Prototypes of projection displays based on dispersions of liquid crystal in polymer matrices are beginning to appear. The principle of operation depends on electrically switchable light scattering. They are potentially much brighter than current cathode ray tube (CRT) or twisted nematic liquid crystal (TN LC) cell based displays. Comparisons of efficacy and efficiency show this. The contrast and brightness of such displays depend on a combination of the f- number of the projection system and the scattering characteristics of the light valve. Simplified equations can be derived to show these effects. The degree of scattering of current NCAP formulations is sufficient to produce good contrast projection displays, at convenient voltages, that are around three times brighter than TN LC projectors because of the lack of polarizers in the former.
Recent focus on the development of HDTV systems worldwide has raised a critical concern--the economic viability of HDTV for the home marketplace. While projection systems performing at or above HDTV-quality levels exist today, they are designed for the institutional market and are priced far above the threshold for the individual consumer. Manufacturers will be under considerable pressure to significantly reduce the cost of HDTV projectors, as will the suppliers of key components such as lenses. Fortunately, recent developments have been made in the design, development and manufacturing technologies used to produce hybrid lenses for high-performance projection systems. This is particularly true for CRT-based front- and rear-projection systems for data and graphics applications. Extending these advances to HDTV would suggest that by the time HDTV is ready for high volume mass production, cost-effective projection lenses will be enhancing, not retarding, the market acceptance of HDTV.
The laser-addressed ferroelectric liquid crystal light valve (FLCLV) consists of metal-insulator-semiconductor (MIS) photoconductive sensor and ferroelectric liquid crystal (FLC). It has a high resolving power of 50 1p/mm for laser pulse recording and 130 1p/mm for 2-dimensional image recording. The multibeam laser scanning method is applied in this display system, which achieves high writing speed (0.5 s/frame) and high resolution (1500 X 1600 pixels--higher than that of HDTV.
Various types of front and rear projection screens are analyzed and their specific performance benefits and deficiencies discussed. Problems unique to the projection of high-definition television images will be considered, such as screen element resolution and overall image brightness. The importance of new and more efficient projection systems as they relate to the future of high-definition television projection is outlined. Particular emphasis is placed on the importance of early consideration of the projection screen surface in the overall system design. The latest advances in projection screen technology are discussed, along with some speculation about future screen designs.
A prototype laser video projector which uses electronic, optical, and mechanical means to project a television picture is described. With the primary goal of commercial viability, the price/performance ratio of the chosen means is critical. The fundamental requirement has been to achieve high brightness, high definition images of at least movie-theater size, at a cost comparable with other existing large-screen video projection technologies, while having the opportunity of developing and exploiting the unique properties of the laser projected image, such as its infinite depth-of-field. Two argon lasers are used in combination with a dye laser to achieve a range of colors which, despite not being identical to those of a CRT, prove to be subjectively acceptable. Acousto-optic modulation in combination with a rotary polygon scanner, digital video line stores, novel specialized electro-optics, and a galvanometric frame scanner form the basis of the projection technique achieving a 30 MHz video bandwidth, high- definition scan rates (1125/60 and 1250/50), high contrast ratio, and good optical efficiency. Auditorium projection of HDTV pictures wider than 20 meters are possible. Applications including 360 degree(s) projection and 3-D video provide further scope for exploitation of the HD laser video projector.
Vast resources are being spent on three continents, preparing for the commercialization of HDTV. The forces that together will launch this new industry are moving at dizzying speeds. This paper covers the highlights of events past and present and offers some predictions for the future. Difficult standards problems that keep brakes on the industry, and that will continue for some time to come. Standards committees have been set up around the world and are hard at work. It is a job with considerable technical and political challenges. By the time major plans and resources come together for commercialization of HDTV, one can trust that there will be adequately stable standards. But to observe the current status is to see a mess. High definition is not only consumer television. Because of its versatility, it is much more likely to find its way first into areas offering high returns such as medicine, education, printing, corporate communications, military and space, and even criminal control. HDTV is very likely to deliver movies and cultural events to theaters, and may also become the platform for a new generation of computers.
