Task performance in a head-mounted display: The impacts of varying latency

The purpose of this study was to determine how latency in a head-mounted display (HMD) affects human performance. Virtual environments (VEs) are used frequently for training. However, VEs can cause simulator sickness. Prior work in our laboratory has examined the role of varying latency in simulator sickness. However, the effect of varying latency on task performance has not been examined. Subjects participated in a repeated measures study where they were exposed to two different latency conditions in an HMD: constant (70 ms) and varying (70–270 ms). During each HMD exposure, subjects used a laser pointer to repeatedly “shoot” at laser targets while accuracy and time-to-hit were recorded. Subjects scored fewer hits and took longer to hit targets in the varying latency condition. These findings indicate that individuals exposed to varying latency perform worse than individuals exposed to a lower constant latency.     

The effects of 0.2 Hz varying latency with 20–100 ms varying amplitude on simulator sickness in a helmet mounted display

The relationship between the occurrence of simulator sickness (SS) and varying latency in a helmet-mounted display (HMD) was explored in this study. Previous work has always considered latency to be a constant. The aim of this research was to determine if a latency that varied over time would impact the experience of SS for HMD users. An object location task was used while viewing real, live video scenes via HMD. A planned comparisons approach was utilized with four experimental conditions, 2 of them having constant latency (0 ms added to system baseline, 200 ms added to system baseline) and 2 of them having sinusoidally varying latency (100 ms amplitude at 0.2 Hz frequency, and 20–100 ms varying amplitude at 0.2 Hz frequency). These conditions allowed for the assessment of the effects of constant latency vs. varying latency on the experience of SS. The results indicated that a varying latency is associated with greater experience of SS among HMD users than constant latency. Results also indicated, as has other recent research, that added constant latency on its own does not appear to be associated with the experience of higher levels of SS in an HMD.     

Effect of VR technology matureness on VR sickness

In this paper relationship of perceived virtual reality (VR) sickness phenomenon with different generations of virtual reality head mounted displays (VR HMD) is presented. Action content type omnidirectional video clip was watched by means of four HMDs of different levels of technological matureness, with a 2D monitor used as a reference point. In addition to subjective estimation of VR sickness effects by means of the SSQ questionnaire, psychophysiology of the participants was monitored. Participant’s electrodermal activity, heart rate, skin temperature and respiration rate were measured. Results of the study indicate differences between HMDs in both SSQ score and changes of physiology. Skin conductance was found to be significantly correlated with VR sickness. Mobile HMD did not induce significantly higher levels of VR sickness. Disorientation SSQ was proven to be a useful tool for assessing the VR sickness effects.

     

Sensitivity to visual speed modulation in head-mounted displays depends on fixation

A primary cause of simulator sickness in head-mounted displays (HMDs) is conflict between the visual scene displayed to the user and the visual scene expected by the brain when the user’s head is in motion. It is useful to measure perceptual sensitivity to visual speed modulation in HMDs because conditions that minimize this sensitivity may prove less likely to elicit simulator sickness. In prior research, we measured sensitivity to visual gain modulation during slow, passive, full-body yaw rotations and observed that sensitivity was reduced when subjects fixated a head-fixed target compared with when they fixated a scene-fixed target. In the current study, we investigated whether this pattern of results persists when (1) movements are faster, active head turns, and (2) visual stimuli are presented on an HMD rather than on a monitor. Subjects wore an Oculus Rift CV1 HMD and viewed a 3D scene of white points on a black background. On each trial, subjects moved their head from a central position to face a 15° eccentric target. During the head movement they fixated a point that was either head-fixed or scene-fixed, depending on condition. They then reported if the visual scene motion was too fast or too slow. Visual speed on subsequent trials was modulated according to a staircase procedure to find the speed increment that was just noticeable. Sensitivity to speed modulation during active head movement was reduced during head-fixed fixation, similar to what we observed during passive whole-body rotation. We conclude that fixation of a head-fixed target is an effective way to reduce sensitivity to visual speed modulation in HMDs, and may also be an effective strategy to reduce susceptibility to simulator sickness.     

