There are many human factors issues that should be considered when designing a helmet mounted display for use in high speed aircraft with ejection seats. The Joint Helmet Mounted Cueing System Program Office, with support from the Armstrong Laboratory and the Naval Air Warfare Center, has been studying many of these issues and is able to report several findings in the areas of anthropometry, limitations in head movement, helmet stability under high gravity forces and mass properties. This paper serves to summarize the findings of the program office in these areas. The paper will include highlights of several studies that have involved anthropometric data manipulation, 3D head scans, and testing of manikin and human subjects in static and dynamic cockpit environment simulations.

An experiment was conducted to assess the effects of system lag on head tracking performance when positioning a cursor on a stable target. Seven values of lag were tested: 0, 20, 40, 60, 80, 100, and 120 msec. To assess potential interactions, the effects of lag were examined in combination with movement distance and direction. The task was to move a head-tracked cursor to a target that appeared on a six-inch CRT screen in an analog of time and that lag was linearly related to acquisition time, accounting for an increase in target acquisition time of approximately 7 millisecond of lag. Furthermore, the effects of lag on performance were evident with lags as brief as 20 msec.

Military use of unmanned aerial vehicles (UAVs) is gaining importance. Video cameras in these devices are often operated with joysticks and their image is displayed on a CRT. In this experiment, the simulated camera of a simulated UAV was slaved to the operator's head movements and displayed using a helmet mounted display (HMD). The task involved maneuvering a UAV along a winding course marked by tress. The influence of several parameters of the set-up on a set of flight handling characteristics was assessed. To enable variation of FOV and to study the effect of the HMD optics, a simulated HMD consisting of a head slaved window, was projected on a screen. One of the FOVs, generated in this way, corresponded with the FOV of the real HMD, enabling a comparison. The results show that the simulated HMD yields a significantly better performance that the real HMD. Performance with a FOV of 17 degrees is significantly lower than with 34 or 57 degrees. An image lag of 50 ms, typical of pan-and-tilt servo motor systems, has a small but significant influence on steering accuracy. Monocular and stereoscopic presentation did not result in significant performance differences.

The work reported in this paper examines the effect of restricting visual field-of-view (FOV) on rotorcraft pilot head movement. To simulate the FOVs of current and future helmet mounted displays (HMDs) used for night vision pilotage, a FOV restrictor was attached to the helmets of the test subject pilots. The restrictor limited horizontal FOV to 100, 80, 60, 40, and 20 degrees. Ten test subject pilots executed a set of low altitude flight maneuvers in an instrumented NAH-1S helicopter at the NASA Crows' Landing Airfield Head movement was measured with an IR head tracker for those pilots who flew in the rear seat and by a video camera for those who flew in the front seat. Test data indicated that pilots responded to restriction sin horizontal FOV by changing their pattern of head movement, both in azimuth and elevation. These compensation strategies change as FOV decreases and vary from pilot to pilot. Test results reported in this paper, in conjunction with referenced data outlining FOV effects on flight performance, handling qualities, and visual cue ratings, give visionic system designers and users predictive information on pilot workload and performance.

Modern cockpits are some of the most complex systems developed by man. Even relatively simple cockpits require the thoughtful integration of numerous subsystems: structure, controls, avionics, and so on. A review of recent incidents and research shows that modern cockpits have not generally reduced pilot workload during critical flight phases. This has been particularly true as see-through displays were added to existing cockpits. Many such 'add-on' designs are not integrated into the other cockpit systems. Because of the unique characteristics of head-mounted displays, simply duplicating head-down practices will exacerbate any lack of integration. Several cockpit design organizations and their products were also evaluated. Several cockpit display design guides were reviewed and characteristics of good design methodology and philosophy extracted. The keys to a good cockpit design organization are (1) suitable personnel for the team; (2) a structured information requirements study; and (3) early feedback from testing and user evaluation.

