In this paper, Bayesian inference is applied to performance metrics definition of the important class of recent Homeland
Security and defense systems called binary sensors, including both (internal) system performance and (external)
CONOPS. The medical analogy is used to define the PPV (Positive Predictive Value), the basic Bayesian metrics
parameter of the binary sensors. Also, Small System Integration (SSI) is discussed in the context of recent Homeland
Security and defense applications, emphasizing a highly multi-technological approach, within the broad range of clusters
("nexus") of electronics, optics, X-ray physics, γ-ray physics, and other disciplines.
In this paper, biologically-inspired optical imaging systems, including fish eye, bug eye, lobster eye, and RGB color
vision, are discussed as new lensing systems for military and homeland security applications. This new area of interest
includes UV, VIS, IR, and X-ray part of electromagnetic spectrum. In particular, recent progress at Physical Optics
Corporation will be discussed, including such applications as hyperspectral/multi-spectral imagery, video surveillance,
and X-ray inspection.
KEYWORDS: Homeland security, Modeling and simulation, Prototyping, 3D modeling, Systems modeling, System integration, Microwave radiation, Systems engineering, X-ray optics, Manufacturing
A highly productive approach to small systems design and integration (SSDI), and modeling and simulation (M&S),
based on rapid/interactive prototyping has been effectively used at Physical Optics Corporation (POC) to support small
system development of "intellectual products" that cover a broad range of electromagnetic spectra (X-ray, optical,
infrared, and microwave). In particular, the implementation of an accelerated interactive modeling (AIM) environment
produces effective engineering solutions for tackling difficult and complex technical issues for combining 3D
mechanical design and microwave engineering. In addition, using established small systems engineering principles and
the effective use of collaborative input at the start of a development effort that incorporates a diverse range of areas like
optics, mechanics, electronics, software, thermal modeling, electromagnetism, surface chemistry, and manufacturing
plays an important role in the success of future military and homeland security applications.
Non-invasive real-time detection and identification of high explosives and improvised explosive devices, illicit materials
hidden inside suitcases, vehicles, containers or behind metal and non-metal walls become critically important for safety
and security worldwide. In this paper we will discuss non-scanning, portable real-time detection X-ray backscattering
system based on novel Lobster-Eye X-ray focusing optics, which focuses backscatter photons from fully obscured objects
several meters away that are being irradiated by short high-power X-ray pulses. Due to the ability of Lobster-Eye lenses to
focus X-rays, such imaging systems collect more photons into a smaller spot, compared to traditional pinhole systems. This
results in a higher signal-to-noise ratio and better spatial resolution. The signal-to-noise ratio can be further improved by
using pulsed X-ray irradiation and a gated X-ray camera. The images can be further improved by software processing,
which allows to reconstruct the object with high accuracy adequate for detection with high probability and low false alarm
rate.
An inexpensive, easily integrated, sensitive photoreceiver operating in the communications band with a 50-GHz
bandwidth would revolutionize the free-space communication industry. While generation of 50-GHz carrier AM or FM
signals is not difficult, its reception and heterodyning require specific, known technologies, generally based on silicon
semiconductors. We present a 50 GHz photoreceiver that exceeds the capabilities of current devices. The proposed
photoreceiver is based on a technology we call Nanodust. This new technology enables nano-optical photodetectors to
be directly embedded in silicon matrices, or into CMOS reception/heterodyning circuits. Photoreceivers based on
Nanodust technology can be designed to operate in any spectral region, the most important to date being the
telecommunications band near 1.55 micrometers. Unlike current photodetectors that operate in this spectral region,
Nanodust photodetectors can be directly integrated with standard CMOS and silicon-based circuitry. Nanodust
technology lends itself well to normal-incidence signal reception, significantly increasing the reception area without
compromising the bandwidth. Preliminary experiments have demonstrated a free-space responsivity of 50 &mgr;A/(W/cm2),
nearly an order of magnitude greater than that offered by current 50-GHz detectors. We expect to increase the Nanodust
responsivity significantly in upcoming experiments.
The angular distribution of the inelastic scattering of photons at low energies (≤80 KeV) has been measured in organic material, soil, rocks, wood, steel sheet, and water. The measurements have been performed under air inside an X-ray shield cabinet using X-rays tube as a photon source and a thermoelectrically cooled CdTe detector. Measurements have been taken for both single and combined materials. The contributions of inelastic scattering of photons for the lower Z material in a given configuration have been extracted. The measured signal is primarily Compton scattering. The measured inelastic scattering contributions were compared with the calculated inelastic scattering cross sections according to the Klein-Nishina theory, updated to include a practical energy distribution of an X-ray tube beam. Relatively good agreement was found for all targets under investigation. The slight discrepancy is attributed to photoelectric effect and sample configuration. Present results may act as a guide for optimization of X-ray imaging sensors and in particular of those based on lobster eye X-ray optics suitable for cargo inspection, improvised explosives detection, non-destructive evaluation, and medical imaging.
