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In see-through helmet-mounted displays (HMDs), image-intensifier tubes are located on the sides of the helmet. This HMD design increases the effective interpupillary distance and exposes the observer to hyperstereopsis. The modification of three-dimensional space perception by hyperstereopsis in laboratory studies is well known. Little is known, however, about its effects in real, operational conditions. The present study investigated the effects of hyperstereopsis on visual perception in helicopter pilots during the first flight of a night-flight training program using a see-through HMD. Fifteen pilots’ percepts of distance and height under hyperstereoscopic viewing were assessed using a double-distance estimation task in standard flight circuits. In addition, two questionnaires were used to characterize the perceptual effects induced by hyperstereoscopic viewing during the first night flight, and to determine whether any aftereffects were still present during the 24-h period following the flight. Height and distance estimation errors were observed. On average, pilots tended to underestimate the near plane relative to the farther plane in the double-distance estimation task; this is the inverse of what is commonly observed under natural viewing. We ascribed this effect to a non-linear decrease in the hyperstereopsis effect with viewing distance. Six pilots experienced sensory illusions resembling a distortion of apparent visual space: the impression of “sinking into a hole” when landing, of objects appearing closer than they actually were, and reduced in size. Four pilots cited landing as the most difficult situation encountered during the flight. Only minor complaints were reported for the 24-h period following the flight. The results of this field study represent a step towards characterizing the perceptual and operational impact of this display technology in helicopter pilots during initial exposure. [ABSTRACT FROM AUTHOR]

The paper presents selected results of analytical and construction works executed at the Air Force Institute of Technology (AFIT) in the context of possibilities of supporting the actions of a helicopter crew, i.e., pilot-crew commander, pilot-operator of on-board systems, and on-board technician participating in aviation/maritime search and rescue missions. Such support is based on using the helmet-mounted display systems SWPL1 "Cyklop" and NSC1 "Orion" for information from the observation-targeting heads and verbal communication with the survivor. Selected imaging and verbal communication devices installed on aircraft operated by the Polish Armed Forces, which are used in aviation/maritime search and rescue actions, are discussed. Particular attention is drawn to the problems associated with the integrated avionics systems of helmet-mounted imaging of piloting-navigation parameters and the helmet-mounted imaging of information from the observation-targeting heads, i.e., the on-board radio direction finder system and emergency radio, which are part of the integrated communication system. Sample structural solutions for such systems and the possibilities of their application in search and rescue missions are presented. [ABSTRACT FROM AUTHOR]

Our laboratory has developed a skill learning support environment “Motion Navigator”, by which a learner can train himself/herself for a motion just by following model motion displayed on his/her HMD with AR. we have developed a golf learning support environment by improving “Motion Navigator”, which takes the necessary elements into account for a learner to mimic and to practice golf swing. By displaying learner's operation superimposed with the model motion simultaneously, the system can give the learner awareness of mistake of his/her motion. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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Abstract: Head-mounted displays (HMDs) allow users to immerse in a virtual environment (VE) in which the user’s viewpoint can be changed according to the tracked movements in real space. Because the size of the virtual world often differs from the size of the tracked lab space, a straightforward implementation of omni-directional and unlimited walking is not generally possible. In this article we review and discuss a set of techniques that use known perceptual limitations and illusions to support seemingly natural walking through a large virtual environment in a confined lab space. The concept behind these techniques is called redirected walking. With redirected walking, users are guided unnoticeably on a physical path that differs from the path the user perceives in the virtual world by manipulating the transformations from real to virtual movements. For example, virtually rotating the view in the HMD to one side with every step causes the user to unknowingly compensate by walking a circular arc in the opposite direction, while having the illusion of walking on a straight trajectory. We describe a number of perceptual illusions that exploit perceptual limitations of motion detectors to manipulate the user’s perception of the speed and direction of his motion. We describe how gains of locomotor speed, rotation, and curvature can gradually alter the physical trajectory without the users observing any discrepancy, and discuss studies that investigated perceptual thresholds for these manipulations. We discuss the potential of self-motion illusions to shift or widen the applicable ranges for gain manipulations and to compensate for over- or underestimations of speed or travel distance in VEs. Finally, we identify a number of key issues for future research on this topic. [Copyright &y& Elsevier]

Abstract: Motion sickness (MS) can be a debilitating side-effect not just of sea travel, but also when immersed in video games or virtual environments (visually induced MS). To explore the impact of visual display parameters on motion sickness, we presented footage taken on an automobile race track to different groups of observers during three experiments. In Experiment 1, one group watched the movie wearing a head-mounted display (HMD) and a second group looked at a large projection screen with unrestricted view. Resolution and visual angle were equated. In contrast to common assumption, the projection screen produced significantly higher motion sickness scores than the HMD. To understand this rather surprising result, two further groups watched the movie with a limited field of view and reduced display angle, either through a synoptic device or a reduction screen (Experiment 2). Visually induced MS was reduced in both groups to the same extent. In Experiment 3, a fifth group of observers looked at the large screen with a limited field of view, but with unrestricted display angle. Results again showed decreased sickness scores. We conclude that another factor above and beyond display angle is critical to explain visually induced MS, namely the visual surround of the display. If present, the surround increases visually induced MS by causing an additional intra-visual conflict that makes it harder for the visual system to dominate the vestibular information and thus increases the nauseogenic conflict between visual and vestibular information. [Copyright &y& Elsevier]

