This helmet mounted display (HMD) was designed for the extravehicular mobility unit (EMIJ) to be used on the Space Station Freedom. The HMD will be able to display text, graphics, and video to the astronaut. The image will be above his/her normal field of view (FOV) at a comfortable distance. It is believed that this device would be extraordinarily useful in performing scheduled and emergency extravehicular activities (EVAs) . This HMD may be voiceactivated for true "hands-free" operation, without invading the prime work envelope. The Technology Innovation Group (TIG)/Lockheed Engineering and Sciences Company (LESC) holographic HMD was developed for the Crew and Thermal Systems Division and NASA-Johnson Space Center. This HMD is unique because it uses holographic optical elements (HOEs) on the pressure helmet and protective visor surfaces to relay an image from a CRT directly to the eyebox. This HMD provides the user with a biocular virtual image in a 25 degree diagonal FOV, maximum combiner transparency, minimal volume dimension, and an unencumbered working field of view.

A Helmet-Mounted Display (HMD) which utilizes highly efficient trichromatic holographic elements has been designed to support pilot vechicle interface development and human factors studies at the NASA-Langley Research Center. While the optics are fully color corrected, the miniature CRT's are monochromatic. This design provides an upgrade path to full-color when miniature display technology matures to color. The optical design conforms to the helmet shape and provides a 50 degree field-of-view (FOV) to each eye. Built-in adjustments allow each ocular to be independently moved so that the overall horizontal FOV may be varied from 50 degrees to 100 degrees with a corresponding change in the stereo overlap region. The helmet design and interpupillary adjustment allow for the 5th through 95th percentile male and female wearer. Total head-borne weight is approximately 4.2 pounds. The high-resolution monochromatic CRTs are driven by a set of multisync electronics with a maximum video bandwidth of 88 Mhz and supports bith raster and stroke modes. The electronics are designed to be compatiable with the Silicon Graphics IRIS 4D graphics workstations and the ADAGE 340 stroke graphics computer. A Polhemus magnetic tracking device is used to determine the helmet line-of-sight. The helmet will be used to develop innovative new display concepts for the F- 1 8 High-Alpha Research Vehicle (HARV) which make use of the unique display properties of the HMD. Pictorial displays, which convey the appropriate information intuitively, are envisioned. Human factors studies are also planned to evaluate the utility of stereopsis and determine the FOV requirements for different tasks. Concepts proven in the simulator will be carried to flight test in 1993 with a lighter weight, "hardened" version of this HMD design.

Conventional 'straightthrough ' nightvision goggles are now in widespread service with many armed forces throughout the world. Though originally designed for ground forces they have been successfully engineered into the airborne environment and are used on both rotary wing and fixed wing aircraft. However, a major disadvantage in the use of this type of NVG, particularly in fast jet applications, is that they obscure the pilots direct view of the Head Up Display. The combiner eyepiece NVGs solves this problem by giving the pilot a direct view of the HUD and cockpit instruments which is optically combined with the intensified image. The cockpit instruments and HUD are ofcourse compatible with the NVG and are invisible to the NVG. The development ofa Combiner eyepiece NVG from initial concept through to production isdiscussed including design considerations, trade offs and enhancements to the operation of the device. The further development of the combiner eyepiece NVG into a fully integrated ejection safe night vision helmet is also described.

The developtent of three hi4i resolution miniature cRT 's for the He1ut ?'bunted Display Alication is described with reference to the detailed construction. The design considerations for such tubes are discuss1 with reference to the trade offs in terms of display perfonrnce arxI physical parareters . Current state of the art arxi future performance potential is indicated.

This paper presents our efforts to accurately track a Head-Mounted Display (HMD) in a large environment. We review our current benchtop prototype (introduced in {WCF9O]), then describe our plans for building the full-scale system. Both systems use an inside-oui optical tracking scheme, where lateraleffect photodiodes mounted on the user's helmet view flashing infrared beacons placed in the environment. Church's method uses the measured 2D image positions and the known 3D beacon locations to recover the 3D position and orientation of the helmet in real-time. We discuss the implementation and performance of the benchtop prototype. The full-scale system design includes ceiling panels that hold the infrared beacons and a new sensor arrangement of two photodiodes with holographic lenses. In the full-scale system, the user can walk almost anywhere under the grid of ceiling panels, making the working volume nearly as large as the room.