A new approach to hard X-ray imaging is proposed, based on staring optics consisting of a lobster-eye lens. This new Staring Imaging Lobster-Eye X-Ray approach is especially suited to X-ray lobster-eye imaging of non-astronomical objects at finite distances, because the staring optics replacing the standard scanning optics, result in an extremely efficient power budget, making possible not only the use of low-efficiency Compton backscattering but also operation with low-flux X-ray beams, increasing operator safety. The lobster-eye optics, consisting of square-cross-section microchannels, transmit an X-ray beam by total external reflection. This mode of operation has already been verified for viewing astronomical objects. Its major challenge is minimizing image defocusing by apodization. For this purpose, a new lens imaging equation is derived, and a new local optical axis concept is defined. Applications include medical imaging, cargo inspection, non-destructive testing, industrial and security safeguards, and surveillance.
Advances in the development of imaging sensors depend upon (among other things) the testing capabilities of research laboratories. Sensors and sensor suites need to be rigorously tested under laboratory and field conditions before being put to use. Real-time dynamic simulation of real targets is a key component of such testing, as actual full-scale tests with real targets are extremely expensive and time consuming and are not suitable for early stages of development. Dynamic projectors simulate tactical images and scenes. Several technologies exist for projecting IR and visible scenes to simulate tactical battlefield patterns - large format resistor arrays, liquid crystal light valves, Eidophor type projecting systems, and micromirror arrays, for example. These technologies are slow, or are restricted either in the modulator array size or in spectral bandwidth. In addition, many operate only in specific bandwidth regions. Physical Optics Corporation is developing an alternative to current scene projectors. This projector is designed to operate over the visible, near-IR, MWIR, and LWIR spectra simultaneously, from 300 nm to 20 μm. The resolution is 2 megapixels, and the designed frame rate is 120 Hz (40 Hz in color). To ensure high-resolution visible imagery and pixel-to-pixel apparent temperature difference of 100°C, the contrast between adjacent pixels is >100:1 in the visible to near-IR, MWIR, and LWIR. This scene projector is designed to produce a flickerless analog signal, suitable for staring and scanning arrays, and to be capable of operation in a hardware-in-the-loop test system. Tests performed on an initial prototype demonstrated contrast of 250:1 in the visible with non-optimized hardware.
KEYWORDS: Video, Image compression, Video compression, Video surveillance, System integration, Sensors, Electronics, Mechanics, Connectors, Telecommunications
In this paper, we discuss two important topics: the first one, soft computing, is directly related to the digital image processing, while the second one, Small Systems Integration (SSI), is a broad-range extension of the first one, dealing with such interdisciplinary subjects, as optics, electronics, mechanics, materials, and heat management.
Bidirectional (mutual) injection locking was demonstrated with solid-state lasers, producing significant improvements over traditional single-direction injection locking. Each laser element shares part of its output with other elements in bidirectional locking, distinct from single-direction (traditional) injection locking where one master laser provides the locking signal for a number of slaves. In a phase-locked array, the individual laser outputs add coherently, and the brightness of the entire array scales with the square of the number of elements, as if the active material diameter were increasing. Benefits of bidirectional locking, when compared to traditional injection locking, include reduced laser threshold, better output beam quality, and improved scaling capability. Experiments using two Nd:YVO4 lasers confirmed that mutual injection locking reduced lasing threshold by a factor of at least two and increased the output beam quality significantly. The injection locking effects began with 0.03% coupling between lasers and full-phase locking for coupling exceeding 0.5%. The 0.5% requirement for full phase-locking limits traditional injection-locked arrays to fewer than 100 elements, while mutually injection-locked arrays have no such limit. Mutual injection locking of an array of lasers can lead to a new architecture for high-power laser systems.
Conventional nondestructive evaluation (NDE) techniques include visual inspection, eddy current scanning, ultrasonics, and fluorescent dye penetration. These techniques are limited to local evaluation, often miss small buried defects, and are useful only on polished surfaces. Advanced NDE techniques include laser ultrasonics, holographic interferometry, structural integrity monitoring, shearography, and thermography. A variation of shearography, employing reflective shearographic interferometry, has been developed. This new shearographic interferometer is discussed, together with models to optimize its performance and experiments demonstrating its use in NDE.
The most accurate method of measuring distance and motion is interferometry. This method of motion measurement correlates change in distance to change in phase of an optical signal. As one mirror in the interferometer moves, the resulting phase variation is visualized as motion of interferometric fringes. While traditional optical interferometry can easily be used to measure distance variation as small as 10 nm, it is not a viable method for measuring distance to, or motion of, an object located at a distance grater than half the coherence length of the illumination source. This typically limits interferometry to measurements of objects within <1 km of the interferometer. We present a new interferometer based on phase conjugation, which greatly increases the maximum distance between the illumination laser and the movable target. This method is as accurate as traditional interferometry, but is less sensitive to laser pointing error and operates over a longer path. Experiments demonstrated measurement accuracy of <15 nm with a laser-target separation of 50 times the laser coherence length.
