Wheatstone invented the first stereoscopic display on record in 1834. Numerous approaches to the display of stereo imagery have been demonstrated since; however, all suffer from various drawbacks. Stereoscopic displays typically require the user to wear special headgear. Autostereoscopic displays typically have tight limitations on the position of the viewer's head. We investigate an architecture consisting of two readily available, inexpensive twisted nematic liquid crystal display (TN-LCD) panels sandwiched together to form a compact, rugged stereoscopic display. We describe the theory of operation, the experimental determination of the liquid crystal display modulation characteristics, and modifications to the theory of operation, as a consequence of the experimental results.
The benefits of stereo vision are numerous and quickly become apparent when attempting to perform simple tasks without the aid of stereo cues. The proliferation of remotely operated vehicles and indirect viewing applications has resulted in an increased need to see the operational environment in stereo. Several approaches to the display of stereo imagery have been demonstrated. Stereoscopic displays typically require the user to wear special headgear. Autostereoscopic displays require no headgear but typically have tight limitations on the position of the viewer's head.
Previous papers have described a new type of stereoscopic display based on dual liquid crystal displays. The new display provides a stereo view without temporal or spatial multiplexing. Several prototype displays have been built and demonstrated to potential users with favorable reviews. With a successful proof-of-principle prototype completed, the effort is focusing on improvements to the image quality, consolidating the electronics, and packaging the display for use in rugged environments. The results of this effort should produce a rugged, compact, multiuse stereo display.
The proliferation of remotely operated vehicles (ROVs) has resulted in a need for the capability to see the operational environment in stereo. In a previous paper the theoretical underpinnings for new types of stereoscopic and autostereoscopic flat-panel displays with full-time, full-resolution images (i.e., no temporal multiplexing and no spatial multiplexing) were presented. Recently, a stereoscopic prototype has been constructed at the U.S. Army Aviation & Missile RDEC and testing is underway. The research presented here describes the application of two liquid crystal displays (LCD) sandwiched together to form a compact, rugged stereoscopic display. Polarized glasses are used to view the image in stereo. The prototype provides a full-time, full-resolution stereoscopic 3D display in a package slightly thicker, but no larger, than the standard liquid crystal display used in laptop computers. The LCDs have been characterized using a Stokes vector polarimeter. The characterization results were very interesting and led to some changes in the encoding algorithms. Significant improvements in the display quality were achieved through these adaptations.
Stereo imagery has been a goal in optics research since the invention of the stereoscope in 1834. While the market has been inundated with displays of various types, sizes, and formats, no general purpose, easy to use, inexpensive method for the display of imagery in stereo has been developed. The benefits of stereo vision are numerous and quickly become apparent when attempting to perform simple tasks without the aid of stereo cues. The proliferation of remotely operated vehicles and indirect view applications has resulted in an increased need to see the operational environment in stereo. Numerous approaches to the display of stereo imagery have been demonstrated. Stereoscopic displays typically require the user to wear special headgear. Autostereoscopic displays, so named because they do not require the headgear, typically have tight limitations on the position of the viewer’s head. Previous papers have described the theoretical underpinnings for new type of stereoscopic displayed based on dual liquid crystal displays. The new display provides a stereo view without temporal or spatial multiplexing. This paper will present the results from experiments to characterize the display components and the resulting changes in the encoding algorithm.
Stereo imagery has been a goal in optics research since the invention of the stereoscope in 1834. While the market has been inundated with displays of various types, sizes, and formats, no general purpose, easy to use, inexpensive method for the display of imagery in stereo has been developed. The benefits of stereo vision are numerous and quickly become apparent when attempting to perform simple tasks without the aid of stereo cues. Numerous approaches to the display of stereo imagery have been demonstrated. Stereoscopic displays typically require the user to wear special headgear. Autostereoscopic displays, so named because they do not require the headgear, typically have tight limitations on the position of the viewer's head. The research proposed here will investigate the application of two readily available, inexpensive liquid crystal panels sandwiched together to form a compact, rugged stereoscopic display. The appropriate drive signals are provided to the two stacked panels, which encode in polarization, the left and right images. Standard polarized 3D glasses can then be used to view the image in stereo. The proposed display will provide stereo pairs without loss of resolution or frame rate and without strict limitations on the placement of the viewer’s head.