The demand for a true color LCD projection panel for use with standard overhead projectors has been around ever since the first monochrome OHP projection panel was introduced in 1986. The monochrome panels evolved along with the LCD technology from the first blue- and-yellow mode units to black-and-white with levels of gray, and to yellow-and-magenta panels with limited intermediate color shades known as pseudo-color. Finally, a novel solution has been implemented using a stack of custom designed STN panels, making possible true color LCD projection panels that are reasonably priced, available in high volume and quite acceptable in overall image quality. This stacked technology relies on the inherent birefringence colors of each layer to switch between white (passing all wavelengths) and a subtractive color primary (passing all wavelengths but red, green, or blue) so the full spectrum can be projected. Standard gray-scale techniques expand the displayable color palette to almost 5,000 colors and beyond. The same technology can also be applied to various self-contained projection architectures.
Helmet-mounted sight systems track the helmet angular orientation, thereby allowing the user to readily point weapons and sensors or to cue viewing among crew members. Most helmet- mounted display applications require that the helmet orientation be measured so that the displayed information can be properly presented. Helmet-mounted sights, also referred to as head trackers or helmet trackers, have been mechanized using a variety of technologies, each having apparent advantages. The leading technology candidates include magnetic, electro- optic, and ultrasonic head tracking systems. The selection of a particular concept is usually dependent on the specific application and the associated operational requirements. A technology overview is presented describing various electro-optic, ultrasonic, and magnetic mechanizations that have been developed. The performance characteristics are summarized with an indication of the strengths and weaknesses inherent in each approach.
The results of tests conducted with helmet-mounted sights (HMS) and helmet- mounted displays (HMD) are presented. To compare the accuracy of the different HMS systems (on a magnetic, acoustic, or optical basis) the authors find and unify a test procedure for verification. The test conditions vary, depending on the principle of the HMS system. Magnetic systems should be tested with the influence of magnetic disturbances, ultrasonic systems with the occurrence of noise and changing characteristics of the dispersion medium, and optical systems under high luminance to check saturation effects of the sensors. Modern integrated helmets (IH) consist of CRTs for displaying binocular images of TV--or infrared--cameras and superimposed symbology and a second channel with image intensifier tubes (IIT). Important points for checking CRTs are the resolution, distortion, homogeneity, and brightness in day and night. The most important test for the IIT channel is the resolution measured as a function of luminance of the test pattern. Tests of the basic helmet regarding head fit, earphone, center of gravity, weight, etc., are also necessary because these properties have an influence on the performance of the complete man-machine system.
A partial binocular-overlap helmet-mounted display (HMD) allows the presentation of wide-field-of-view imagery with no loss of resolution and a reduction in size and weight. One trade-off with these attributes is binocular rivalry created by the edge of the imagery seen by one eye overlaying continuous imagery seen by the other eye. Three distinct methods are considered that reduce this rivalry--and there are trade-offs with each approach. These three methods are the use of optical stops or filters that provide a luminance gradation that softens the overlapping binocular edges, left/right eye assignment for the flanking monocular regions, and contour lines superimposed on the imagery that correspond to the binocular/monocular borders. These approaches to improving the quality of partial binocular- overlap HMD imagery are considered within an ecological framework, where departures from ecological validity may impact visual perception and system performance.
The human ability to derive control-oriented visual field information from tele-operated helmet-mounted displays (HMDs) in nap-of-the-earth flight is investigated. The visual field with these types of displays originates from a forward looking infrared radiation camera, gimbal-mounted at the front of the aircraft and slaved to the pilot''s line-of-sight to obtain wide-angle visual coverage. Although these displays are proven effective in Apache and Cobra helicopter night operations, they demand very high pilot proficiency and work load. Experimental work presented in the paper has shown that part of the difficulties encountered in vehicular control by means of these displays can be attributed to the narrow viewing aperture and head/camera slaving system phase lags. Both these shortcomings will impair visuo- vestibular coordination, when voluntary head rotation is present. This might result in errors in estimating the control-oriented visual field information vital in vehicular control, such as the vehicle yaw rate or the anticipated flight path, or might even lead to visuo-vestibular conflicts (motion sickness). Since, under these conditions, the pilot will tend to minimize head rotation, the full wide-angle coverage of the HMD, provided by the line-of-sight slaving system, is not always fully utilized.