This paper presents feasibility studies of a multispectral moving target detection (MTD) system designed to detect and track low-signature moving targets. The system performs multispectral detection based on linear and nonlinear optimal discriminating features (ODF) for low-signature target detection and correlation tracking of slowly moving targets in clutter. Multispectral detection was tested against multispectral data from an acousto-optic tunable filter in the visible and near infrared. Optical Joint Transform Correlator for target tracking was designed and manufactured. The feasibility of correlation target tracking was demonstrated with actual Army MICOM FLIR long wavelength infrared (LWIR: 8 to 12 μm) images of moving vehicles and tanks in clutter.
In response to a pressing demand for tagging systems and technologies developing, Physical Optics Corporation (POC) proposes a novel Passive Optoelectronical (POET) Tag system. The POET tag is an omnidirectional (360° in azimuth), with up to 180° field-of-view in elevation, retroreflection optical system with a high frequency multiple quantum well (MQW) light intensity modulator for free space IR optical communication. The POET tag optical scheme is a compact, high quality generalized fish-eye lens with telecentric arrangement in image space. The telecentric arrangement in image space provides perfect omnidirectional retroreflection of a recall beam and an optimum divergent of light at the MQW providing maximum modulation contrast ratios. The important POET tag features are low power consumption, zero probability of jamming and intercepting (high security of communication,) because it operates in a passive retroreflection mode with a highly-directed optical beam.
Embedded training is to enhance and maintain the skill proficiency of fleet/armor personnel in taking advantage of the capabilities built into or added onto operational systems, subsystems, or equipment. Physical Optics Corporation (POC) is developing a new scene projector system (collimating display system for out-the window) for simulation applications, where it can fully be integrated into tanks, automobiles, submarines, and other vehicles. This concept integrates the advanced holographic technology with Beowulf computer-cluster highly parallel microprocessors.
KEYWORDS: 3D displays, Holography, 3D image processing, Eye, Diffusers, Commercial off the shelf technology, 3D applications, Holographic optical elements, LCDs, Goggles
We propose a novel true 3-D display based on holographic optics, called HAD (Holographic Autostereoscopic Display), or Holographic Inverse Look-around and Autostereoscopic Reality (HILAR), its latest generation. It does not require goggles, unlike the state of the art 3-D system which do not work without goggles, and has a table-like 360° look-around capability. Also, novel 3-D image-rendering software, based on Beowulf PC cluster hardware is discussed.
This paper presents feasibility studies of a multispectral moving target detection (MTD) system designed to detect and track low-signature moving targets. The system performs multispectral detection based on linear and nonlinear maximum discrimination and representation features (MRDF) for low-signature target detection and correlation tracking of slowly moving targets in clutter. Multispectral detection was tested against multispectral data from an acousto-optic tunable filter in the visible and near IR. The feasibility of correlation target tracking was demonstrated with actual Army MICOM FLIR long wavelength IR images of moving vehicles and tanks in clutter.
KEYWORDS: LCDs, Video, Light emitting diodes, LED backlight, Commercial off the shelf technology, Video compression, Electronics, Diffusers, Wireless communications, Reflectors
KEYWORDS: LIDAR, 3D displays, 3D image processing, Visualization, Optical sensors, Environmental sensing, 3D visualizations, Profilometers, Sensors, 3D vision
In this paper, LIDAR imaging sensors, 3D synthetic and natural object-centric environment, and temporal ATR are discussed in the context of Modeling and Simulation and Hardware-in-the-loop testing.
New approaches to light directionality and backlighting are described. They are discussed in the general context of the Liouville theorem and the second principle of thermodynamics; 3-D autostereoscopic applications are also discussed.
This paper describes the development of real-time non-contact metrology based on holographic interferometry and neural network fringe analysis software to detect defects in composite materials. The object under inspection is illuminated by a high-power solid-state laser, and the light scattered from the material surface is recorded in real time using a double-exposure holographic interferometer, which can detect minute surface deformation caused by defects in the material. Thermal stimulation of the object creates a non- uniform time-varying material reaction, which causes surface deformation that is characteristic of the material's internal structure. This deformation in turn creates time-varying interference patterns, which are recorded by a real-time holographic interferometric system and displayed on the computer monitor through a CCD camera. The system allows real- time, in-depth non-contact inspection of composite materials used in aircraft and other military vehicles. A genetic algorithm has also been developed for fast data processing in a non-laboratory environment. The sophisticated neural network recognizes the types of defects at high speed.
KEYWORDS: Liquid crystals, 3D displays, Diffusers, Holography, LCDs, Diffusion, 3D volumetric displays, 3D image processing, Spatial light modulators, Projection systems
Volumetric 3-D displays proposed and demonstrated in the past have been low in resolution and refresh rate, but not in cost. This paper describes the development of an electro-optic multiplanar volumetric 3-D display (without moving parts) based on unique liquid crystal (LC) switchable light diffusion panels. These LC switchable diffuser panels are produced by our proprietary holographic Light Shaping Diffuser fabrication process. Using a stack of closely spaced LC switchable diffusers, which have shown excellent switching speed, diffusion efficiency, and clarity, a multiplanar volumetric 3- D display was demonstrated, projecting full-color 2-D images from a high speed spatial light modulator.
