Military aviation night vision systems greatly enhance the capability to operate during periods of low illumination. After flying with night vision devices, most aviators are apprehensive about returning to unaided night flight. Current night vision imaging devices allow aviators to fly during ambient light conditions which would be extremely dangerous, if not impossible, with unaided vision. However, the visual input afforded with these devices does not approach that experienced using the unencumbered, unaided eye during periods of daylight illumination. Many visual parameters, e,g., acuity, field-of-view, depth perception, etc., are compromised when night vision devices are used. The inherent characteristics of image intensification based sensors introduce new problems associated with the interpretation of visual information based on different spatial and spectral content from that of unaided vision. In addition, the mounting of these devices onto the helmet is accompanied by concerns of fatigue resulting from increased head supported weight and shift in center-of-gravity. All of these concerns have produced numerous human factors and safety issues relating to thb use of night vision systems. These issues are identified and discussed in terms of their possible effects on user performance and safety.

The presentation traces the development and application of Garrett's Peripheral Vision Display - sometimes known as the Peripheral Vision Horizon Device, or Malcolm Horizon - from the beginning of commercial development to its initial series production and operational application in military aircraft. Problems of reducing a unique, advanced technology concept to standard military practice, and those associated with its flight testing by trained and untrained test pilots, are highlighted. Conclusions with respect to the conduct of the program are drawn and predictions are made regarding the future of such displays.

Future high speed aircraft such as the X-30A, National Aerospace Plane and the 21th Century combat and hypersonic commercial transports will not have a windshield as on current aircraft butt will have the pilot and other flight operating personnel submerged in the fuselage. As a result, in most or all of the flight regimes, the pilot will be guided by vertical and horizontal situation displays on the cockpit instrument panel. Current cockpit instrumentation coupled with computerized flight control systems permit the pilot to perform limited maneuvers such as approach and landing, air intercepts, climbs and cruise. What if the computerized control system fails or is inadequate to perform the complex maneuvers, then the pilot must depend on these situation displays to perform his maneuvers manually. Current electronic primary flight displays are not much larger than conventional instruments and are not precise enough for complex maneuvers. Essentially the subtended angle at the pilot's eye is too small and the resolution of the display too coarse. Previous research on pilot control/display performance in aircraft and in simulators with minimal time delay are examined to attempt to define adequate subtended angle and resolution requirements. Recommendations for cockpit designers based on this research are made and if the existing data is inadequate, additional research is identified. In addition, some hardware technologies are examined which can provide the defined subtended angle of view and resolution.

A prototype near-IR projection system (Patent Pending) was developed by the U.S. Army Research Institute Aviation R&D Activity and the U.S. Army Center for Night Vision and Electro-Optics. The system uses a near-IR cathode ray tube, projection lens, and an optical cut-off filter to project daytime video in the 830-1000nm range of the electromagnetic spectrum, observable only with image intensifier devices. Research is being conducted to determine the system's effectiveness as a supplemental Night Vision Goggle training aid.

The helmet mounted display (HMD) system is designed to facilitate the acquisition of visual information. Instead of requiring gaze shifts to the instrument panel or HUD, specifiable information is available at approximately 0° vertically, and displayed on the helmet visor. Are pilots able to make use of this information without extensive training? If having such information available reduces workload, how does the pilot use the "released" time? To answer these questions, we collected steady state evoked responses (SSEP) to the rapidly flickering display, and also evaluated aspects of visual search as reflected in head and eye movements and eye blinks, in simulated flight. Why these variables are of utility and how they may be used will be described in the context of an evaluation made by our laboratory of the Kaiser HMD system. This was performed for AAMRL/HEA at the McDonnell-Douglas flight simulation facility in St. Louis. Data were collected on B-1 pilots flying "ingress" and "refueling" missions. Although we observed SSEPs in the laboratory, and could record EEG in the electrically noisy simulator environment, several factors prevented a clear demonstration of SSEP under simulation conditions and thus precluded a test of the technique as an index of workload. Specifically, there was less than optimal intensity and waveform of the display, and perhaps most important, there was considerable variablity in the angle of regard of the display due to normal scanning under flight conditions. For purposes of oculographic analysis, the ingress condition was divided into segments associated with approaches to waypoints, threat avoidance, and post-threat periods. Use of the HMD reduced horizontal and vertical visual search activity under all conditions except threat avoidance and post-threat recovery. A second measure, frequency of conjoint occurrence of eye blinks and eye movements, also discriminated the HMD from the nonHMD conditions. Our results suggest that pilots rapidly learn to make effective use of the HMD information, i.e., they spend less time looking at their instrument panels. However, they do not appear to use the "released time" to search their environment more actively.