The quest for color head- and helmet-mounted displays has led some designers to consider the use of field-sequential color (FSC) because it offers higher resolution than conventional color displays in a compact package. Unfortunately, FSC displays exhibit color breakup sometimes, and the viewing conditions under which this occurs have not been established very well. We performed an experiment to determine color-breakup thresholds for a simple FSC stimulus as a function of stimulus luminance, contrast, and retinal velocity. We developed equations that describe the results and can be used to predict whether color breakup will be visible for specified viewing conditions.

The goals of this research are to measure accuracy and precision of depth perception of 3D objects in se-through head-mounted displays for near-field visualization and to set benchmarks for current technology. In this paper we present results on accuracy and precision of perceived depth for stimuli of various forms presented either in a side by side or in a top-bottom configuration. A finding of these experiment is the unexpected relatively high human subject variability measured which we postulate to be correlated with aspects of the methodology used. Further investigations on methodology related to these types of experiments are being conducted. Finally, we report a new benchmark for the precision of perceived depth of 7 mm.

Modern fighter aircraft windscreens and canopies are typically made of curved, transparent plastic for improved aerodynamics and bird-strike protection. Since they are curved these transparencies often refract light in such a way that a pilot looking through the transparency will see a target in a location other than where it actually is. This effect has been known for many years and methods to correct the aircraft head-up display (HUD) for these angular deviations have been developed and employed. The same problem occurs for helmet-mounted displays (HMDs) used for target acquisition. However, for this application, correction of these errors is more difficult due to the fact the pilot can look through any part of the transparency instead of being constrained to just the forward section as in the case of the HUD. To determine the potential impact of these refractive errors on HMDs six F-15 windscreens and four F-15 canopies were measured from twelve different possible eye positions and a wide range of azimuth and elevation angles. These measurements were then used to develop 'best fit' curves that could be used to partially correct for the refractive effects of the transparencies.

The design of intelligent helmet mounted displays requires addressing what information should be presented and how should that information be presented. This paper presents a systematic approach for identifying what information should be displayed, the context sensitive nature of the information, and context dependent means of deciding how to display the information. This approach incorporates the following features.First, the representation of content separate from the means of display in the information and representation of multiple perspectives of context. Second, the characterization of the display device and the explicit device and the explicit representation of the design problem space for mapping information to display media methods. Third, identification of the worth and cost estimates associated with each information-to-display-method choice. Finally, a mechanism for allocating information to display media methods at both design-time and run-time. The approach provides support for the hierarchical representation of goals using communicative acts, least-commitment constraint posting for display plans, and context sensitive evaluation of worth and cost values used to allocate information to media. This approach also support traceability of design decisions.

This paper will review recent research on attitude symbology on helmet-mounted displays (HMDs) for the air-to-ground mission. General issues concerned with HMDs will be discussed and the lessons learned during the research will be outlined. It is suggested that a sound development approach to HMD symbology is critical since such symbology will constantly follow the pilot's line of sight (LOS). Further, the HMD field-of-view (FOV) is likely to be limited. Hence, if HMDs are to be used operationally for more than weapon aiming a number of human factors issues need to be investigated, such as the optimal method of presenting attitude information. The pitch ladder was designed to be presented along the boresight, directly in the pilot's LOS, at a fixed frame of reference. As pilots are used to and have been trained upon attitude information presented in consistency with the forward LOS, information representative of the pitch ladder may be beneficial on HMDs. None the less, since the pitch ladder was not designed for the HMD, novel formats may be more appropriate. As with all novel attitude symbology, enhanced operational performance must always be demonstrated and substantiated against the conventional existing symbology. Several experiments will be described which compared the pitch ladder to novel symbology, namely: the cylinder display; the arc segmented attitude reference display; and the modified roll-pitch display. These experiments were conducted using a variety of operationally relevant mission tasks and scenarios. The results will be summarized and the lessons learned for prototyping attitude symbology on HMDs will be discussed.

