAR imagery. The multiresolution approximation coefficients are used as features into the RBF network which learns to distinguish between different cultural and natural regions or objects. The wavelets used are Mallat's spline wavelet and Daubechies' compactly supported wavelets. Additionally, this thesis provides an explanation of wavelets in a tutorial manner. It introduces wavelet theory and discusses two different approaches to generating the multiresolution or wavelet representation.

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Face Recognition With The Karhunen-Loeve Transform, Pedro F. Suarez Dec 1991

Face Recognition With The Karhunen-Loeve Transform, Pedro F. Suarez

Theses and Dissertations

The major goal of this research was to investigate machine recognition of faces. The approach taken to achieve this goal was to investigate the use of Karhunen-Loe've Transform (KLT) by implementing flexible and practical code. The KLT utilizes the eigenvectors of the covariance matrix as a basis set. Faces were projected onto the eigenvectors, called eigenfaces, and the resulting projection coefficients were used as features. Face recognition accuracies for the KLT coefficients were superior to Fourier based techniques. Additionally, this thesis demonstrated the image compression and reconstruction capabilities of the KLT. This theses also developed the use of the KLT …

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Real Imagery As A Three Dimensional Display, Juan C. Echeverry Dec 1991

Real Imagery As A Three Dimensional Display, Juan C. Echeverry

Theses and Dissertations

This research effort implemented two 3-D display designs to assess their performance and effect on an observer's depth perception. Both 3-D displays produced real images for the observer to view. The first display setup combined a lens relay with a two concave mirror projector. The second display setup combined the two concave mirror projector with a diffuser. The lens relay/ two concave mirror projector combination was successful in imaging a source from the CRT to a point in space above the two mirror system. The problem was that the observer could not assess the image location by just looking at …

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An Investigation Of The Application Of Artificial Neural Networks To Adaptive Optics Imaging Systems, Andrew H. Suzuki Dec 1991

An Investigation Of The Application Of Artificial Neural Networks To Adaptive Optics Imaging Systems, Andrew H. Suzuki

Theses and Dissertations

Recurrent and feedforward artificial neural networks are developed as wavefront reconstructors. The recurrent neural network studied is the Hopfield neural network and the feedforward neural network studied is the single layer perceptron artificial neural network. The recurrent artificial neural network input features are the wavefront sensor slope outputs and neighboring actuator feedback commands. The feedforward artificial neural network input features are just the wavefront sensor slope outputs. Both artificial neural networks use their inputs to calculate deformable mirror actuator commands. The effects of training are examined.

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Performance Analysis Of The Speckle Holography Image Reconstruction Technique, Rudolf N. Vonniederhausern Dec 1991

Performance Analysis Of The Speckle Holography Image Reconstruction Technique, Rudolf N. Vonniederhausern

Theses and Dissertations

In speckle holography, short exposures frames along with wave front measurements allow post processing image reconstruction. With speckle holography the amplitude of high spatial frequencies is boosted to allow resolution out to the diffraction limit of the telescope. To provide system parameters for the wave front sensor design, a software analysis program has been developed that provides the system transfer function as a function of the number and size of sensor subapertures and sensor noise. Trends in the ratio of the atmospheric coherence diameter to wave front subaperture size and the effect on the system transfer function have been obtained. …

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Optical Image Segmentation Using Wavelet Correlation, Steven D. Pinski Dec 1991

Optical Image Segmentation Using Wavelet Correlation, Steven D. Pinski

Theses and Dissertations

This research introduces an optical method of segmenting potential targets using wavelet analysis. Implementation of an optical Harr wavelet is fulfilled using a magneto-optic spatial light modulator (MOSLM). Two methods of controlling wavelet dilation are explored: (1) spatial filtering of a ternary modulated MOSLM; (2) a single aperture positioned in front of a binary modulated MOSLM. Segmentation is performed through Vander Lugt correlation of a binarized image with a binarized optical wavelet. Three different image binarization methods are investigated for use in the correlation scheme: (1) average pixel value over an entire scene; (2) localized 4 x 4 pixel average …

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Low Temperature Photoluminescence Study Of Silicon-Germanium Alloy Superlattices, Maxwell M. Chi Dec 1991

Low Temperature Photoluminescence Study Of Silicon-Germanium Alloy Superlattices, Maxwell M. Chi

Theses and Dissertations

Low temperature photoluminescence studies were performed on nine silicon germanium alloy superlattice samples. The luminescence spectra showed sharp peaks in the 0.95 to 1.05 eV energy range, and a broad band located 0.05 to 0.12 eV below the alloy bandgap. The sharp peaks were identified as transitions associated with impurity bound excitons. The linewidth was about 10 times that in pure silicon; in addition, the peaks shifted to lower energy as the sample temperature was raised from 1.4 to 15 K. These features were attributed to effects of random distribution of atoms in the alloy. The broad band shifted to …

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An Analysis Of One-Dimensional Models Of The Insulating And Conducting Priz, Joseph W. Cook Iii Dec 1991

An Analysis Of One-Dimensional Models Of The Insulating And Conducting Priz, Joseph W. Cook Iii

Theses and Dissertations

This study attempted to analytically reproduce experimental and analytical data, on the single-insulated and conducting PRIZ, presented in 1987 and 1988 by the Soviet scientists Bliznetsov et al. Our onedimensional analytical models, derived from earlier Soviet reports, have consistently reproduced previously reported data on the PRIZ. In this study, the same codes were successfully used to analyze the effects of injection at high and low intensity exposures (30 µW/cm2 to 500 mW/cm2) Although the codes qualitatively duplicated the nature of the space charge distribution in the single-insulated and conducting PRIZ, our quantitative results were significantly different from …

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Self-Pumped Phase-Conjugate Twyman-Green Interferometry Using A Batio3 Crystal, Deborah A. Determan Dec 1991

Self-Pumped Phase-Conjugate Twyman-Green Interferometry Using A Batio3 Crystal, Deborah A. Determan

Theses and Dissertations

The Air Force uses optical imaging systems in many fields such as communications, target recognition, and missile guidance. For proper execution of these applications, the optical imaging systems use in these fields must be of extremely high quality so that an ideal image is obtained. In divergent beam configurations, this type of interferometer would eliminate the need for high quality reference optics needed in conventional Twyman-Green interferometry. The objective of this thesis is to demonstrate phase conjugate Twyman-Green interferometry using a barium titanate (BaTiO3) crystal as the phase conjugating mirror in the reference arm of the interferometer and …

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