A near real-time (1 video field delay) digital process has been developed which generates a stereoscopic motion picture from any single, moving imaging sensor. The single sensor three-dimensional imaging technique (SS3D)1 is unique in that it is the first demonstrated to provide binocular 3-D imagery from forward looking sensors, as well as side looking, down looking, and back looking. SS3D is compatible with all existing visually-coupled imaging sensor systems. It may, for instance, transform a 2-D pilotage support system to 3-D with the addition of off-the-shelf video memory and a binocular helmet mounted display. The process is controlled directly by a simple model based on binocular vision requirements and inertial navigation system (INS) outputs. Instead of displaying horizontal parallax only, as generated instantaneously by laterally separated cameras or previous single camera stereoscopic techniques, SS3D displays the full radial complement of disparities generated about the image focus of expansion (or contraction) over a variable time interval as the sensor platform moves, and frees the binocular observer from the normal stereo pair/interocular alignment requirement, making the technology applicable to low-G environments in which viewing alignment may be uncontrollable or continuously variable. Potential applications abound, including pilotage, remote control, visual simulation, surveillance (i.e., a stationary sensor plus SS3D becomes a motion indicator in depth), and entertainment.

One approach to decreasing the size and weight of a helmet-mounted display while maintaining a wide-field-of-view and adequate image resolution is to use a partial binocular-overlap configuration. With a partial binocular-overlap helmet-mounted display the user would see a central binocular image flanked by two monocular images. Properly implemented, the user should not be aware of the partial-overlap condition, but would benefit from the reduced weight, decreased size, and extended field-of-view. However, the successful implementation of a partial-overlap design requires understanding of and solutions for several complex problems.

This paper discusses a system designed to present the viewer with a stereoscopic 240° X 120° visual display that includes 120° binocular overlap. This display is designed to allow the viewer full normal eye scan capabilities and eliminate unwanted optical and kinesthetic clues common to other displays. The use of a display with these capabilities will allow the viewer normal visual perception from a remote site or in a simulated scene - visual telepresence.

A variety of advanced interactive panoramic electro-optic display systems and components have been developed for use with multi-sensory telepresence and simulation systems. The primary purpose of these systems and components is to facilitate recording, image and audio distribution, and display of a scene representing a 360-degree x-y-z cartesian coordinates coverage of a given visual and auditory landscape. A computer graphics generated, a live panoramic camera or prerecorded scene, vehicle electronics data, or a combination of the above may be combined in the displayed scene. Furthermore, each 360-degree scene with x-y-z coverage may be stored on a single frame. Novel panoramic presentation systems, panoramic camera arrangements, and display assemblies are presented. In addition, various interactive and perpherial devices are envisioned for use with the multi-sensory simulation system.

The current trend towards the 'glass cockpit' and 'mission management systems' has certainly increased the data and facilities which are available to the crew but it has also encouraged the crew to devote a significant amount of their attention to 'head down' operations. With the projected complexity of future battlefield scenarios there is an increasing requirement to remain 'head out' and the virtual cockpit is now firmly established as an operational concept for increasing the crew efficiency of future fixed wing and rotary wing aircraft by efficient presentation of information and the flexible configuration of interfacing techniques.

Selective reflection by interference provides laser protection but is angular sensitive and thus the retinal coverage is inherently limited. It can be shown that thin film stacks are similar in function to holograms and rugates. Eye protection requires optimization of angular coverage and spectral bandwidths. These are intimately related and are a function of the available modulation of the indices of refraction. Maximum protection is obtained by designing the filter such that those rays directed toward the center of rotation of the eye are blocked. Practical flight goggles are being manufactured based on these principles.

An advanced optical filter to protect the eye from laser beams is opaque to the entire visible spectrum except for three narrow bands, one in the blue, one in the green, and one in the red. A typical such filter transmits only about 6% of the incident light; yet vision through it is bright and clear and in full natural color.

The success of Liquid Crystal Display (LCD) is recently one of the most important achievements in the flat panel display area. In addition to liquid crystal material improvements, the active matrix (AM) addressing system, prepared by the thin film technology, contributes a great deal to the success of LCDs. This paper identifies three major areas that are critical to the AM system: structure, which includes conventional and novel multilayer devices; material, which covers semiconductors, dielectrics, metals, and organic polymers; and process, which contains unit processes such as deposition, etching, lithography, contact, planarization, self-alignment, and redundant structures. Each of these areas will be critically reviewed and discussed, with emphasis on recent thin film transistor developments.