In a visor-projected helmet-mounted display (HMD), the volume and helmet shape are constrained by visor curvature and location. An approach is presented which determines optimal visor and optical configurations which lead to minimal helmet envelope size. A model based on a spherical visor and a criterion for an envelope size is defined. Three parameters are left free to be set by the designer: visor curvature, eye relief, and a degree of optical assembly obscuration. The influence of these free parameters on helmet size and shape are examined for an unobscured field of view. An adaptation of the model for nonspherical visors is also discussed.
A holographic optical element (HOE) can serve both as an imaging lens and a combiner for the helmet-mounted display. The resulting image is created by points whose geometrical conditions at readout will differ from those at recording, and then severe aberrations occur. Using the method of Hasman and Friesem, the authors design an optimal single reflective holographic helmet display element. This theoretical method is based on an analytic ray-tracing procedure that uses the minimization of the mean-squared difference of the propagation vector components between the actual output wavefronts and the desired output wavefronts. Considering the two-dimensional and monochromatic case, the authors obtain integral equations for the optimal grating vector components that they solve. As an illustration, the grating vector is calculated and the performance of a holographic helmet display with a 16 deg X 16 deg field of view is determined. Spot sizes and distortions at the image plane and the mean-squared difference of the propagation vectors are determined, and the results are compared with the performance of an HOE recorded with a spherical wave and a plane wave.
Realizing that the cost per channel of computerized scene generation would likely drop rapidly in the future and that the cost of visual projectors was similarly decreasing, the authors concluded that a full field-of-view display, consisting of many scene generation channels and projectors, could become economically feasible. Phase I of this project was tested by installing eight rear screen projectors on eight facets of a dodecahedron, and driving it with six channels of an existing scene generator. The result was a very bright, high-contrast display that has been most pleasing to all who have seen it. Phase II development attempts to increase resolution. While the resolution obtained in Phase I is sufficient for many tasks, it is inadequate for some air-to-ground weapon delivery tasks and longer range interaction with aircraft in air-to-air engagements. Phase II adds a two level of resolution, low cost, light weight, high resolution helmet mounted display. The result will be an affordable high performance display system.
In a cockpit, the crewstation of an airplane, the ability of the pilot to unambiguously perceive rapidly changing information both internal and external to the crewstation is critical. To assess the impact of crewstation design decisions on the pilot''s ability to perceive information, the designer needs a means of evaluating the trade-offs that result from different designs. The Visibility Modeling Tool (VMT) provides the designer with a CAD tool for assessing these trade-offs. It combines the technologies of computer graphics, computational geometry, human performance modeling and equipment modeling into a computer-based interactive design tool. Through a simple interactive interface, a designer can manipulate design parameters such as the geometry of the cockpit, environmental factors such as ambient lighting, pilot parameters such as point of regard and adaptation state, and equipment parameters such as the location of displays, their size and the contrast of displayed symbology. VMT provides an end-to-end analysis that answers questions such as ''Will the pilot be able to read the display?'' Performance data can be projected, in the form of 3D contours, into the crewstation graphic model, providing the designer with a footprint of the operator''s visual capabilities, defining, for example, the regions in which fonts of a particular type, size and contrast can be read without error. Geometrical data such as the pilot''s volume field of view, occlusions caused by facial geometry, helmet margins, and objects in the crewstation can also be projected into the crewstation graphic model with respect to the coordinates of the aviator''s eyes and fixation point. The intersections of the projections with objects in the crewstation, delineate the area of coverage, masking, or occlusion associated with the objects. Objects in the crewstation space can be projected onto models of the operator''s retinas. These projections can be used to provide the designer with the retinal coordinates and the visual angles subtended by objects in the crewstation space. Both the right and left eye retinal projections are mapped. The retinal map is yoked to the fixation point and changes as the fixation point is interactively manipulated. Performance contours on the retinas can also be indicated thus, aiding the designer in understanding the limitations to visibility imposed by retinotopic processing.
This paper examines the relationship between the display representation of a database and the type of task performed with the data in a multidimensional data visualization task. Subjects answered a range of questions about an economic database while viewing either a 2-D or 3-D display of a subset of the database. Subjects'' performance on the questions is interpreted within the context of the Proximity Compatibility Principle, a theory-based principle of the perceptual/cognitive interface. Implications for the design of data visualization display interfaces are discussed.