Vection and cybersickness generated by head-and-display motion in the Oculus Rift

Cybersickness is often experienced when viewing virtual environments through head-mounted displays (HMDs). This study examined whether vection (i.e., illusory self-motion) and mismatches between perceived and physical head motions contribute to such adverse experiences. Observers made oscillatory yaw head rotations while viewing stereoscopic optic flow through an Oculus Rift HMD. Vection and cybersickness were measured under 3 conditions of visual compensation for physical head movements: “compensated”, “uncompensated”, and “inversely compensated”. When a nearer aperture was simulated by the HMD, vection was found to be strongest in the “compensated” condition and weakest in the “inversely compensated” condition. However, vection was similar for all 3 conditions during full-field exposures. Cybersickness was most severe for the “inversely compensated” condition, but was not different for the other two conditions. We conclude that mismatches between perceived and physical head-movements can contribute strongly to cybersickness. The relationship between vection and cybersickness is weaker and appears complex.     

Subjective and objective evaluation of visual fatigue caused by continuous and discontinuous use of HMDs

During continuous use of displays, a short rest can relax users' eyes and relieve visual fatigue. As one of the most important devices of virtual reality, head‐mounted displays (HMDs) can create an immersive 3D virtual world. When users have a short rest during the using of HMDs, they will experience a transition from virtual world to real world. In order to investigate how this change affects users' eye condition, we designed a 2 × 2 experiment to explore the effects of short rest during continuous using of HMDs and compared the results with those of 2D displays. The Visual Fatigue Scale, critical flicker frequency, visual acuity, pupillary diameter, and accommodation response of 80 participants were measured to assess the subject's performance. The experimental results indicated that a short rest during the using of 2D displays could significantly reduce users' visual fatigue. However, the experimental results of using HMDs showed that short rest during continuous using of HMD induced more severe symptoms of subjectively visual discomfort, but reduced the objectively visual fatigue.     

Depth of focus and visual recognition of imagery presented on simultaneously viewed displays: implications for head-mounted displays

OBJECTIVE: We sought to determine the optimal focal distance for a semitransparent monocular head-mounted display (HMD) integrated with a flight simulator display and to investigate whether observers experienced visual discomfort or impaired target recognition when using an HMD set at the optimal distance. BACKGROUND: When an observer wears a monocular HMD and views a simulator display, focal distances of both displays must be within the observers' depth of focus to prevent blurred imagery. Because focal distance can vary by as much as 0.5 m in U.S. Air Force multifaceted simulator displays, we determined whether a monocular HMD could be integrated with a simulator display without blurred imagery or discomfort. METHOD: Depth of focus and visual recognition were measured with a staircase procedure, and visual discomfort was measured with a questionnaire. RESULTS: Depth of focus was 0.64 diopters in one condition tested, but it was affected by luminance level and display resolution. It was recommended that HMD focal distance equal the optical midpoint of the range of viewing distances encountered in the simulator. Moreover, wearing an HMD produced a decline in recognition performance for targets presented on the simulator display despite both displays being within observers' depth of focus and producing no visual discomfort. CONCLUSION: Monocular HMDs can be integrated with multifaceted simulator displays without blurred imagery or visual discomfort, provided that the correct focal distance is adopted. APPLICATION: For situations involving simultaneously viewed visual displays.     

Allocating less attention to central vision during vection is correlated with less motion sickness

Visually induced motion sickness (VIMS) is a common discomfort response associated with vection-provoking stimuli. It has been suggested that susceptibility to VIMS depends on the ability to regulate visual performance during vection. To test this, 29 participants, with VIMS susceptibility assessed by Motion Sickness Susceptibility Questionnaire, were recruited to undergo three series of sustained attention to response tests (SARTs) while watching dot pattern stimuli known to provoke roll-vection. In general, SARTs performance was impaired in the central visual field (CVF), but improved in peripheral visual field (PVF), suggesting the reallocation of attention during vection. Moreover, VIMS susceptibility was negatively correlated with the effect sizes, suggesting that participants who were less susceptible to VIMS showed better performance in attention re-allocation. Finally, when trained to re-allocation attention from the CVF to the PVF, participants experienced more stable vection. Findings provide a better understanding of VIMS and shed light on possible preventive measures.

Practitioner Summary: Allocating less visual attention to central visual field during visual motion stimulation is associated with stronger vection and higher resistance to motion sickness. Virtual reality application designers may utilise the location of visual tasks to strengthen and stabilise vection, while reducing the potential of visually induced motion sickness.     