A new general formalism for finding the optical fields propagating obliquely in layered-inhomogeneous anisotropic media has been obtained and can he used to obtain a general analytic solution for the optical fields in the general inhomogeneous anisotropic media. The results were applied to study the optical properties of general twisted nematic (TN) and supertwisted nematic (STN) liquid crystal displays (LCDs). From the general expression for the field-off state optical transmission for the STN LCDs, we obtained a simple expression for the polarizer orientations, for which the field-off state transmission has an extreme value under parallel or crossed polarizers. For the 180° STN LCDs with parallel polarizers configuration, there are two possible optimized polarizer orientations; one polarizer condition describes the standard 180° STN LCD, and the second polarizer condition describes the black and white 180° optical mode interference (OMI) LCD. However, with crossed polarizers, a new STN geometry with different polarizer arrangement and different optimal conditions from the conventional STN is obtained. The new STN LCD gives a factor of about one-half improvement in both the switching-on and switching-off time constants, and oilers a much improved optical response as compared to the conventional STN LCD.

The performance of a display designed for cockpit applications is discussed. This PIN diode driven active matrix liquid crystal display is capable of operating over a wide temperature range (-40 C to +85 C). It has wide viewing angles (+/-50 H and +15/-30 V), grey scale, and full colors. The resolution is 164 lines per inch. The performance of the display over the whole temperature range is presented. The model of the discrimination index for testing the combined contrast-ratios and colors discrimination was applied for this display. Measurements at different ambient-light levels are presented, both for diffused and specular reflections. Contrast ratios, reflections, and color measurements at different viewing angles are used for discrimination index calculations. The high performance of the display with special surface treatment (front and back) in the cockpit environment is discussed based on those measurements and calculations.

Virtual image and cockpit applications require high resolution, high brightness, high contrast, full color displays with grayscale and which are also lightweight, small in size and have low power consumption. These requirements are well matched to active-matrix liquid-crystal flat-panel displays. In particular, polysilicon active-matrix displays with their high performance and capability for integrated scanners are ideal candidates to satisfy cockpit display requirements. A design analysis is presented for two types of avionic display, a 1-in x 1-in, 1000 x 1000 pixel helmet-mounted display, and a 8-in x 8-in, 1024 x 1024 sub-pixel color cockpit display. The analysis will show that the performance requirements for the display can be met with existing polysilicon device performance and current photolithography equipment. A screen brightness of 75 ft-L can be obtained for the cockpit display, using fluorescent lamp backlighting. Grayscale is obtained through on-plate digital circuitry. The feasibility of many of these concepts has been demonstrated in the design of a 192 x 192 active-matrix array with integrated data and select scanners. The design features of this array, as well as its performance will be presented. The display is capable of showing real-time color NTSC TV signals, with limited grayscale capability. The display operates with a 180 frame/sec refresh rate, while the shift registers operate at speeds up to 2 MHz.

A mathematical model has been developed to predict the color of stroke-written symbology on a color field-sequential CRT display using a Liquid Crystal Shutter (LCS). The model takes into consideration the phosphor, polarizer and LC spectral characteristics, phosphor persistence, and the dynamic response of the LC cell. A software tool was created to evaluate the model and develop a family of color vs. switching parameters curves.

A sunlight readable night vision image system compatible three color display, using a KROMA (Kaiser. Rapid Optical Multi-Color Assembly) filter, has been designed for avionics application. The KROMA display, which uses a "monochrome" CRT and a liquid crystal optical switch, has been optimized for its color, brightness, contrast, and night vision image system compatibility. This approach provides excellent color saturation, high contrast ratio, and low NVIS (Night Vision Image System) radiance, making it attractive for using in night mission aircraft. This paper describes the design considerations in selecting phosphors, color filters, polarizers, and the methods of reducing the ambient light reflection.

Flat fluorescent lamps of 2.6"~12"size for LCD back-lighting have been developed by using hollow cold cathodes. An excellent result is obtained concerning brightness, uniformity of emitted light from lamps and life compared with conventional back-lighting systems.