Characteristics of low light level television are being discussed in comparison with night vision goggles, with applications in aircraft and more specific in a helmet mounted vision systein. A brief report is given of investigative work that raust result in an airborne LLLTV with enhanced imaging capabilities under typical operational circunistances.

Helmet mounted displays are exercising the ingenuity of optical and mechanical designers more than any other type of display in attempting to meet essential criteria with currently available technology. The inevitable result is that a wide range of design options and attendant compromises are available to the crew station designer. This paper offers some guidelines on the implications of selecting key helmet display parameters, and describes a unique solution to the problem.

Helicopter pilots prefer for the night-flying tasks a combination of electro-optical sensors with different physical principles in the Infra-Red (IR) and in the near IR spectrum: Thermal Imager (TI or FLIR), Night Vision Goggles (NVG) or Low Light Level Television (LLLTV) . The limits of these three sensors are in extreme darkness with less than 1 mLux illumination or in heavy rain, fog or snow with temperature differences below 0.1 K or with cross-over effects respectively. The development goal for the near future should be an integrated, lightweight helmet h a binocular display on the visor providing two or three sensor images. The paper describes operational requirements, human engineering aspects and the requirements of an integrated light-weight helmet with two NVG-tubes and two CRTs to display superimposed NVG and TI images with flight symbologies.

Providing pilots with direct external visibility may not be possible or desireable in the next generation of aircraft. The drive to increase performance will result in highly swept, low drag forebody designs inconsistent with forward looking windows. Future tactical aircraft may have to enclose pilots in windowless cockpits in order to protect them from threats. Visibility as a design variable is not a new problem, but the solutions of the past have often been brute force approaches that impart significant weight penalties on vehicle design. This paper discusses the design and flight testing of an electronic visibility system concept developed by McDonnell Douglas that provides a low weight, high reliability, flexible alternative approach to providing pilots with external vision.

Advances in electronics, specifically in the area of digital video processing, have opened the door to many new solutions to old problems. Visually coupled systems using Helmet Mounted Displays have been used for years as an aid to pilot vision. These functions are generally accomplished using a helmet display, head tracker and a mechanically gimbaled sensing system. Although this system has proven to be one effective solution in achieving a wide field of regard with a smaller displayed field of view, it has its limitations and drawbacks. A solid state digital gimbaled system has been developed and flight tested as part of a joint study conducted by McDonnell Douglas and the National Aeronautics and Space Administration. This paper will discuss advantages and limitations of digital gimbal systems.

Helmet Mounted Systems (HMS) must be lightweight, balanced and compatible with life support and head protection assemblies. This paper discusses the design of one particular HMS, the GEC Ferranti NITE-OP/NIGHTBIRD aviator's Night Vision Goggle (NVG) developed under contracts to the Ministry of Defence for all three services in the United Kingdom (UK) for Rotary Wing and fast jet aircraft. The existing equipment constraints, safety, human factor and optical performance requirements are discussed before the design solution is presented after consideration of these material and manufacturing options.

Helmet Mounted Systems (HMS) must be lightweight, balanced and compatible with life support and head protection assemblies. This paper discusses the design of one particular HMS, the GEC Ferranti NITE-OP/NIGHTBIRD aviator's Night Vision Goggle (NVG) developed under contracts to the Ministry of Defence for all three services in the United Kingdom (UK) for Rotary Wing and fast jet aircraft. The existing equipment constraints, safety, human factor and optical performance requirements are discussed before the design solution is presented after consideration of these material and manufacturing options.

A study was conducted to compare the performance of AH-64 (Apache) pilots to other Army pilots on visual tasks. Each pilot was given a task presented monocularly to the right eye, a task presented monocularly to the left eye, and a task presented to both eyes simultaneously in a dichoptic task. Results indicated no performance difference between the groups of pilots on the dichoptic task, but indicated better performance on the left monocular task for the AH-64 pilots. These results indicate that AH-64 pilots who are required to switch their attention from their left eyes to their right eyes in order to obtain needed information are capable of processing information efficiently and effectively using only one eye. The implications of these results for the Integrated Helmet and Display Sighting System (IHADSS) are discussed.