A methodology for developing helmet-mounted display (HMD) symbology from conception to flight is being developed within the Defence Evaluation and Research Agency (DERA). As part of this development, experiments have been undertaken to evaluate target locator cues (TLCs). A TLC is designed to represent the direction and angular distance from the pilot's line-of-sight outside the HMD FOV. A previous study by Geiselman and Tsou identified three potentially effective TLCs which were used in these experiments. The first experiment was conducted on the DERA fused imagery simulation testbed (FIST). FIST is a simulation facility which projects images on a large curved screen to simulate HMD and HUD symbology. A 10 degree simulated FOV was used for the HMD symbology. The results showed two of the TLCs to be significantly better than the third. The experiment was repeated using the Viper II helmet used. The result were very similar to those obtained in the first experiment, helping to validate the use of low fidelity simulation in symbology development.

Miniature image sources are now appearing in a variety of technologies that have the potential for application to military head mounted displays. These technologies take the form of emissive, transmissive, reflective, and scanning display configurations. Each of these technologies have particular characteristics that make them attractive for use in head mounted display systems. The diversity of military applications result in varying set of requirements that must be considered during the image source selection process. However, initial selection of a new technology for head mounted applications involves the evaluation of a few basic characteristics. A candidate technology should be adaptable to either direct-view or see-through display systems and have an appropriate size, resolution, luminance, and required power.

A number of programs are attempting to validate the advantages and disadvantages of miniature flat panel displays compared to CRTs for use in rotary wing helmet mounted displays. This paper will explore the unique requirements of rotary wing helmet mounted displays and will assess the applicability of miniature flat panel displays for meeting these requirements. Remaining technical challenges will be discussed and potential solutions identified.

The Litton Soldier Vision Sub-system is a lightweight, low power, display system that can be mounted on the soft cap, helmet or bare head, of a soldier in the field. The head mounting approach allows hands-free operation by the soldier, thereby providing the ability to run stand shoot while still being able to observe the computer's display. Likewise, command post staff, maintenance technicians, even firemen, can function in a similar manner. The system contains four major components: HMD, electronics unit, battery housing, and cables. The HMD is a folded path design using a 60 hertz refresh active matrix liquid crystal display, with backlight from an array of six light-emitting diodes. The typical power source is a nominal 9 VDC lithium battery, the BA-5600, but rechargeable batteries can also be used. Extensive design effort has been expended to add the shielding and filters necessary for unimpaired operation in close proximity to tactical radios. The entire system, including battery and cables, weighs approximately 2.3 pounds. Small size, low power, and light weight allow the system to be used in many varied applications, including display of maintenance manuals, remote medical assistance, and field reconnaissance.

The Maintenance and Repair Support System (MARSS) is a new, revolutionary platform for mobile computing and communications designed for the soldier operating on the digital battlefield of the future. MARSS is the first major research and development program that addresses the issues of mounting mobile computing apparatus directly onto the human body and represents an important leap forward toward hands free man-machine interface. The goal of the program was to develop a system capable of workstation level performance in a package that fits comfortably with the human body and enhances the user's ability to perform complex tasks that would otherwise require extensive learning and time to accomplish. The MARSS system uses advanced micro-optical displays such as the active matrix electroluminescent image source for near real time video display across a spectrum of rugged technology that can benefit both military and commercial users. The MARSS effort is a Defense Advanced Research Projects Agency program in collaboration with the US Army Soldier Systems Command (SSCOM) executed by McDonnell Douglas under SSCOM contract number DAAK60-95-C2029.

The first ever deployed arthroscopic knee surgeries have been performed using a high resolution color head-mounted display (HMD) developed under the DARPA Advanced Flat Panel HMD program. THese procedures and several fixed hospital procedures have allowed both the system designers and surgeons to gain new insight into the use of a HMD for medical procedures in both community and combat support hospitals scenarios. The surgeons demonstrated and reported improved head-body orientation and awareness while using the HMD and reported several advantages and disadvantages of the HMD as compared to traditional CRT monitor viewing of the arthroscopic video images. The surgeries, the surgeon's comments, and a human factors overview of HMDs for Army surgical applications are discussed here.