This paper describes the STAR architecture that is being developed at Physical Optics Corporation for military and commercial use. Because the STAR architecture is based on non- imaging optics, lightpipes, and diffusers, these component technologies are described in detail. Major emphasis in this paper is on the light shaping diffuser, which functions as a non-Lambertian controlled scatterer. This diffuser is becoming a critical element of a number of military and commercial displays, and therefore we have taken the liberty to describe it in detail so that scientists and engineers can optimize their current displays in terms of brightness, uniformity, homogeneity, compactness, and ease of operation.
KEYWORDS: Holography, 3D displays, LCDs, Projection systems, Multiplexing, 3D image processing, Holograms, Video, 3D volumetric displays, Holographic optical elements
Various 3-D display technologies have been proposed for future cockpit displays, all with limitations. This paper describes a 3-D display technology based on a unique multiplexed holographic projection screen developed at Physical Optics Corporation. Making use of multiplexed holographic projection of multiperspective images, this display allows 360 degree look-around viewing of volume-like 3-D images by many viewers without any eyewear. By means of a high-resolution, high-speed 2-D light modulator such as an LCD or Digital Micromirror Device, the display can produce real-time full-color, high resolution 3-D images.
The Super-Anamorphic Backlighting Remote Imaging Display (SABRID) collimating system is the purpose of this paper. The SABRID transforms point light source into collimated (plane) beam. In contrast to common bulky axial-symmetry lens collimator, the highly compact SABRID has three (3) axes of symmetry. The SABRID is attractive for many civilian and military applications, when compactness and/or separation of source light power (up to 20 m) from display itself is essential for safety packaging and other purposes.
Traditional methods of marking aircraft landing zones during combat deployment operations range from simple reflective panels and colored smoke to the more elaborate strobe lighting systems and active radio frequency transceivers. Downed pilots, pathfinders, and special operations personnel are in jeopardy of detection by unfriendly ground forces, active location/direction devices act as beacons to foes as well as friends. Even passive devices can have unacceptable detection profiles. A highly directional fiber optic-based miniaturized landing director minimizes the more undesirable consequences of high profile directional devices.
This paper describes the development of a non-contact diagnosis system for analyzing the plasma density profile, temperature profile, and ionic species of a high energy laser-generated plasma. The system was developed by Physical Optics Corporation in cooperation with the U.S. Army Space and Missile Defense Command, High Energy Laser Systems Test Facility at White Sands Missile Range, New Mexico. The non- contact diagnostic system consists of three subsystems: an optical fiber-based interferometer, a plasma spectrometer, and a genetic algorithm-based fringe-image processor. In the interferometer subsystem, the transmitter and the receiver are each packaged as a compact module. A narrow notch filter rejects strong plasma light, passing only the laser probing beam, which carries the plasma density information. The plasma spectrum signal is collected by an optical fiber head, which is connected to a compact spectrometer. Real- time genetic algorithm-based data processing/display permits instantaneous analysis of the plasma characteristics. The research effort included design and fabrication of a vacuum chamber, and high-energy laser plasma generation. Compactness, real-time operation, and ease of use make the laser plasma diagnosis system well suited for dual use applications such as diagnosis of electric arc and other industrial plasmas.
This paper describes an Opto-Silicon Adaptive Imaging (OSAI) system capable of operating at low light intensities with high resolution, high accuracy, wide dynamic range, and high speed. The system consists of three major subsystems: (1) an adaptive imaging system in which a liquid crystal wavefront corrector measures image quality based on statistical analysis of a speckle field; (2) an image quality analyzer (IQA); (3) an opto-silicon multi-chip module combining a high-resolution ferroelectric liquid crystal SLM, CCD photodetector array, field-programmable gate array, and digital signal processor. The OSAI wavefront control applies adaptive optoelectronic feedback for iterative wavefront restoration and distortion compensation, suing an image quality metric based on statistical properties of the speckle field produced by moving a diffuser in the Fourier transform plane of a IQA optical system. A prototype IQA system was designed, manufactured, and tested using an input liquid crystal SLM, a Fourier lens, a light-shaping diffuser, and an output photodiode.
This paper describes all-optical packet header processing by content-addressable memory and optical joint transform correlation. The results of proof-of-principle computer simulation and experiment are presented.
This work addresses the problem faced by an aircraft that is off its nominal flight path. The goal is to find the optimal trajectory to safely and efficiently return the aircraft to its proper path in rugged terrain. The authors approach to this problem is to consider the space of possible trajectories as a series of linked maneuvers, so that a particular trajectory can be described by the ordered list of parameters specifying the maneuvers. A penalty function is minimized with respect to variations of the maneuver parameter list. The work considered trajectories of up to three straight flight segments linked by turns. The penalty function includes terms penalizing elapsed time for the measure, distance climbed, and closest approach to the ground as well as distance from the nominal flight path at the end of the maneuver. Minimization is performed by means of an adaptive fuzzy-logic-enhanced genetic algorithm.
