Helmet-mounted Display Research Articles

Head-Up vs. Head-Down: Effects of Precision on Cue Effectiveness and Display Signaling

Two experiments were conducted to investigate the attentional effects in the presentation of cueing symbology with the use of a helmet-mounted display (HMD) relative to a handheld display, and how reduced cue precision (experiment 1) and increased clutter (experiment 2) might modulate these effects. Participants were asked to detect, identify, and give azimuth information for targets hidden in terrain presented in the far domain (i.e., the world) while performing a monitoring task in the near domain (i.e., the display) using either a HMD or hand-held display. The results revealed overall cueing benefits in target detection performance, with slight decrements when cue imprecision was greater than 7.5°. More importantly, undertrust of the cueing data, induced by decreased precision, widened attentional breadth on trials after the automation unexpectedly failed.

Driving with a Head-Slaved Camera System

In a field experiment, we tested the effectiveness of a head-slaved camera system for driving an armoured vehicle under armour. This system consists of a helmet-mounted display (HMD), a headtracker, and a motion platform with two cameras. Subjects performed several driving tasks on paved and in rough terrain, in four conditions: direct view, periscope view, the head-slaved system with normal camera lenses, and with wide-angle lenses. The results showed that performance with direct view was always best, while no benefits of the wide-angle system were revealed. Driving on paved terrain with the HMD system resulted in better longitudinal and lateral vehicle control than with the periscopes for some tasks, although some negative aspects were also observed. This latter finding can be attributed largely to inexperience with the HMD system. Faster track completion times with the HMD system (normal lenses) than with periscope view were observed for driving off the road. These results show that a head-slaved camera system can be an alternative for the periscope system. However, during the first part of the experiment (paved terrain), three of the seven drivers reported symptoms of motion sickness and subsequently stopped with the experiment.

Air–to–ground weapon aiming — a synopsis and a look to the future

SummaryA review of air–to–ground weapon aiming is given, with emphasis placed on the use of the head–up display (HUD), the main cockpit instrument used for accurate weapon aiming over the last 35 years. Nevertheless, the HUD is only of use for the aiming of forward–firing weapons. More advanced weapons have an off–axis capability and their aiming is greatly facilitated by the use of a helmet-mounted sight (HMS) or helmet–mounted display (HMD). The surface–to–air threat and the rules of engagement, particularly in operations other than war, place high demands on the aircrew and the weapon aiming system, both to stand off from the target and to have a high degree of confidence that it is the target. The requirement to perform an accurate in–flight transfer alignment of the weapon places further demands upon the aircrew. Timely and accurate target data, digitally received, plus an on–board targeting system which can automatically search for and recognise a target, are of great utility in the final stages prior to weapon release. The Defence Evaluation and Research Agency is performing research in these areas.

Head-Slaved Tracking in a See-Through HMD: The Effects of a Secondary Visual Monitoring Task on Performance and Workload

Technological advances in helmet-mounted displays (HMDs) have permitted the design of “see-through” displays in which virtual imagery may be superimposed upon real visual environments. The utility of see-through displays in multitask environments remains uncertain, especially in environments that involve switching one's attention between those tasks represented in the virtual display and those existing in the real world. The present study was designed to assess the effects of a secondary visual monitoring task on performance and workload in a head-slaved tracking task. Participants attempted to center a reticle over a moving circular target using a Kaiser Electronics SimEye 2500 HMD while concurrently performing the visual monitoring task component of the Multi-Attribute Task Battery (MATB; Comstock & Arnegard, 1992), which was displayed on a computer monitor. Task difficulty for the head-slaved tracking task was varied by manipulating time delay. Results are discussed in terms of their implications for practical implementation of see-through HMDs in multi-task environments.