Exploratory factor analysis and validity of the virtual reality symptom questionnaire and computer use survey

Abstract

The widespread use of virtual reality head-mounted-displays (HMDs) calls for a re-examination of the impact of prolonged exposure to fixed visual displays at close ocular proximity. The purpose of this study is to validate the Virtual Reality Symptoms Questionnaire (VRSQ), created to understand symptoms of prolonged HMDs use, and Computer Use Survey (CUS), created to assess general physical and visual discomfort symptoms. Participants (N?=?100) recorded their general discomfort symptoms using the CUS, performed an interactive task using a HMD for thirty minutes, and then answered the CUS again along with the VRSQ. VRSQ, analysed using an exploratory factor analysis, indicated a clear two-factor solution, and demonstrated very good internal consistency (α?=?0.873). The CUS, also analysed using an exploratory factor analysis, indicated a four-factor solution, and demonstrated good internal consistency (α?=?0.838).

Practitioner Summary: A quantitative-experimental study was conducted to explore the factor structure and validate both the Virtual Reality Symptoms Questionnaire (VRSQ), and the Computer Use Survey (CUS). Findings indicate the VRSQ and CUS are precise and accurate survey instruments for evaluating discomfort after VR-HMD use and the latter for computer use.

Abbreviations: VRSQ: virtual reality symptom questionnaire; CUS: computer use survey; OLED: organic light-emitting diode; MSQ: pensacola motion symptom questionnaire; SSQ: simulator sickness questionnaire; 3?D: three-dimensional computer generated space; VR: virtual reality; VR-HMD: virtual reality head-mounted-display; HMDs: head-mounted-displays; EFA: exploratory factor analysis     

The influence of different electronic maps and displays on performance and operator state in a geographic orientation task

Mobile electronic displays for geographic orientation and navigation are used increasingly in various civil and military domains. But it is still unclear which displays and kinds of map presentation suit best for specific purposes. In the present experiment, a head-mounted display (HMD) and a display from a personal digital assistant (PDA) were compared in a simulated geographic orientation task in an urban environment. Furthermore, the effect of three kinds of map presentation (egocentric, geocentric and geocentric with colour cues) was analysed. The simulated orientation task was projected on a screen and participants controlled their locomotion within the urban area by means of a joystick. Task completion time, peripheral attention, workload, fatigue and simulator sickness were registered as dependent variables. In comparison to the geocentric map the egocentric map showed a significant shorter task completion time and the geocentric map with colour cues a significant higher peripheral attention. Task completion time of the HMD and the PDA did not differ significantly. However, peripheral attention and most indices of workload, fatigue and simulator sickness were significantly better for the PDA. Therefore, the results recommend to apply PDAs and egocentric maps for comparable orientation tasks.     

Inhibition-related N2 and P3: Indicators of visually induced motion sickness (VIMS)

Visually induced motion sickness (VIMS) leads to psychophysiological discomfort and has an adverse effect on executive function. Response inhibition, which can inhibit inappropriate behavior to adapt to changing environments, is an important aspect of executive function. The present study investigated the changes in response inhibition following VIMS using event-related potentials (ERPs). In a two-choice oddball task, ERPs were recorded at baseline (pretest) and after a 40-min virtual reality (VR) training session (posttest). The results showed a larger deviant-N2 amplitude, smaller deviant-P3 amplitude and delayed deviant-P3 latency after the VR training. Our findings suggest that VIMS is characterized in part by impaired response inhibition and that inhibition-related N2 and P3 can be used as electrophysiological indices of response inhibition in the assessment of VIMS.     

Perceived orientation in physical and virtual environments: changes in perceived orientation as a function of idiothetic information available

Two experiments examined perceived spatial orientation in a small environment as a function of experiencing that environment under three conditions: real-world, desktop-display (DD), and head-mounted display (HMD). Across the three conditions, participants acquired two targets located on a perimeter surrounding them, and attempted to remember the relative locations of the targets. Subsequently, participants were tested on how accurately and consistently they could point in the remembered direction of a previously seen target. Results showed that participants were significantly more consistent in the real-world and HMD conditions than in the DD condition. Further, it is shown that the advantages observed in the HMD and real-world conditions were not simply due to nonspatial response strategies. These results suggest that the additional idiothetic information afforded in the real-world and HMD conditions is useful for orientation purposes in our presented task domain. Our results are relevant to interface design issues concerning tasks that require spatial search, navigation, and visualization.     