The development of a head mounted display concealed within eyeglasses has been a long term objective of many head mounted display (HMD) development efforts. This paper will review design concepts from the literature, with a view toward assessing the practical merits of the various approaches. The factors of importance in miniaturizing a HMD will be summarized. Finally, we will briefly summarize some new approaches including the use of alternative display technology that may lead to a display system hidden within eyeglasses frames.

MicroDisplay devices are based on a combination of technologies ranging from the extreme integration capability of conventionally fabricated CMOS active-matrix liquid crystal display substrates to proprietary tunable color- filter technology, to optical distortion correction technology for lens-system compensation. All of these technologies were devised to create a line of application- specific integrated circuit single-chip display devices with integrated computing, memory, and communication circuitry. Next-generation portable communication, computer, and consumer electronic devices such as truly portable monitor and TV projectors, eyeglass-clip-on virtual displays, pagers and personal communication services hand-sets, and wristwatch-mounted video phones are all target markets for MicroDisplay technology.

FFV Aerotech has for the past ten years been studying different types of HMS for fixed-wing applications. In 1992 was the first flight trial performed with a LED-reticle generator. FFV has then made a second prototype system called ODEN.

Pilkington Optronics have developed a range of display helmets for airborne use. Comprising both monocular and binocular systems, the 'Guardian' range is aimed at helicopter and fixed wing aircraft. Pilkington Optronics has teamed with Kentron in South Africa to exploit their respective helmet technologies and to penetrate the display helmet market place. A number of key technologies have enabled the development of competitive systems. A half inch CRT has been developed which provides high brightness, high resolution and low weight. This coupled with advances in visor coating technologies has allowed a HMD system to be developed which leads the market. A headtracker developed by Kentron is an optical system and has undergone extensive flight trials in both helicopter and fast jet. It offers excellent installed accuracy an extensive headbox and has a number of key features which make it attractive to the end user.

The Advanced Helicopter Pilotage (AHP) program is developing a wide field-of-view, night and adverse weather vision system for helicopter navigation and obstacle avoidance. THe AHP hardware consists of a second generation thermal sensor, a high definition image intensified camera, and a helmet mounted display (HMD). The specifications for next generation night vision sensor require through the system performance measures. As such, particular importance is given to the quantification of limiting resolution at operationally relevant illumination levels rather than measures performed under typical laboratory illumination.In this paper, descriptions of the AHP HMD and image intensified camera are given, and the measured modulation transfer function of the HMD is reported. Also covered are the results of noise limited resolution testing of the AHP HMD and image intensified camera. A comparison of MTF and noise limited resolution measures, made under the appropriate illumination, using a Dage HR-2000 is presented.

In 1973, the Development of the Army adopted night vision devices for use in aviation. Known as the AN/PVS-5 night vision goggle (NVG), these devices, which are based on the principle of image intensification (I²), have become the mainstay for the aviator's capability to operate during periods of low illumination, i.e., at night. In the 2 years that have followed, a number of engineering the advancements have improved greatly the performance of these devices. The current version, using third generation I² technology, is known as the Aviator's Night Vision Imaging Systems (ANVIS). The performances histories of NVGs and ANVIS are presented with an emphasis on visual and biodynamic issues which have, and do, affect aviator mission effectiveness and safety.