Helmet-Mounted Display Symbology for Terrain Avoidance During Low-Level Maneuvers

A simulation study was performed to evaluate helmet-mounted display symbology for fighter aircraft ground collision avoidance systems. Four visual alert symbologies were tested: an iconic cue, an aircraft-fixed (AF) guidance cue, a head-fixed (HF) guidance cue, and an HF guidance cue with a pitch ladder. Participants were given audio and visual side tasks and responded to alerts in different aircraft attitudes. Shorter reaction times were observed when a HF visual alert was given in addition to the standard audio alert. No significant differences in recovery performance (measured by response time and altitude loss) were observed between display formats. However, the display format had a significant effect on participant head motion. With HF guidance cues, pilots were able to perform the recovery maneuver with their heads off axis; with AF guidance cues or no guidance cues, pilots consistently turned their heads to face forward before maneuvering the aircraft.

Study for verification testing of the helmet-mounted display in the Japanese Experimental Module.

Our purpose is to propose a research and development project in the field of telemedicine. The proposed Multimedia Telemedicine Experiment for Extra-Vehicular Activity will entail experiments designed to support astronaut health management during Extra-Vehicular Activity (EVA). Experiments will have relevant applications to the Japanese Experimental Module (JEM) operated by National Space Development Agency of Japan (NASDA) for the International Space Station (ISS). In essence, this is a proposal for verification testing of the Helmet-Mounted Display (HMD), which enables astronauts to verify their own blood pressures and electrocardiograms, and to view a display of instructions from the ground station and listings of work procedures. Specifically, HMD is a device designed to project images and data inside the astronaut's helmet. We consider this R&D proposal to be one of the most suitable projects under consideration in response to NASDA's open invitation calling for medical experiments to be conducted on JEM.

Benefits of color coding weapons symbology for an airborne helmet-mounted display

We assessed the advantages of a color-coded weapons symbology for a helmet-mounted display over monochrome symbology by measuring military pilots' performance while they flew air-to-air combat in a simulator. The pilots fired missiles significantly sooner without sacrificing probability of kill when using the color-coded symbology, demonstrating a substantial practical benefit of color. Actual or potential applications of this work include the design of color codes for helmet-mounted and other displays that use complex symbology to assist performance on cognitively challenging tasks.

Target Cuing in Visual Search: The Effects of Conformality and Display Location on the Allocation of Visual Attention

Two experiments were performed to examine how frame of reference (world-referenced vs. screen-referenced) and target expectancy can modulate the effects of target cuing in directing attention for see-through helmet-mounted displays (HMDs). In the first experiment, the degree of world referencing was varied by the spatial accuracy of the cue; in the second, the degree of world referencing was varied more radically between a world-referenced HMD and a hand-held display. Participants were asked to detect, identify, and give azimuth information for targets hidden in terrain presented in the far domain (i.e., the world) while performing a monitoring task in the near domain (i.e., the display). The results of both experiments revealed a cost-benefit trade-off for cuing such that the presence of cuing aided the target detection task for expected targets but drew attention away from the presence of unexpected targets in the environment. Analyses support the observation that this effect can be mediated by the display: The world-referenced display reduced the cost of cognitive tunneling relative to the screen-referenced display in Experiment 1; this cost was further reduced in Experiment 2 when participants were using a hand-held display. Potential applications of this research include important design guidelines and specifications for automated target recognition systems as well as any terrain-and-targeting display system in which superimposed symbology is included, specifically in assessing the costs and benefits of attentional cuing and the means by which this information is displayed.

The `Outside-In' Attitude Display Concept Revisited

The "outside-in" attitude display concept, which includes a moving-aircraft (as opposed to a moving-horizon) attitude reference, dates back to the early days of flying. The majority of the laboratory and in-flight studies that have evaluated the outside-in format over the years have found it to be superior at preventing roll-reversal errors during normal flying and in recovering from unusual attitudes. Although outside-in attitude displays have been, and continue to be, flown throughout the world, the majority of military and civilian aircraft have failed to adopt this format. This article reviews the purported advantages and disadvantages of outside-in displays, presents a neuropsychological explanation for their general superiority in maintaining spatial orientation, and describes 3 new situations (off-axis helmet-mounted display viewing, global situation displays, and control of uninhabited aerial vehicles) for which the outside-in concept appears to be ideally suited.