Head- and helmet-mounted displays can benefit greatly from new image generating technologies. This paper describes a liquid crystal digital scanner-based head-mounted display (DS-HMD) that has been developed at Physical Optics Corporation (POC). The HMD consists of low power light emitting diodes (LEDs), a liquid crystal digital scanner, and image projection optics produced by POC's proprietary holography technology. Modulating the individual LEDs while synchronously scanning perpendicularly generates a 2D image. The paper describes design, fabrication, and performance measurements for an actually implemented experimental liquid crystal digital scanner system, and design and fabrication of the holographic components.
Soft computing is a set of promising computational tools for solving problems that are inherently well solved by humans but not by standard computing means. This paper presents an overview of R and D activities at Physical Optics Corporation in the area of soft computing. The company has been involved in soft computing for over ten years, and has pioneered several soft-computing methodologies, including fuzzied genetic algorithms and neuro-fuzzy networks. Several practical implementations of soft computing are discussed.
This paper presents a real-world application of neurofuzzy processing to a security system with multiple sensor. Integrating fuzzy logic with neural networks, the authors have automated the tasks of sensor data fusion and determination of false/true alarms, which currently rely solely on human monitoring operators, so that they operate in a way similar to human reasoning. This integrated security system includes a set of heterogeneous sensor. To take advantage of each sensor's strengths, they are positioned and integrated for side, accurate, economical coverage. The system includes real-time tracking cameras functioning as true digital motion detectors with the capability of approximating the size, direction, and number of intruders. The system is also capable of real-time image segmentation based on motion, and of image recognition based on neural networks.
An autopilot algorithm that controls a fighter aircraft in simulated aerial combat is presented. A fitness function, whose arguments are the control settings of the simulated fighter, is continuously maximized by a fuzzied genetic algorithm. Results are presented for one-to-one combat simulated on a personal computer. Generalization to many-to-many combat is discussed.
Physical Optics Corporation has developed an advanced 3-D virtual reality system for use with simulation tools for training technical and military personnel. This system avoids such drawbacks of other virtual reality (VR) systems as eye fatigue, headaches, and alignment for each viewer, all of which are due to the need to wear special VR goggles. The new system is based on direct viewing of an interactive environment. This innovative holographic multiplexed screen technology makes it unnecessary for the viewer to wear special goggles.
Physical Optics Corporation has developed a unique technology and processes to fabricate a 3D display system that does not require wearing glasses or other eyewear. The authors present the result of true 3D (T3D) monitor development, the third generation T3D being based on a holographic multiplexing screen. The monitor displays 3D autostereoscopic information to three viewers. Holographic multiplexing allows a large number of viewers to see the 3D effect without compromising resolution or having to wear any type of special glasses or goggles. The 3D monitor can deliver high resolution graphics -- 1024 X 480 pixels -- as well as NTSC video in both composite and S-video formats.
This paper presents an eye tracking system that combines optical and electronic image processing for the precise measurement of eye movement parameters, including direction, speed, and acceleration. The system applies optical joint Fourier transform correlator and novelty filtering to measure the cross-correlation peak displacement caused by eye movements using magnified images of iris landmark patterns. This permits a 0.026 degree(s) accuracy of eye displacement measurements within a 6 degree(s) tracking range, or a 0.1 degree(s) accuracy within a 20 degree(s) range. Using digital micromirror device SLMs in the Fourier transform optical system, an inverse Fourier transform DSP module, and a high-speed digital camera, the eye tracking system will make it possible to detect and characterize saccadic intrusions in smooth pursuit eye movement.
We describe here a multifunctional plasma diagnostic (MFPD) device being developed by Physical Optics Corporation using interferometry and spectroscopic techniques, along with an intelligent software package. The MFPD can provide a non- contact diagnosis of plasma density profile, temperature profile, and ionic species of plasmas. High-speed data processing is accomplished through automatic data acquisition hardware and an intelligent software package, which contains two major parts: (1) a genetic-algorithm- based, fast-evolved phase profile fitting program, and (2) an intelligent neural network spectral feature recognition and plasma classification routine. The integrated MFPD is user-friendly, real-time, simple to operate, and applicable to industrial environments.
A mutually pumped phase conjugator generates a phase- conjugate replica for each of two mutually incoherent incident optical beams interacting within a photorefractive crystal. This operation is useful for optical communication and interferometry. In this paper, we report a demonstration of mutual phase conjugation for light reflected from a diffuse surface. We studied the dependence of the phase- conjugation reflectivity on the parameters of the optical system. Finally, we built a mutually phase conjugating interferometer to detect the ultrasound vibration of a diffuse object to inspect defects inside it, based on laser generated ultrasound technology. The experimental results and analysis will be given.
An optical communication/switching system with data speeds well beyond any state-of-the-art electronic board-to-board computer interconnect is proposed. This interconnect is based on the use of microprism arrays to achieve large-scale, wideband interconnections for optoelectronic systems.
Holographic recording techniques have been applied to implement synthetic estimation filters (SEF) for pose estimation of a docking spacecraft. Each SEF is a weighted combination of Fourier-plane hologram exposures of different target attitudes. These particular attitudes represent a span of the attitudes among which the SEFs will ratiometrically interpolate the attitude of the target in an input image. The pose is estimated by comparing the correlation peak intensities for all the filters with previously stored reference intensity peaks.