A typical head-up display (HUD) system incorporates a video camera for recording the HUD symbology and the scene outside the cockpit. When using a HUD video camera (HVC) with a zero-power holographic combiner, the brightness of the HUD symbology seen by the camera changes significantly as a function of vertical field angle because the holographic combiner's reflectance characteristics are angularly sensitive and optimized for the pilot's eye position. A holographic combiner design is presented that overcomes this problem while simultaneously maintaining high reflectance of the phosphor's light to the pilot and high visual transmittance. The combiner contains an additional holographic layer tuned to the blue emission of the P53 phosphor as viewed from the HVC, taking advantage of the HVC's high sensitivity in the blue. The reflectance of the additional hologram is tapered to achieve minimum brightness variation at the HVC. The response of the additional hologram as viewed by the pilot shifts towards the ultra-violet and is thus nearly invisible. Theoretical and measured performance of the combiner are presented.

In geographical areas where low-level nighttime training with high-speed aircraft is restricted, it becomes imperative to employ a vision restriction device (VRD) that simulates nighttime conditions during daytime training. In response to this requirement, a new "bifocal" visor has been designed and evaluated. It consists of spectrally selective filters centered on the eyes, a neutral density lower portion, and is opaque elsewhere. The filters increase the contrast of the navigation forward-looking infrared (FLIR) image projected onto the heads up display (HUD). The neutral density portion allows the pilot to see all displays in full color by simply glancing down. The remainder of the visor is opaque so that the pilot cannot see the outside world and, as such, the visor simulates nighttime conditions. Initial pilot response has been favorable and flight tests are currently underway for evaluation purposes.

Some display technologies (LCD) as well as output 'devices for computer- generated holograms require a binarization of input data. A novel and simple binarization technique is presented and results for image and hologram encoding are discussed. The method introduced is a modification of conventional dither/carrier techniques which allow real-time implementation.However, it avoids the tradeoff between graytone rendition and spatial resolution common to those. Recently the method was applied in display of color images.

There are several current methods for increasing the vertical IFOV of HUD systems, one of which involves the use of a double combiner. A novel approach is described here, utilizing the prismatic magnification of a wedge-shaped combiner, which produces results similar to those of the double combiner. The advantages and disadvantages of this system are discussed.

Dichromated gelatin layers facilitate the design and fabrication of holographic optical elements (HOE) of high efficiency and quality. The research efforts are aimed at the development and evaluation of processes, such as exposure, film development and thermochemical after-treatment, which ensure the attainment of the desired diffraction efficiency, bandwidth and Bragg-shift. The emphasis is placed on the realization of homogeneous diffraction efficiency across the aperture of the HOE. These objectives are achieved by means of a precise control of the thickness of the holographic layer while maintaining simultaneously the capability to modify the refractive index modulation over a wide range. The diffraction efficiencies of transmissive and reflective gratings are unique functions of the state of polarization of the reconstruction wave. The transmissive and the reflective holographic gratings will diffract the perpendicularly polarized component while the parallel component will pass through the hologram without diffraction. Thus, holographic gratings of the transmissive and reflective types can serve as polarizing beamsplitters with an extinction ratio of 1000:1. The experimentally determined diffraction efficiencies show a departure from the predictions of Kogelnik's coupled wave theory.

Extensive research on human vision has led to the emergence of clear design requirements to insure that pilots of combat aircraft can best view new multifunction displays (MFDs). An illuminance profile of an F-16C was conducted by Tektronix, Inc., Beaverton, Oregon supplier of CRTs for the MFD, in an F-16C parked on the runway at General Dynamics, followed by flight tests at 40,000 ft. Human visual requirements (Table I) indicate that a series of tradeoffs must be made in the design of the CRT to optimize display luminance, contrast ratio, color differentiability and symbol legibility. On the ground it was found that only at a narrow angle of incidence can direct sunlight shine on the aircraft MFDs. In flight it was also found difficult to even maneuver the aircraft to a position where direct sunlight shown on the MFD. Even then it was required that the pilot assume an unusual sitting position to allow sunlight to flood the MFD. Based on these ambient illumination tests, it is suggested that the engineering design guidelines for the F-16C cockpit use a value of 5000 foot-candles as a worst-case ambient for the current MFD location, and 7600 foot-candles for worst-case anywhere within the cockpit, to insure maximum avionics display viewability.

An integrated taut shadow mask color CRT has been developed for head down displays in jet fighter and helicopter applications. Completely viewable in fall sunlight ambient environment, this CRT can display high resolution maps and tactical information while withstanding the rugged vibration environment of a military aircraft.