Practical Considerations for Fixed Wing Helmet-Mounted Display Symbology Design

Helmet-mounted displays (HMDs) may become a primary source of head-up information in future tactical aircraft. In evaluations, HMDs have produced improved situation awareness and mission performance. To realize this improved performance, HMD equipped pilots spend significantly more time looking off-axis, away from traditional displays. Accordingly, it is important that HMD information be designed so targeting and ownship status symbology is effective and safe. The U. S. Air Force Research Laboratory is working to develop an optimized HMD symbology set. Toward this end, symbol designs must accommodate the conditions of intended use, technology limitations, and integration with other displays. This paper discusses efforts to design target tracking/location and ownship status symbologies for the day/night all weather fixed-wing tactical aircraft application. Design principles derived from both laboratory and flight test are presented. These principles relate to symbology frame of reference, orientation, compression, and line of sight mechanization. Evaluation methodologies are also discussed.

Age-Related Differences in Navigational Performance within an Immersive Virtual Environment

This paper presents an empirical investigation of the effects of aging on spatial performance in an immersive virtual environment. Adults (20 to 75 years of age) were taught a route through a six-room virtual house, while wearing a helmet mounted display (HMD) and using a joystick to navigate the virtual environment. Participants viewed the environment under monoscopic conditions with a display resolution of 640 pixels by 480 pixels, a field-of-view (FOV) of 30° H × 22° V, and a scene update rate of 15 Hz. Participants performed tasks designed to assess their spatial knowledge in terms of landmark knowledge, route knowledge, and configuration knowledge metrics. Locomotion efficiency and landmark knowledge did not significantly change with age. As age increased, route and configuration knowledge significantly decreased while the time needed to complete virtual environment spatial tasks increased (p < 0.05). The occurrence of side effects was also recorded; however, no significant differences with respect to age were found. The results are discussed in terms of designing virtual environments for adults.

Target Cueing in Augmented Reality: A Comparison of Head Mounted with Hand-Held Displays

We conducted a study to examine the effects of target cueing and conformality with a hand-held or head-mounted display to determine their effects on visual search tasks requiring focused and divided attention. Eleven military subjects were asked to detect, identify, and give azimuth information for targets hidden in terrain presented in a simulated far domain environment while performing a monitoring task in the near domain using either a helmet-mounted display or hand-held display. The results showed that the presence of cueing aided the target detection task for expected targets but drew attention away from the presence of unexpected targets in the environment. This effect was mediated by the display used, such that attentional tunneling was reduced when subjects were using the hand-held display.

Feature Detection Performance with Fused Synthetic and Sensor Images

The operational (airborne) Enhanced/Synthetic Vision System will employ a helmet-mounted display with a background synthetic image encompassing a fused inset sensor image. In the present study, three subjects viewed an emulation of a descending flight to a crash site displayed on an SVGA monitor. Independent variables were: 3 fusion algorithms; 3 visibility conditions; 2 sensor conditions; and 9 sensor/synthetic image misregistration conditions. The task was to detect specified terrain features, objects and image anomalies as they became visible in 16 successive fused image snapshots along the flight path. The fusion of synthetic images with corresponding sensor images supported consistent subject performance with the simpler algorithms (averaging and differencing). Performance with the more complex opponent process algorithm was less consistent and more image anomalies were generated. Reductions in synthetic scene resolution did not degrade performance, but elevation source data errors interfered with scene interpretation. These results will be discussed within the context of operational requirements.

Performance Issues in the Design of Helmet-Mounted Displays for Augmented Reality Applications

Performance Issues in the Design of Helmet-Mounted Displays for Augmented Reality Applications

Navigating Large-Scale Virtual Environments: What Differences Occur Between Helmet-Mounted and Desk-Top Displays?