A within subjects design was employed to evaluate three factors: dipvergence (.45 to 1 .8 degrees of subtended angle), divergence (.83 to 3.3 degrees), and overlap (35 to 100 percent). Using a configuration composed of a computer graphics engine, two monitors and a two channel optical relay system focused at infinity, imagery simulating FLIR detail and contrast was shown to subjects who searched the field for dynamic alphanumeric and geometric targets. Objective dependent measures were target recognition accuracy and response time. Subjective measures included verbal report of headaches, eyestrain, blurred or double vision any time during experimental trials. Although the extent of misregistration was not statistically significant, a breakpoint in performance was observed for each type of misalignment. Accuracy and latency measures indicated that performance deteriorated significantly as overlap area was decreased. Subjective measures indicated subjects were aware of blurring and doubling as misalignment levels increased and complained of eyestrain when overlap area was decreased.

Five laboratory studies were conducted in order to establish image alignment tolerances for wide field of view monocular/biocular/binocular helmet mounted displays (HMD). Apache Helicopter type production HMD oculars were used by night vision trained pilots in the studies, the results of which underscore the operational advantage of maintaining one dark adapted eye, and quantify the pilots' perceptual sensitivities to display system sources of binocular misalignment.

Independent of the technology used Helmet Mounted Displays in conjunction with Head Tracking Systems (HTS) enable the human operator to pin-point targets by simply looking at them. But HTS accuracy may suffer from a variety of errors inherent with the system which must be considered when aiming at an accuracy of O,l or even better. The HTS set normally consists of - a Display Unit (DU) - a Helmet Mounted Display (HMD) - a Line-of-Sight Locator (LOSL) - a Symbol Generator (SG) Such a system shall have optimum performance while specified as follows: - DU : 800 lines (from 875 Line-Standard) - HMD : wide angle 8O - LOSL : accuracy O.1 What accuracy can be gained when boresighting or additional parallax errors between LOS/HMD and remotely mounted sensors like laser pointer, video or FUR devices are considered? Whereas military boresighting devices may have an accuracy of about O.OO5,standard backsight/foresight aiming by an operator will only reach O.1 due to hand-motion. The latter results in an offset of 5 m when the target is at a distance of 2900 m.

The ability to quantitatively characterize the performance of night vision goggles (NVG) is being investigated because the present method of resolution evaluation relies on an imprecise, subjective pass/fail judgement by a trained observer viewing a test pattern. Variation in an observer's training, experience, psychological state, decision bias and visual acuity strongly affect his or her decision when required to decide if a marginal pair of goggles passes or fails. The controversy concerning the increase in commercial and military helicopter accidents involving NVG indicates a need to determine if 1) the use of defective or marginal NVG is a contributing factor to the increase in accidents or 2) the apparent correlation between NVG and accidents is simply due to the increased use of NVG in an expanded and inherently more dangerous flight envelope. The U.S. Army TMDE Support Group (USATSG) has developed instrumentation to augment the AN/3895 TS test set that presents high and low light level resolution targets to AN/PVS-5, AN/AVS-6 and AN/PVS-7 NVG. The NVG Resolution Augmentation to the AN/3895 TS presented here can also quantitatively measure image quality of other image producing systems which are normally viewed, adjusted or inspected by a human observer. The NVG Resolution Augmentation features a custom electronic circuit which provides a user-friendly interface between a commercially available CCD camera, monitor and oscilloscope. USATSG's Army Primary Standards Laboratory at the Redstone Arsenal is presently studying the possibility of a new measurement service by investigating various CCD camera/lens combinations in order to characterize a machine vision standard observer. A characterized image analysis system would enable absolute as well as relative measurements of image quality.

An account is given of RAE's comprehensive approach to enhancing the capabilities of fast-jets specifically in the air combat role by utilising helmet-mounted equipment. Ground rigs, simulators and aircraft were employed in the development of the devices and their integration with the weapons system. The paper concludes that although ground and simulator trials are a necessary prelude, airborne assessment is essential. By adopting this comprehensive approach to the problem, RAE have established a solid founthtion of experience, covering the design, flight clearance and use of these devices.