Interactive gaming reduces experimental pain with or without a head mounted display

While virtual reality environments have been shown to reduce pain, the precise mechanism that produces the pain attenuating effect has not been established. It has been suggested that it may be the ability to command attentional resources with the use of head mounted displays (HMDs) or the interactivity of the environment. Two experiments compared participants’ pain ratings to high and low levels of electrical stimulation while engaging in interactive gaming with an HMD. In the first, gaming with the HMD was compared to a positive emotion induction condition; and in the second experiment the HMD was compared to a condition in which the game was projected onto a wall. Interactive gaming significantly reduced numerical ratings of painful stimuli when compared to the baseline and affect condition. However, when the two gaming conditions were directly compared, they equally reduced participants’ pain ratings. These data are consistent with past research showing that interactive gaming can attenuate experimentally induced pain and its effects are comparable whether presented in a head mounted display or projected on a wall.     

Light-field head-mounted displays reduce the visual effort: A user study

Head-mounted displays (HMDs) allow the visualization of virtual content and the change of view perspectives in a virtual reality (VR). Besides entertainment purposes, such displays also find application in augmented reality, VR training, or tele-robotic systems. The quality of visual feedback plays a key role for the interaction performance in such setups. In the last years, high-end computers and displays led to the reduction of simulator sickness regarding nausea symptoms, while new visualization technologies are required to further reduce oculomotor and disorientation symptoms. The so-called vergence–accommodation conflict (VAC) in standard stereoscopic displays prevents intense use of 3D displays, so far. The VAC describes the visual mismatch between the projected stereoscopic 3D image and the optical distance to the HMD screen. This conflict can be solved by using displays with correct focal distance. The light-field HMD of this study provides a close-to-continuous depth and high image resolution enabling a highly natural visualization. This paper presents the first user-study on the visual comfort of light-field displays with a close-to-market HMD based on complex interaction tasks. The results provide first evidence that the light-field technology brings clear benefits to the user in terms of physical use comfort, workload, and depth matching performance.     

Visual inspection with augmented reality head-mounted display: An Australian usability case study

Augmented reality (AR) is an Industry 4.0 technology. For more than a decade, advancements in AR technology and their applications have been expected to revolutionise the manufacturing industry and deliver quality and productivity gains. However, due to factors such as equipment costs, skills shortages and technological limitations of AR devices, operational deployment beyond prototypes has been constrained. Real-world, usability studies can explore barriers to implementation and improve system design. This paper details a mixed method usability case study of an AR head-mounted display (HMD) to perform a short, simple visual inspection task. Twenty-two participants from South Australian manufacturing businesses inspected a pump and pipe skid while working at height. Overall, workload demands for the task were considered acceptable and just below the “low” workload threshold (NASA Task Load Index, mean = 29.3) and the system usability was rated “average” (system usability scale, mean = 68.5). The results suggest the task did not place too high a burden on users and was an appropriate initial exposure to AR HMDs, but further refinement to the interface would be desirable before implementation to minimise frustration and promote learning. Users were enthusiastic and open-minded about the AR HMD although results indicate that even with recent advancements in AR HMD technology, interactions between the task, technology and environment continue to cause human and technical challenges—some of which are relatively straightforward to address but others are dependent on larger-scale efforts.     

Vection does not necessitate visually induced motion sickness

Vection, i.e. a visually induced illusory sense of self-motion, is assumed to play an essential role in visually induced motion sickness (VIMS). However, its precise role is unknown. Following the sensory conflict theory, a constant state of vection is not expected to lead to a visual-vestibular conflict whereas variability in vection, i.e. change in vection strength over time, would. In this study we investigated whether variability in vection rather than vection caused VIMS in participants exposed to constant optic flow using a head-mounted display. Strongest possible vection (i.e. 100% on a 0–100% scale) was reported by 16 out of 18 participants at some point during the experiment, with a total average vection score over the experiment of 58.6%. Initial motion sickness symptoms were reported by 15 out of 18 participants, although only averaging 1.78 on an 11-point scale. Neither average vection strength nor variability in vection were significantly correlated with motion sickness. Relating our findings to the literature, we argue that vection should be understood not as a direct cause of VIMS, but as a perceptual state still depending on other visual factors before VIMS occurs. Vection by itself, even if it is experienced strongly, does not necessitate VIMS.     