A stereoscopic or autostereoscopic display based on this technology provides full resolution and freedom of movement, but with no flicker. Simply put, the display is neither spatially nor temporally multiplexed. It sounds unbelievable, but it's true -- an autostereoscopic display where each eye sees every displayable pixel on the screen at all times. This technology is designed for flat-panel displays, such as LCDs and has the following characteristics: (1) The display is not spatially multiplexed. Each eye sees the full native resolution of the entire screen. (2) The display is not temporally multiplexed. The image for each eye is visible continuously, i.e., at all times. (3) In its simplest form, this technology provides a full-time, full-resolution stereoscopic display for multiple viewers wearing passive polarizing glasses. (4) A variation of this technology can be used to make a full-time, full-resolution stereoscopic projection system for viewers wearing passive polarizing glasses using just a single projector. (5) With the addition of a dynamic aiming mechanism, and an adjustment in the display's output, we can create a single-user, full-time, full-resolution autostereoscopic display requiring no glasses and providing full freedom of movement. Software applications can use the same information about viewwer position to provide natural, full "look-around." (6) A hybrid version of the display can alternate between autostereoscopic (single-user, no glasses) and stereoscopic modes (multi-user, passive glasses).
Pulse couple neural networks (PCNN) have demonstrated some very desirable properties. Chief among these is its ability to segment images very rapidly and very well. This capability has been demonstrated with many different types of imagery including synthetic aperture radar imagery, infrared imagery, optical correlator output imagery, and medical diagnostic imagery. Most of the implementations of this network have been done in software. Several attempts have been made to build electronic versions with varying degrees of success. Recently, an Army Phase II SBIR was awarded to incorporate a PCNN in a smart detector for both military and medical applications. One of the inherent difficulties in building an electronic PCNN is implementing the linking field that is the strength of this network. An optical implementation of the linking would potentially simplify the problem and take advantage of the inherent parallelism of optics. The resultant hardware could be simpler and faster than previous implementations making it an attractive solution. This paper will discuss the current status of the SBIR program, and present possible optical implementations using recently developed Vertical Cavity Surface Emitting Laser arrays.
Optical correlators using spatial light modulators in the filter plane have been discussed and presented for many years. In most cases, these devices are electrically addressed modulators and the filters are generated off-line in software. These filters can be tailored to fit the desired application but cannot be adjusted to account for real-time changes in the target appearance. In addition, building filters to account for all of the possible viewing configurations can strain the reference database and the memory storage capability of the system. Recently, a correlator architecture that used an optically addressed, multiple quantum well (MQW) spatial light modulator as the filter plane device was presented. The architecture is a modified Vander Lugt correlator with and additional input modulator. The filter formed by the interference of the reference image beam and the reference beam is recorded on the MQW spatial light modulator. The recorded filter retains the full complex information as high-resolution film did years ago. Additionally, the filter can be updated simply by changing the pattern on the reference input modulator. The second input modulator is used to address this stored filter in a normal correlator read-out configuration. The correlator has been completed and results will be presented as part of this paper.
Poor performance in key components has limited the development of optical target recognition systems. New components are now available, however, that exhibit size and speed characteristics compatible with image processing applications. The U.S. Army Aviation and Missile Command is well known for acquiring and testing a variety of spatial light modulators for image processing applications. We have recently acquired a pair of Sanders Multiple Quantum Well Spatial Light Modulators. These modulators will be evaluated in a manner similar to that used with previous modulators to determine contrast ratio, switching characteristics, optical efficiency, and residual phase modulation. The results of these measurements will be presented.
A vanderLugt correlator is under construction using two Sanders binary Multiple Quantum Well Spatial Light Modulators. This correlation is part of the U.S. Army Aviation and Missile Command's three-year program to evaluate the latest generation hardware available for image processing. The Sanders modulators offer extremely high frame rates that make them attractive for image processing applications. The limiting factor in this correlator will actually be the output detector rather than the spatial light modulator. The correlator will be evaluated using infrared imagery to determine its performance in a target cueing/target screening applications. The results from these experiments as well as future plans will be presented.
Poor performance in key components has limited the development of optical target recognition systems. New components are now available, however, that exhibit size and speed characteristics compatible with image processing applications. The U.S. Army Aviation & Missile Command has recently begun a program to exploit the new devices for both homing and imagery analysis applications. New architectures and algorithms which exploit the modulation characteristics of the new devices are being developed and tested. Part of the program is also aimed at funding improvements in the devices to better meet the requirements for optical target recognition. This paper will discuss the overall program, specific devices under consideration, and present the architectures and algorithms under development. Any experimental results available at the time will also be presented, with more detailed results to be presented at a later conference.