The search for a dynamic recording medium that can be used in real time without the need for processing has become a critical issue in the development of practical neural network systems, correlators, all-optic switches, image and signal processors, and optical storage devices. A typical optical material respond to changes in the intensity, polarization, or wavelength of the illuminating light. The optical material developed and used for neural network applications responds to changes in the polarization of blur or green laser light. Implementing a neural network or performing optically-controlled acoustic beam steering requires a high-speed read/write/erase optical memory. POCs erasable dye polymer material offers a high read/write/erase data rate, nondestructive reading, fast data access, high storage density, overwrite capability, and long cycle life.
Fractal image processing technology has been recognized as having great potential in automatic target recognition (ATR) and image compression. In this paper, Physical Optics Corporation demonstrates the feasibility of using a fractal image processing technique as a new and efficient approach for signature, pattern, and object recognition. Using optical Fourier transform and a ring-wedge detection technique, we generate and measure the power spectral density of an input scene. The log-log plot of the power spectral density vs. spatial frequency provides a very valuable signature for each input. Experimental results show that we can successfully discriminate man-made objects from natural objects in input scenes by analyzing signatures obtained this way.
An all-optical reconfigurable crossbar switch is implemented by unique integration of dynamic photopolymer technology, simple geometry optics, and waveguide technology. This all-optical crossbar switch provides high reconfigurability, large fanout, and radiation hardening. These characteristics are essential for both parallel/distributed processing and high-bandwidth communication, especially for B-ISDN.
Optical interconnects have been designed, fabricated, and tested, and a graphics processor based on field-programmable gate arrays has been designed. The board-to-board connection approach is based on multi-channel integrated optical waveguides with novel optoelectronic active connectors, allowing multiple simultaneous data transfers among many boards. Data is transferred from chip to chip through optical data channels within an integrated chip. For electronic processing systems, we developed a preliminary design for a multiprocessor system suitable for both single instruction multiple data and multiple instruction multiple data, and using video random access memory and static random access memory for main memory, look-up table processing, and display interface.
Genetic algorithm performance has been improved by adaptively modifying genetic operators, and by filtering out recurring chromosomes from the fitness evaluation process. The enhanced genetic algorithm has been applied to neural network topology selection and function optimization. The performance of the algorithm was evaluated in multiple function and problem domains, where it showed superior convergence speed.
Artificial neural networks have proven to be powerful tools for sensor fusion, but they are not adaptable to sensor failure in a sensor suite. Physical Optics Corporation (POC) presents a new sensor fusion algorithm, applying fuzzy logic to give a neural network real-time adaptability to compensate for faulty sensors. Identifying data that originates from malfunctioning sensors, and excluding it from sensor fusion, allows the fuzzy neural network to achieve better results. A fuzzy logic-based functionality evaluator detects malfunctioning sensors in real time. A separate neural network is trained for each potential sensor failure situation. Since the number of possible sensor failure situations is large, the large number of neural networks is then fuzzified into a small number of fuzzy neural networks. Experimental results show the feasibility of the proposed approach -- the system correctly recognized airplane models in a computer simulation.
Optoelectronic SAR signal processing for real-time parallel adaptive on-board wide area surveillance and ATR applications is described. The signal processing architecture consists of a coarse ATR processor that performs early detection of small targets to select regions of interest in a large field of view, and a fine ATR processor for accurate classification of selected targets. Both coarse and fine ATR processors apply circular correlation-based algorithms implemented with optical joint transform correlators. Together with associative memory and genetic algorithm composite filtering, this discriminates among similar targets and rejects cluttered backgrounds.
Physical Optics Corporation (POC) has developed novel high- gain holographic non-Lambertian (HNL) screens for high- resolution flat panel displays, cockpit displays, and other military and commercial screen applications. These HNLs are composite holographic components that combine both diffusive and diffractive functions in a single element. These screens can control light energy distribution within a desired elliptical or circular cone and direction. As a result, the contrast and luminance of screens can be increased 10 times without any degradation in resolution. POCs HNL screens do not introduce any of the interference 'Moire' fringing that hinders the performance of lenticular screens. Additionally, the graded index properties of HNL screens eliminate all back-scattering losses, which in current scatterers are as high as 50 percent.
Physical Optics Corporation has developed an autostereoscopic 3D display system that does not require viewers to wear goggles. This system is based on a stationary holographic projection diffuser fabricated using volume multiphase holographic optical elements. Design and development of the prototype are also described.
We describe here a holographic non-destructive inspection (NDI) technology developed by Physical Optics Corporation. It is based on real-time holographic dye polymer materials and a shearographic camera, with neural network defect classification software. Holograms can be recorded in or erased from the new dye polymer material in a millisecond without wet processing, making real-time holographic NDI feasible. The shearographic NDI system, based on laser speckle interferometry, compensates for low-light conditions. Both holographic and shearographic fringes are input to the neural network system to perform automatic defect type classification.
The features and operation of an electro-optically switched binary optical time delay system are discussed. THe system based on polarization switching using the low cost ferro- electric liquid crystal and polarizing beam splitters provides compactness, low complexity, low insertion loss and arbitrary time delay. We present the design, component selection, fabrication, testing, and evaluation of a prototype.