Natural perspective projections for head-mounted displays

The display units integrated in today's head-mounted displays (HMDs) provide only a limited field of view (FOV) to the virtual world. In order to present an undistorted view to the virtual environment (VE), the perspective projection used to render the VE has to be adjusted to the limitations caused by the HMD characteristics. In particular, the geometric field of view (GFOV), which defines the virtual aperture angle used for rendering of the 3D scene, is set up according to the display field of view (DFOV). A discrepancy between these two fields of view distorts the geometry of the VE in a way that either minifies or magnifies the imagery displayed to the user. It has been shown that this distortion has the potential to affect a user's perception of the virtual space, sense of presence, and performance on visual search tasks. In this paper, we analyze the user's perception of a VE displayed in a HMD, which is rendered with different GFOVs. We introduce a psychophysical calibration method to determine the HMD's actual field of view, which may vary from the nominal values specified by the manufacturer. Furthermore, we conducted two experiments to identify perspective projections for HMDs, which are identified as natural by subjects--even if these perspectives deviate from the perspectives that are inherently defined by the DFOV. In the first experiment, subjects had to adjust the GFOV for a rendered virtual laboratory such that their perception of the virtual replica matched the perception of the real laboratory, which they saw before the virtual one. In the second experiment, we displayed the same virtual laboratory, but restricted the viewing condition in the real world to simulate the limited viewing condition in a HMD environment. We found that subjects evaluate a GFOV as natural when it is larger than the actual DFOV of the HMD--in some cases up to 50 percent--even when subjects viewed the real space with a limited field of view.     

Lifting belts: a psychophysical analysis

The literature supporting the use of lifting belts has not demonstrated consistent trends. It was hypothesized that if lifting belts provide a biomechanical or motivational advantage then the participants in a psychophysical lift test should select a higher maximum acceptable weight of lift (MAWL). Eleven male and five female subjects participated in one session with a lifting belt and one session without a belt. The order of the belt sessions was counterbalanced. Each session was comprised of two psychophysical lifting tests varying only in the initial weight of the box. Repeated measures ANOVA showed no difference between the MAWL between belt sessions or between the two tests within a given session. Following the test, subjective evaluations of the belt were measured via a questionnaire. The psychophysical test results showed no change as a function of the belt condition. Thus, these results do not support the hypothesis that lifting belts increase trunk strength or motivate individuals to select a greater MAWL. Therefore, it must be concluded that belts do not offer a biomechanical or motivational advantage to the user.     

Brightness and contrast do not affect visually induced motion sickness in a passively-flown fixed-base flight simulator

BackgroundVisually Induced Motion Sickness (VIMS) or simulator sickness is often elicited by a visual stimulus that lacks the appropriate vestibular or proprioceptive feedback. In this study, we chose to investigate the effects of brightness and contrast of the visual scene on VIMS.HypothesisWe hypothesized that visual environments differing in brightness or contrast would differentially induce VIMS. The symptoms of VIMS should be most severe for the combination of high brightness and high contrast and conversely lowest for the low brightness and low contrast condition.Methods33 healthy subjects were tested in a fixed-base flight simulator. Each subject flew in four consecutive but counterbalanced conditions during one large experimental session. The four conditions consisted of identical recorded flight paths, differing only in brightness and contrast in a fully crossed design. VIMS was assessed with the Simulator Sickness Questionnaire and the Fast Motion Sickness scale administered during and after each condition. Postural Sway (PS) was measured after each condition.ResultsAll four brightness and contrast conditions were found to be effective in that they increased PS and elicited moderate VIMS. However, there were no main or interaction effects for brightness or contrast.ConclusionsOur findings suggest that brightness and contrast do not modulate the induction of VIMS. This conclusion may be limited to moderately provocative stimuli.     

Effect of passengers’ active head tilt and opening/closure of eyes on motion sickness in lateral acceleration environment of cars

This study examined the effect of passengers’ active head-tilt and eyes-open/eyes-closed conditions on the severity of motion sickness in the lateral acceleration environment of cars. In the centrifugal head-tilt condition, participants intentionally tilted their heads towards the centrifugal force, whereas in the centripetal head-tilt condition, the participants tilted their heads against the centrifugal acceleration. The eyes-open and eyes-closed cases were investigated for each head-tilt condition. In the experimental runs, the sickness rating in the centripetal head-tilt condition was significantly lower than that in the centrifugal head-tilt condition. Moreover, the sickness rating in the eyes-open condition was significantly lower than that in the eyes-closed condition. The results suggest that an active head-tilt motion against the centrifugal acceleration reduces the severity of motion sickness both in the eyes-open and eyes-closed conditions. They also demonstrate that the eyes-open condition significantly reduces the motion sickness even when the head-tilt strategy is used.

Practitioner Summary: Little is known about the effect of head-tilt strategies on motion sickness. This study investigated the effects of head-tilt direction and eyes-open/eyes-closed conditions on motion sickness during slalom automobile driving. Passengers’ active head tilt towards the centripetal direction and the eyes-open condition greatly reduce the severity of motion sickness.