A preliminary study was conducted to investigate the use of visual flow cues as an aid to ground and vertical drift awareness during helicopter flight and targeting while using night vision goggles (NVGs). Three displays wee compared: (1) NVG display: simulated NVG image of cockpit and external environment. (2) Overlay display: NVG image with an overlay display but with symbology flow cue field and a surrounding wire-frame globe; (3) Cut-out display: same as the overlay display but with symbology removed from the central region. Three levels of contrast were also compared using each display type. The visual scenery was displayed to subjects using a helmet-mounted virtual reality device that had a 40 by 50 degree field-of-view liquid crystal display. The study involved six pilots. Three tasks were given: (1) Search task: designate enemy targets with a helmet-mounted sight; (2) Hover task: null out all transnational and yaw rates while in a hover; (3) Search/Hover task: perform both Search and Hover tasks simultaneously. These tasks were conducted in a fixed-based helicopter simulator which used the dynamics of a small-scale model helicopter. The following performance measures were collected: (1) Pilot ability to detect and recognize targets; (2) Pilots ability to null transnational and yaw rates; (3) Time scanning the instrument panel. Subjects also rated displays for efficacy in completing the three tasks. Target detection scores conducted during the Search and Search/Hover tasks were highest using the NVG display, followed by the cut-out display. Root-mean-square (RMS) drift rate error was comparable for all display types in the Hover and Hover/Search tasks, however RMS control input activity in all the translational axes was significantly higher in both rate-cueing displays than with the NVG display. From the control input and drift rate time histories it appears that the motion cues were more compelling in the overlay and cut- out displays than those perceived in the NVG display. A significant decrease in instrument-scanning time was observed for both the overlay and cut-out displays compared to the NVG display, with pilots flying essentially head-out- of-cockpit while using the rate-cueing displays. Contrast was not observed to have a significant effect on hover performance in any of the displays.

Wright Laboratory's Variable-Stability In-Flight Simulator Test Aircraft (VISTA) NF-16D is the newest in-flight simulator in the USAF inventory. A unique research aircraft, it will perform a multitude of missions: to develop and evaluate flight characteristics of new aircraft that have not yet flown, and perform research in the areas of flying qualities, flight control design, pilot-vehicle interface, weapons and avionics integration, and to train new test pilots. The VISTA upgrade will enhance the simulation fidelity and research capabilities by adding a programmable helmet-mounted display (HMD) and head-up display (HUD) in the front cockpit. The programmable HMD consists of a GEC- Marconi Avionics Viper II Helmet-Mounted Optics Module integrated with a modified Helmet Integrated Systems Limited HGU-86/P helmet, the Honeywell Advanced Metal Tolerant tracker, and a GEC-Mounted Tolerant tracker, and a GEC- Marconi Avionics Programmable Display Generator. This system will provide a real-time programmable HUD and monocular stroke capable HMD in the front cockpit. The HMD system is designed for growth to stroke-on-video, binocular capability. This paper examines some of issues associated with current HMD development, and explains the value of rapid prototyping or 'quick-look' flight testing on the VISTA NF-16D. A brief overview of the VISTA NF-16D and the hardware and software modifications made to incorporate the programmable display system is give, as well as a review of several key decisions that were made in the programmable display system implementation. The system's capabilities and what they mean to potential users and designers are presented, particularly for pilot-vehicle interface research.

The National Research Council (NRC) of Canada, in conjunction with the Canadian Department of National Defence, is investigating the use of helmet-mounted displays as an aid in improving pilot situational awareness in all- weather search and rescue helicopter operations. For over 30 years, the NRC Bell 205 Airborne Simulator has been an integral part of valuable research programs. Equipped with a full authority fly-by-wire control systems, the Bell 205 has variable stability characteristics, which makes the airborne simulator the ideal platform for the integrated flight testing of helmet-mounted displays in a simulated operational environment. This paper will describe the test facility in detail, including a description of the airborne simulator, the fiber-optic helmet-mounted display hardware, the camera system, the head tracking system, and the sensor platform. In addition, the paper will provide a complete description of the symbology overlaid on the camera image that was developed for use with the helmet mounted display. The paper will conclude with the description of a planned preliminary handling-qualities investigation into the effects of using helmet-mounted displays on the pilot's workload and performance while performing standard maneuvers.