We review GaAs Fabry-Perot vertical cavity multiple quantum well (MQW) spatial light modulators (SLMs) developed at Sanders, a Lockheed Martin Company, and demonstrate their use in optical image correlation. These MQW SLMs are reflective- mode modulators using electrically-tunable absorption to modulate the reflected intensity. The operation of the MQW SLMs with a newly-developed Labview graphical user interface is described. A compact Vander-Lugt image correlator is described which was configured using MQW SLMs: binary 128 X 128 pixel image input with a binary filter plane. In addition, the architecture of 8-bit gray-scale MQW-SLM module developed at Sanders is discussed. The performance of the image correlator was characterized using amplitude-encoded binary phase-only filters and various test targets including test imagery supplied by US Army AMCOM, and is compared with simulations for peak-to-secondary efficiencies on these data. Finally, high-speed (250,000 frames per second) target recognition of 128 X 128 pixels binary input imagery is demonstrated.
A major concern in high speed, aided target recognition is getting enough information through the system, in the shortest possible time, to cover the desired targets while maintaining good target detection performance. With composite filter techniques, one can design a filter to respond over a range of scale and orientation for one target, and therefore, reduce the time required for a complete filter search. A variety of compositing techniques have been discussed on many occasions, and all have advantages and disadvantages. With available spatial light modulator technology, one must implement composite filters on devices with limited modulation states. Juday and others have proposed techniques for mapping desired filter functions onto these devices. This paper will present a filter generation methodology which combines Juday's mapping method with the MACE algorithm for generating composite filters.
A 32-channel system has been designed and built to process large-format synthetic aperture radar imagery. Eight Vander Lugt optical correlators operate in parallel, controlled by a single-board VME computer. The full-size images are divided into subscenes to match the processors' SLMs and compared to a stored filter bank. Each correlator incorporates two LCDs, four diffractive optical elements, a large CCD sensor, and a DSP based neural network post- processor. Custom drive electronics derive the LCDs at 60 Hz and double their normal operating resolution. The system is self-calibrating and automatically adjusts for a failure in any of the 8 processors. This paper will present a system level overview and discussion of each of the major sub- systems.
Automatic target recognition has a wide range of applications spanning many different imagery formats. These input formats include, but are not limited to video, infrared imagery, and synthetic aperture radar imagery. Optical correlators, while not the total ATR solution, have the potential to aid in this complex task. One area of recent interest has been near and far field effects in synthetic aperture radar imagery. An optical correlator has been used to qualitatively assess the differences in imagery obtained for both the near and far field cases. Reference filters were made for each case and compared to imagery from the opposite case. The results of these experiments will be presented.
A new drive circuit for the liquid crystal display (LCD) of the InFocus TVT-6000 video projector is currently under development at the U.S. Army Missile Command. The new circuit will allow individual pixel control of the LCD and increase the frame rate by a factor of two while yielding a major reduction in space and power requirements. This paper will discuss results of the effort to date.
Liquid crystal televisions are popular low-cost spatial light modulators. One LCTV of interest is found in the InFocus TVT-6000 television projector. A wavefront splitting interferometer has been constructed and analyzed for measuring the complex characteristics of these modulators, including phase and amplitude coupling. The results of this evaluation using the TVT-6000 projector drive electronics have been presented in a previous work. This work will present results of the complex characterizations of these modulators using custom drive electronics.
Composite filters offer one solution to the problem of scanning numerous filters to find a single target at any aspect, orientation, or configuration. Many different techniques for generating composite filters exist, each with their own advantages and disadvantages. Liquid crystal televisions are an increasingly popular choice for spatial light modulators and are characterized by a coupled phase and amplitude response. The coupled response can cause a problem if not accounted for, however, it can also be used to more closely approximate the desired filter response. This paper will present the results of using optimally encoded composite filters on a LCTV for optical pattern recognition applications.
Liquid crystal televisions have become increasingly popular as low-cost spatial light modulators. While the early devices suffered from poor resolution and low contrast, recent models compare favorably to the more traditional (and expensive) modulators. One of the most recent LCTVs is found in the InFocus TVT-6000 television projector. The panels in this projector have 480 X 440 pixels with a 1.32' diagonal clear aperture. A wavefront splitting interferometer has been constructed and analyzed for measuring the complex characteristics of these modulators, including phase and amplitude coupling. The results of this evaluation will be presented.
Extremely light efficient optical correlators can be built if both the input and filter are displayed on phase modulating devices. Problems may exist, however, since changes in the input scene intensity cause changes in the phase encoding. An analysis is presented here for the VanderLugt correlator architecture. Experimental results comparing the correlator response to phase-encoded and amplitude-encoded inputs are also presented for varying input scene intensities.
The amplitude- and phase-modulating properties of liquid crystal televisions (LCTVs) are becoming increasingly well known. The Epson Crystal Image video projector is a relatively new TV and uses three liquid crystal panels to encode the red, green, and blue components of the video signal onto the projector light. These panels can be removed for use in optical systems. We present the results from measurements of the phase- and amplitude-modulation properties of one of these LCTV panels.
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