Colorimetry was found early on to correlate well neither to perceived brightness nor to perceived color. But modern psychophysics, aided by spectroradiometry, reveals the three spectral regions to which the normal human visual system responds most strongly. Light intended to carry information to the human observer, with maximum information throughput per watt content of the light, should best concentrate its power content near 450 nm, 530 nm, and 610 nm.
As the sophistication and power of computer systems continues to increase, the need for simplicity of human interface increases. The requirement to make systems ''accessible'' and ''friendly'' to the user is fundamental for the success of the system. While the development of touch input devices has opened the door to the possibility of incorporating the simplest user actions (i.e., looking and pointing) to control the operation of complex systems, the performance of these input devices has often not met the application''s requirements. The difference between the limits of the technology versus the current implementation of the technology has become clouded. The current implementation of the technology has not produced a product that represents the fully developed state of design, by example, of what the technology is capable of. Improvements in the operation of touch input devices are necessary for the realization of the goal of improved human interfacing to complex systems and overall system performance.
The instantaneous field of view (IFOV) of head-up display (HUD) systems is often enlarged by using a double combiner. Each combiner provides a partial field of view, with a degree of overlap between them. In a HUD with a double combiner a particular aberration arises consisting of an angular discrepancy between the images reflected from the two combiners. It generally causes an increase in the line width in the overlapping area of the field of view. In the extreme case a double image will appear. The problem can be partially solved by introducing a small angle between the combiners. However, this eliminates the aberration only at a single point in the field of view. A more comprehensive solution is provided by special design of the projecting lens system. The lens will have smaller aberrations at the center of the field of view, which includes the area of overlap of the two combiners, at the expense of the outer part of the field. This is usually a practical solution as the accuracy required in a HUD system is generally less stringent at larger field angles.
The method employs an electronically tunable light filter, which is integrated into an electronically controlled system. This paper discusses details of the design as well as principles of physics upon which the design is based.
Processing steps are discussed in detail. This new thin film transistor (TFT) is similar to the traditional tri-layer, inverted, staggered TFT in the cross-section view, but different in the top view. It has a self-aligned semiconductor island and source/drain contact vias. The process is composed of one mask alignment step (with two masks), one backlight exposure step, and four etching steps. Compared with the conventional, complicated process, its process time is shorter, its process window is wider, and there is less consumption of chemicals. Important factors of the backlight exposure lithography, such as the light source, intensity profile along the path, exposure energy, and photoresist profile, are examined. Other alternative processing methods for preparing the same kind of TFT are also presented. Issues regarding the application of this TFT to liquid crystal displays are discussed.
Programmable LED matrix display push buttons may greatly increase the performances of the computer-based avionic systems. The number of switches in a control panel can be reduced by a factor of 10 or more. This leads to a reduction in weight and size of the control instrumentations and in shorter response time of pilots. This work deals with the study and the optimization of visual performances of these displays in a configuration requiring a low- power consumption and Night Vision Goggles (NVG) compatibility. In considering displays for avionic applications, it is important to take into account sunlight readability. Visibility problems may arise in high ambient illumination. Up to now the only contributions usually considered for reduction of visibility are the diffused and specular reflected luminances that predominate with the sun behind the pilot. But there is another critical condition--the sun in front of the pilot. In this case the equivalent veiling glare predominates. Display performances and contrast enhancement filter characteristics must be optimized to find a compromise between these two extreme ambient conditions. Considering a keyboard with 10 push buttons, with two lines of four characters each and a power consumption less than 14 W with 40 of LEDs on, the authors have obtained good sunlight readability, choosing an optimized combination of NVG and contrast enhancement filter and LED matrix display.
This paper introduces processing techniques for AC plasma display devices which we have used in the development of singlesubstrate full color plasma research display devices and more recently have utilized in the fabrication of our ribbed twin substrate devices. These techniques Include: (1) photolithographic liftoff for the generation of high conductivity electrode arrays (2) novel thickfilm depositions and processes for the generation of thick dielectric structures used in the formation of isolation barriers and for selective phosphor placement (3) multilayer depositions of thinfilm dielectrics suitable for the formation of active pixel regions with high capacitance. These techniques make possible the fabrication of large size high resolution high density full color devices with reduced parasitic capacitances minimal optical crosstalk and sufficient linear levels of gray scale for video applications.