The Integrated Helmet Audio-Visual System (IHAVS) project was originated and funded by the JSF Cockpit and Aircrew Systems Integrated Product Team, a joint service sub-team of the JSF Flight Systems IPT. The IHAVS project was conceived as a short-duration technology maturation and flight demonstration program. The JSF Flight Systems IPT provided overall project management, funding, and leadership throughout the entire integration and demonstration effort. The IHAVS project integrated head-mounted aural, verbal, and visual cockpit technologies, previously demonstrated individually, into a single synergistic system in a TAV-8B. A 25-event test operation was conducted to demonstrate the utility of this advanced integrated human systems interface for performing strike missions. IHAVS technologies included a GEC Viper II HMD system, a Polhemus helmet tracker, an Armstrong Laboratory 3-D audio system with ANR, a Smiths Industries IVM, and an LMA NITE Hawk SC TPOD. Three test pilots, one each from the Marine Corps, Air Force, and Navy, were selected to fly similar flight events.

An interactive system for disabled's is shown. The interactive system uses the head position as communication mean. The systems uses an IR light source to have the relative or absolute position over the work frame. In the work frame an interactive software was made in the Windows platform to active and modify appliances.

The VISTA/NV-16D is currently the newest in-flight simulator in the USAF inventory. This unique research aircraft will be fitted with the GEC-Marconi Avionics Programmable Display System. This equipment provides the capability to rapidly develop display concepts on both helmet-mounted display and head up displays in a dynamic flight test environment. The equipment provided includes an enhanced Viper II Helmet Mounted Display fitted to the HGU-86/P helmet. Display drive is provided by a very capable graphics generation system which also provides display drive to the standard F-16 Head Up Display. The system provides real time reprogrammable stroke and stroke on raster symbology on the HUD and on the HMD. The system is initially configured with monocular Stroke only HMD drive, but growth to dual HMD, stroke on video and binocular HMDs is available. The Honeywell Advanced Metal Tolerant Helmet Tracker System is integrated within the HMD Programmable Display System providing very accurate helmet orientation information to the graphics generator which is used for the display of space stabilized symbology when required. A fail safe backup display generator provides reversionary display on the HUD. This paper provides a detailed description of this equipment and also address some of the design techniques involved in developing this high performance system.

This novel flight instrument display presents information to the pilot in a simple and easily comprehensible format by integrating the five orientational flight parameters. It allows the pilot to select specific orientation parameters and then follow a simple tracking task which ensures that these parameters are maintained or, if necessary, recovered. The pilot can at any time check any parameter he wishes, but is free from the requirement to continually sample and combine information from the traditional instruments to maintain stable flight. Cognitive workload to maintain orientation is thus reduced. Our assessment of the display in a UH-60 helicopter simulator showed that the novel display makes recovery from unusual aircraft attitudes and instrument flying easier than when using the standard instrument panel.

In 1995 the UK Defence Evaluation and Research Agency conducted a series of pilotage field of view (FOV) trials on a Lynx helicopter. These were performed under the auspices of the Technical Cooperation Program, subgroup H, Technical Panel 6. Before the commencement of the trials it was clear that it would be necessary to have available an objective method of determining not only the accuracy with which the various trial mission task elements would be flown, but also the relevance of the flying accuracy to the operational application. Such an objective method was not known to exist, therefore a suitable technique was derived, and deliberately tailored to give some read-across to the widely accepted subjective Cooper-Harper handling qualities rating. The derivation, application and usefulness of the composite objective rating technique are described herein, together with a synopsis of the trials themselves. The paper concludes with a summary of the trials results to date, which indicate a relationship between both objectively- and subjectively-gathered data concerning the flying performance, and the FOV of the evaluation pilot.

HMDs have severe demands on luminance and resolution. There is a requirement to view the display over a range of ambient illumination from full sunlight to night and to provide high accuracy for weapon release. Installation constraints further complicate the optical design and mass is crucial for the head mounted hardware. Currently the only display device that can met these demands is the monochrome cathode ray tube (CRT). This paper explores the potential for replacing the CRT. THe problem areas such as installation, illumination and drive are discussed and the suitability of various technologies is considered. The potential for color is also reviewed.