Participants used a helmet-mounted display (HMD) and a desk-top (monitor) display to learn the layouts of two large-scale virtual environments (VEs) through repeated, direct navigational experience. Both VEs were “virtual buildings” containing more than seventy rooms. Participants using the HMD navigated the buildings significantly more quickly and developed a significantly more accurate sense of relative straight-line distance. There was no significant difference between the two types of display in terms of the distance that participants traveled or the mean accuracy of their direction estimates. Behavioral analyses showed that participants took advantage of the natural, head-tracked interface provided by the HMD in ways that included “looking around” more often while traveling through the VEs, and spending less time stationary in the VEs while choosing a direction in which to travel.

Use of Virtual Environments for the Acquisition of Spatial Knowledge: Comparison Among Different Visual Displays

This experiment investigated the effects of three visual display systems differing in immersiveness: A wide field of view (FOV) 3-D helmet-mounted display (HMD); a 3-D HMD with a narrow FOV; and a stationary, rear-projection, wide screen display (WSD). Soldiers explored a virtual environment (VE) representing an actual, unfamiliar heliport. Measures of spatial knowledge of the heliport and presence were recorded. Pretest-posttest differences showed that exploration of the VE transferred to the actual heliport. Visual display had no effect on spatial knowledge of the heliport or on presence. Measures of susceptibility to presence correlated with reported presence only in the WSD condition. Results question popular notions about VEs, which assume that visual-spatial learning is more effective the more immersive the visual display.

Innovative Measures of Accuracy and Situational Awareness during Land Navigation

A helmet-mounted display (HMD)-based computer navigation system that partially mimics the U.S. Army's Land Warrior ensemble provided position information and map updates to soldiers navigating a three-kilometer course. Performance with the HMD system was compared to traditional navigation with paper map, compass, and a hand-held GPS receiver. New objective computer-based measures of navigational accuracy and situational awareness (SA) were developed. Traditional measures of navigational accuracy were not sensitive enough to detect differences between HMD and traditional navigational methods. The more sensitive new measure based on distance traveled found the HMD-based system to be superior. This method is easily adaptable to civilian applications such as orienteering. A supposed advantage of using HMDs is enhanced SA. A SA measure was developed which used probe questions generated by the computer. Although the probe questions found no significant differences between the conditions, the method seems promising for future applications.

Effects of Age and Field-of-Viewon Spatial Learning in an Immersive Virtual Environment

Adults and middle elementary schoolchildren (7-9 years old) were taught a route through a six room virtual house, while wearing a helmet mounted display (HMD) and using a joystick to navigate the virtual environment (VE). Participants viewed the environment under monoscopic conditions with field-of-view (FOV) set at either 30° H × 22° V or 48° H × 36° V. Participants performed tasks designed to assess their spatial knowledge in terms of landmark knowledge, route knowledge, and three configuration knowledge metrics. Landmark knowledge did not significantly change with age or FOV (p > .05). As both age and FOV increased, route and configuration knowledge significantly increased (p < .05). The results are discussed in terms of designing VEs for children.

Conformality and Target Cueing: Presentation of Symbology in Augmented Reality

We conducted a study to examine the issues of frame of reference (world-referenced vs. screen-referenced), target expectancy, target cueing, and viewing condition (i.e., one eye versus two) in the design of see-through helmet mounted displays (HMD) in order to determine their effects on tasks of focused and divided attention. Sixteen subjects (8 civilian, 8 military) were asked to detect, identify, and give azimuth information for targets hidden in terrain presented in the far domain (i.e., the world) while performing a monitoring task in the near domain (i.e., the display). The results showed that the presence of cueing aided the target detection task for expected targets but drew attention away from the presence of unexpected targets in the environment. However, analyses support the observation that this effect can be mediated by the use of world-referenced symbology. Displaying symbology to two eyes produced a very slight benefit for target detection when the target was cued.

Helmet-Mounted Displays And Facial Injury In US Army AH-64A Apache Accidents

There is concern that the helmet display unit (HDU) used by AH-64 Apache helicopter pilots might contribute to facial injury in a crash. The US Army accident database was searched...