Optical interconnects will play an increasingly significant role in future space applications, because of their high transmission bandwidth potential and radiation hardness. This paper presents the development results of a hybrid optoelectronic system comprising four electronic processing boards that communicate through an optical 3 by 3 non- blocking crossbar switch. Each processing board contains Tx and Rx modules pigtailed to multimode fibers. An optical fan-out of 1-to-3 is implemented by means of a holographic grating. The fan-in is implemented as a lens array. The system has been tested using dedicated automatic target recognition (ATR) software, and space testing is planned.
We report the results of the experimental studies on the fabrication of Fabry-Perot filters using holographic methods. High finesse holographic Fabry-Perot (HFP) filters can be fabricated using low quality substrates and commercially available volume holographic recording materials. Several large aperture samples of HFP filters were successfully fabricated using glass and plastic (mylar) spacers of thickness ranging from 5 micrometers to 6.6 cm. The finesse of these HFP samples was sufficiently high (approximately equals 30) and limited only by the absorption of the presently available holographic materials.
In this paper, the optical properties of broadband Lippmann-Bragg volume holographic mirrors are analyzed. These mirrors have a wavelength bandwidth much higher than their Bragg bandwidth, which is a result of Kogelnik's theory. While Kogelnik's model assumes uniform distribution of the distance between Bragg planes as a function of the vertical coordinate, the experimental results presented in this paper strongly demonstrate that Kogelnik's theory is not valid in the case of broadband Lippmann-Bragg volume holographic mirrors.
A brief review and discussion of ongoing research on radiation effects in key optoelectronic-photonic waveguide and periodic structures is presented. The review focuses on optoelectronic components composed of III-V and II-VI materials that are currently of interest in space applications. Reported and predicted radiation-induced responses in acousto-optic modulators, optical waveguide couplers, distributed Bragg reflectors, and organic materials are discussed.
Daylighting techniques are an effective means of reducing both lighting and cooling costs; however, many of the standard techniques have flaws which reduce their effectiveness. Daylighting holograms are an efficient and effective method for diffracting sunlight up onto the ceiling, deep in a room, without diffracting the light at eye-level. They need only cover the top half of a window to produce significant energy savings. They may be used as part of a new glazing system or as a retrofit to existing windows. These holograms are broadband and are able to passively track the movement of the sun across the sky, throughout the day and year.
A novel all-optic waveguide crossbar switch based on an in-house developed birefringent material is presented here. This switch uses visible light ((lambda) equals 514 nm) for programmable beam addressing to provide all-optic reconfiguration in both single-mode and multi-mode waveguides. An array of waveguide beams can be addressed within milliseconds using very moderate optical pumping powers (below 100 (mu) W). This allows green emitting diodes to be used for signal switching. The switch is characterized by high speed, high switching sensitivity, low waveguide loss, low optical noise levels, erasability, and reasonable cost.
Dispersion and aberration compensation techniques in diffractive optics and holography are reviewed. It is shown that the basic analyses of chromatic dispersion, and both types of Seidel aberrations (wavelength-related and geometric), apply for both holographic optical element (HOEs) and diffractive optical elements (DOEs), based on grating composition.
A new fractal dimensionality measurement and analysis-based automatic target recognition (ATR) is presented. ATR is a multi-step procedure, such as preprocessing, interest locating, segmenting, feature extracting, and classifying. Physical Optics Corporation has developed a new ATR system, based on fractal image processing, which can perform interest locating, segmenting and feature extraction simultaneously. Experimental results of the proof-of- principle is also presented.
A new automatic target recognition (ATR) technique called fractal transform is presented. The fractal transform is a combination of fractal image processing and the Hough transform. A measurement of the power spectral density (PSD) of an input scene was performed using a ring-wedge detector to obtain a log (PSP) vs. log (spatial frequency) plot. By analyzing the log-log plot by the Hough transform and a neural network, the ATR operation based on fractal transform is achieved.
In this paper, we report an optical bus fabrication technology using compression-molding technique. The linear dimension of such a waveguide is well beyond that of a microlithographically defined waveguide. The interconnection patterns such as fan-ins and fan- outs can be easily defined by the mold plunger. The resolution of compression molding can be as high as 2 micrometers . Therefore, optical bus density as high as approximately 104 channels/cm is producible while the linear dimension of the waveguide can be much larger than that made through conventional microlithography. Employment of optically transparent electronic packaging polymers (OTEPPs) as the system buses automatically provides process compatibility with silicon IC fabrication. All the polymer microstructure waveguide materials are either thermosets or thermoplastics. Both can be molded to a specific shape as desired.
The prospect of high density three-dimensional optical memory has encouraged development efforts. Research has focused on storing Bragg angle multiplexed hologram page storage and two-photon bit storage volumes. Physical Optics Corporation (POC) has investigated alternative multilayer 3-D memories based on a vectorial organic recording medium. POC's approach incorporates polarization vector switching to independently address layers in the third dimension. POC's methodology has been to fully characterize the molecular and bulk properties of the vectorial organic recording medium, optimize material performance for memory applications including cache and integrated waveguide, and investigate suitable three- dimensional optical memory storage architectures. Here we report on a promising architecture which we have recently demonstrated.