The Helmet Mounted Display (HMD) concept has long been regarded as a significant advantage to the modern combat pilot. This concept, however, has been limited to simulators, helicopters, and simplistic display types on fighter aircraft. For the first time, wide field of view HMD5, coupled with a head-steered FLIR, have undergone significant flight tests aboard a state of the art fighter aircraft. This paper discusses some of the lessons learned concerning the use of HMDs in a high performance fighter aircraft.

This paper describes the Virtual Environment Integration Laboratory (VEIL) of the Royal Aerospace Establishment (RAE). The VEIL programme is intended to provoke appropriate technological developments by exploring the human requirements of operating within a virtual cockpit whilst conducting demanding missions. Under construction is a light-weight binocular, colour helmet-mounted display with a wide field of view, driven by a versatile parallelarchitecture computer graphic system which accommodates simulated sensor images from a camera and terrain model. Prototypes of suitable display formats will be developed using a bench-mounted stereoscopic viewing rig which will also facilitate investigation of critical psychophysical issues. The complete VEIL hardware will integrate eye and head position sensors, three dimensional sound, direct voice input, and tactile sensors with the binocular display system. When allied to the ground-attack, helicopter and air-combat simulator facilities of Mission Management Department, it will enable the practicality of operating virtual cockpit systems in a wide variety of missions and tasks to be addressed.

Head movement data were collected from F-15C pilots during simulated air-to-air engagements. The pilots wore helmets fitted with a helmet-mounted display and sight. In the conditions when the display was turned on, pilots viewed flight and weapon information on the display, and used head movements to direct their radar and missiles. In other conditions the display was turned off, and engagements were conducted in the conventional manner. A number of techniques are presented for analyzing and visualizing head movement data. The results of the analysis indicate more head movement with the display turned on, but the results are not statistically significant. It is suggested that this could have been because, despite the display being turned on, pilots still made frequent head movements towards the HUD. There was significantly more head movement during engagements which were conducted within visual range, than those which were commenced beyond visual range. There were also significantly larger displacements and faster movements in azimuth than in elevation. Peak velocities reached 344 degrees/sec in elevation and 60]. degrees/sec in azimuth.

The Harry G. Armstrong Aerospace Medical Research Laboratory (AAMPL) has, since its inception, been chartered to iriprove the Man-Machine Interface (MMI) of Air Force Systems. Included in these systems are man-rwunted systems such as oxygen masks, flight suits, helmets, goggles, etc. It should therefore come as no surprise that AAMRL has been conducting research on Helmet Mounted Displays/Sights (HMD/S) for some time, our Visually Coupled Airborne Systems Simulator (VCASS) being one exaiple. Most of MMRL ' s Helmet Mounted Display (I-MD) research has been targeted toward fighter and attack aircraft including attack helicopters such as the Apache AH-64. HMD design rationale for fighter and attack aircraft is "if you can see the enenrj fi rst , you can shoot them before they shoot you. " This application is adequate for these types of aircraft, but serves no real pirpose for transport or bomber aircraft that have very little or no lethal defensive capability.

Holographic Optical Elements (HOEs) are very appropriate for the construction of Helmet Mounted Displays (HilDs). The low weight and the compactness of HOEs allow for a design which meets the mechanical specifications of a helmet much better than a design with classical optical components. The weight of the optical system can be further reduced by using plastic instead of glass substrates as support material for the holograms. If however, the HOEs are recorded in dichromated gelatin, special precautions have to be taken to obtain humidity-resistant HOEs and to ensure tight adhesion of the gelatin to the plastic. Furthermore, the influence of deformations of the substrate material on the image quality has to be considered as well. In order to find solutions for the above mentioned problems, DCG holograms were recorded on the polycarbonate visor of holographic night vision goggles (HNVG). To study the influence of the optical quality of the plastics on the image quality of the HOEs, various recording configurations have been analyzed.

A drive electronics system for a biocular helmet-mounted display (HMD) is described. The system features microprocessor control with a 1553 interface, raster and stroke graphics multiplexing, image space stabilization, and compensation for pilot head roll. This paper details several video processing functions that have been implemented with mixed-mode integrated circuits including video channel selection and amplification, sync separation, sweep ramp generation, raster and stroke graphics multiplexing, and image space stabilization. Improvements due to use of integrated circuit technology include: circuit card area reduction by a factor of three, power consumption reduction by a factor of four, and an increase in circuit functionality of approximately 50percent.