The emergence of computerized mission planning systems (MPS) and airborne digital moving map systems (DMS) has necessitated the development of a global database of raster aeronautical chart data specifically designed for input to these systems. The Naval Oceanographic and Atmospheric Research Laboratory''s (NOARL) Map Data Formatting Facility (MDFF) is presently dedicated to supporting these avionic display systems with the development of the Compressed Aeronautical Chart (CAC) database on Compact Disk Read Only Memory (CDROM) optical discs. The MDFF is also developing a series of aircraft-specific Write-Once Read Many (WORM) optical discs. NOARL has initiated a comprehensive research program aimed at improving the pilots'' moving map displays current research efforts include the development of an alternate image compression technique and generation of a standard set of color palettes. The CAC database will provide digital aeronautical chart data in six different scales. CAC is derived from the Defense Mapping Agency''s (DMA) Equal Arc-second (ARC) Digitized Raster Graphics (ADRG) a series of scanned aeronautical charts. NOARL processes ADRG to tailor the chart image resolution to that of the DMS display while reducing storage requirements through image compression techniques. CAC is being distributed by DMA as a library of CDROMs.
This paper describes improved design and implementation of real-time eye movement data acquisition and monitoring system. The main object of the system design is to provide a more practical environment, which allows less restriction on subjects'' head displacement and eliminates tedious optical mirror adjustments. An eye-mark recorder is used as the input device to measure the x-y coordinates of eye movements relative to a subject''s head. In addition, the continuous front view image is taken by a video camera set on the subject''s head. A CRT display is placed in front of the subject. The subject is shown visual objects displayed on the screen and asked to avoid deliberate head motion. Eight infrared LED reference points invisible to the subject are fixed on the screen. These points are used to calibrate the head displacement. First, a set of nonlinear photogrammetric equations including trigonometric functions are developed to relate the reference points to the camera displacements. Second, the equations are linearized for faster calculations. The errors caused by the approximation are evaluated. It is concluded that the linear equations give satisfactory results considering the physical configurations. A set of typical experiment results are shown to demonstrate the system performance.
Nonimaging holographic optical elements (HOEs) are currently utilized in head-up displays (HUDs) as combiner elements. The conventional HUD optics is limited in the field of view and in the display brightness. In some cases the performance of the HUD may be improved by the use of imaging (powered) HOEs. In this paper the basic features of the chromatic aberrations of powered HOEs are reviewed. The chromatic and geometric aberrations of the in-line geometry are discussed in detail. The authors show how to realize this geometry using high efficiency volume holograms. In the in-line geometry the diffraction efficiency of a holographic stack is less than 90. The image is always accompanied by a background of undiffracted light. The use of volume holograms enables the designer to maintain an effective in-line geometry while at the same time the image is separated from the background of undiffracted light. The in-line geometry exhibits the smallest chromatic and geometrical aberrations compared with the off-axis configuration.
A helmet-integrated display (HID) coupled with a microprocessor computer image generator (CIG) provides a low-cost flight-simulation and mission planning/rehearsal system. The proposed HID/CIG training system has a wide 60 deg field-of-view (FOV) display and is lightweight, compact, and transportable. A head tracker linked to the HID permits unlimited head movement and a 360 deg field-of-regard. Two or more HID/CIG systems may be interconnected to simulate interaction with other crew members, aircraft, and ground vehicles.
Combat vehicles of the future may be devoid of direct vision ports but will contain multiple displays creating a virtual environment. The transition from real to virtual can be facilitated by the use of a helmet-mounted display (HMD) that projects a portion of the virtual environment over the real world. The authors propose a simple, light-weight color stereo projection system that has the potential for meeting most of the desired characteristics at a reasonable cost. Imaging is accomplished using CR39 ophthalmic substrates off- axis 15 deg and distorted to correct for astigmatism. The images from two sources are transferred to the focuses by coherent fiber image conduit shaped at one end to minimize field curvature. The demonstrated field of view (FOV) is 15v X 40h deg using readily available image conduit and colored transparencies; maximum FOV is 60v X 90h deg.