The speed of modern supercomputers is primarily limited by the relatively slow speed of memory. Research over the past years has focused on developing optical memory systems that, by nature of optics, promise to achieve high speed and high memory capacity. Three- dimensional optical memory systems are well known for their storage capacity and achievable short access time. But the early attempts to exploit 3-dimensional media were limited to photorefractive crystals such as lithium niobate, due to the unavailability of any other suitable medium (alternative media are precluded by their diffraction limited storage densities and non- erasable characteristics). Although volume phase holograms can be recorded in photorefractive crystals, these materials have many obvious flaws such as strong scattering, phase distortion, self diffraction, fast decay, and low refractive index modulation. There have also been continuous efforts to develop new 3-D media (such as photon echo, photorefractive polymers, bacteriorhodusphin, memory access cache, etc., but none can be applied in real world 3-D device because these materials are still in the early stage of development.
A polarization vectorial holographic recording medium has been investigated for the development of high performance three-dimensional optical memory storage architectures. The approach has been to fully characterize the molecular and bulk properties of the polarization vectorial holographic (PVH) recording medium, and to optimize material performance for memory applications. Response time, write/read/erase speed, and fatigue of the PVH medium have been dramatically improved. The response time has been reduced to 80 μs. No material fatigue has been observed in over one million read/write/erase cycles. We also demonstrated high-speed (< 1 kHz) write/read/erase cycling. These improvements are the result of a detailed investigation of the molecular photophysics which allowed the optimization of material and recording parameters.
Azo dye polymers have been investigated as polarization holographic recording and all-optical modulating media. The use of azo dye polymers is limited by their intrinsic low response time. Different dyes and fabrication techniques have been utilized to enhance the material's speed. A relatively new modulation technique utilizing the nonlinear Fabry-Perot effect in attenuated total internal reflection (ATR) geometry is compared to the conventional transmission type modulation geometry. In the ATR case, a small change in the index of the polymer causes a shift in the angular spectrum of the Fabry-Perot resonances, thus enabling us to modulate a probe beam with an external pump beam. Both modulation speed and contrast ratio are greatly enhanced using this technique. Experimental results are presented, and the limits of both methods are analyzed. The ATR method is also useful in characterizing thin (less than a few microns) polymer films, for studying photo-induced index changes. Future applications, such as optically addressed spatial light modulators and nonlinear optical processing applications, are discussed.
Thus far, network modules have mostly been implemented on computers and electronic hardware with low density interconnections at low speed. Optics potentially offers high density parallel interconnections at high speed. However, the implementation has been limited to single layer machines. As a result, no practical implementation has yet been reported. The lack of suitable materials providing dense synaptic interconnections is the primary reason for the slow progress in the practicality of optical neural network implementation. Photorefractives are considered as suitable materials. However, photorefractives have inherent problems including scattering, sensitivity, low refractive index modulation and fast decay. Furthermore, optical network systems based on photorefractives have low signal-to-noise ratio, have poor stability, and cannot realize error driven learning algorithms, such as the back error propagation. In addition, low diffraction efficiency severely affects cascadability of neural layers. Therefore, multilayer machines using photorefractive crystals are difficult to implement. Physical Optics Corporation (POC) has developed a new dynamic birefringent material for recording polarization holograms with selective enhancement or erasure in real time. Extensive investigation has shown that POC's material offers well-controlled dynamic behavior that is superior to photorefractive crystals, Polaroid DMP-128, Du Pont photopolymer and Kodak's silver halide for neural network interconnection applications.
A new holographic recording medium based on poly-2-Hydroxyethyl Methacrylate (HEMA) and visible light sensitizer is investigated. The holographic recordings are based on photo- induced polymerization of HEMA, using Camphorquinone as a visible light sensitizer. The medium has several advantages. Namely, it does not require extensive processing and survives high humidity conditions, including water immersion. Several experiments have been conducted to analyze the behavior of this medium, including analysis of recording parameters using a real-time holographic recording/playback setup, precuring, swelling, and water survivability tests. Water-immersion survivability of our material is a unique characteristic that can be incorporated in novel holographic and optical systems, such as water immersed holographic optical elements. New possibilities and applications are discussed.
The increased emphasis on speed of operation, wavelength selectivity, compactness, and ruggedization has focused a great deal of attention on the solutions offered by all-optic devices and by hybrid electro-optic systems. In fact, many photonic devices are being considered for use as partial replacements for electronic systems. Optical components, which include modulators, switches, 3-D memory storage devices, wavelength division multiplexers, holographic optical elements, and others, are examples of such devices. The success or failure of these modern optical devices depends, to a great extent, on the performance and survivability of the optical materials used. This is particularly true for volume holographic filters, organic memory media, second- and third-order nonlinear material-based processors and neural networks. Due to the critical importance of these materials and their lack of availability, Physical Optics Corporation (POC) undertook a global advanced optical materials program which has enabled it to introduce several optical devices, based on the new and improved materials which will be described in this article.
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