Abstract: The experience of simulator sickness (SS) during head-mounted display (HMD) exposure continues to be a problem. The aim of these two experiments was to examine the effect of delay on SS while viewing a real, live video scene via an HMD. An object search task was performed in both experiments. Experiment 1 examined 0 and 200ms of delay and Experiment 2 examined 0, 145, and 300ms of delay. SS did not differ as a function of delay. However, SS increased as duration exposure increased in both experiments. In Experiment 1, SS was greater during the first experimental session than the second. SS did not differ between those who donned an HMD and a No HMD control condition in Experiment 2. It is possible that this is due to adaptation to repeated exposure to the sickening stimulus. This adaptation could have confounded the delay effects from Experiment 1. For this reason, a second experiment with an increased intersession interval was conducted. Intersession intervals for Experiment 2 were increased to 11–14days from 7days in Experiment 1. However, no effect of delay or session was found in Experiment 2. These results suggested that SS does not increase as a function of delay, but exposure duration increases SS. Also, performing repetitive head movements alone may have elicited symptoms of SS. As reported by other researchers, it appears that adaptation can occur to motion sickness stimuli with intersession intervals of up to 7days, but not with 11–14days. Other characteristics of HMD VEs need to be examined because SS occurs and delay does not appear to be as strong of a causal factor as once thought. [Copyright &y& Elsevier]

Objective: We examined the effects of several display characteristics of head-mounted displays (HMDs) on simulator sickness (SS).Background: Technological limitations, such as display delay and reduced field of view (FOV), affect perception when using an HMD and are often thought to be related to SS. Few studies have examined the relationship between FOV and geometric FOV (image scale factor) or how HMD characteristics may interact.Method: Participants made active head movements to locate objects when viewing a live video via an HMD.Results: Compared with no added delay, an additional 200 ms of display delay did not result in increased SS, as measured by the Simulator Sickness Questionnaire. Furthermore, an effect of image scale factor on SS was not revealed. However, SS was greater when peripheral vision was occluded than when it was not. Peripheral vision moderated the effects of image scale factor and delay on head movement velocity.Conclusion: Occluding peripheral vision may subject HMD users to the potential detrimental consequences of HMD characteristics more than when peripheral vision of the external environment is available, resulting in more SS. Future research should investigate to what extent peripheral vision can be occluded without increasing SS and without sacrificing realism and presence.Application: To reduce the occurrence of SS, a degree of peripheral vision of the external world should be provided. Furthermore, users and designers should be aware that head movement behavior may be affected by HMD characteristics. [ABSTRACT FROM AUTHOR]

Abstract: Introduction: Lag between head movement and the time to render the visual consequences of the movement during head mounted display (HMD) applications presents challenges in the appearance of a stable image. This appearance of an image to “lag” behind or “swim” about may cause detriments in user performance, lack of user acceptance, and simulator sickness. These known potential consequences of HMD use motivated the current work to explore the human capability to detect display lag. The aim in this study was to gain a better understanding of the threshold for display lag detection and what variables affect this threshold. Methods: Twenty four subjects completed a repeated-measures three field of view (FOV; 10°, 38°, and full monocular) X two psychophysical technique (forced-choice and simple) experimental design. Passive sinusoidal head movements about the yaw axis were generated by an oscillating chair. A visual scene consisting of vertical bars was projected by an optokinetic drum moving in a sinusoidal fashion with the subjects. Subjects reported whether the scene lagged behind head movement. Results: The grand threshold mean for lag detection was 147.64ms (SD =84.91). The median was 130ms and the 25th and 75th percentiles were 84.17ms and 206.25ms, respectively. Lag thresholds were not systematically influenced by either FOV or psychophysical technique. Discussion: Naïve subjects in the current study were less sensitive to lag as compared to thresholds reported in previous HMD studies, which provided lag detection strategies and practice [e.g., 77ms; Ellis, Mania, Adelstein, & Hill, 2004]. Future examinations using the current paradigm should provide detection strategies and more practice. [ABSTRACT FROM AUTHOR]

Objective: The aim of this study was to replicate the finding that multisensory integration with a head-mounted display (HMD) is particularly difficult when a person is walking and hearing sound from a free-field speaker, and to extend the finding with a response method intended to reduce workload. Background: HMDs can support the information needs of workers whose work requires mobility, but some low-cost solutions for delivering auditory information may be less effective than others. Method: For the study, 24 participants detected whether shapes moving on the HMD screen made a sound appropriate to their forms when they collided with other shapes. Independent variables were self-motion (participants were mobile or seated), sound delivery (free-field speakers or an earpiece), and response method (noting mismatches via a mental count or via a manual clicker). Results: Unexpectedly, overall mismatch task accuracy was worse with the clicker (p = .027) than without. Participants also reported that it was harder to time-share the mismatch task with clicker responses (p = .033). In the clicker condition, self-motion and sound delivery interacted but in the opposite direction to the previous study. Conclusion: The best way of delivering auditory information to mobile workers performing a multisensory integration task with an HMD may depend on whether responding involves mental load or manual load. Broader theories are needed to capture factors influencing performance. Application: Until more powerful theory is developed, designers should perform careful formative and summative tests of whether the activities to be performed by mobile HMD wearers will make some sound delivery solutions less effective than others. [ABSTRACT FROM AUTHOR]

Objective: The aim of this study was to assess how background visual motion and the relative movement of sound affect a head-mounted display (HMD) wearer's performance at a task requiring integration of auditory and visual information. Background: HMD users are often mobile. A commercially available speaker in a fixed location delivers auditory information affordably to the HMD user. However, previous research has shown that mobile HMD users perform poorly at tasks that require integration of visual and auditory information when sound comes from a free-field speaker. The specific cause of the poor task performance is unknown. Method: Participants counted audiovisual events that required integration of sounds delivered via a free-field speaker and vision on an HMD. Participants completed the task while either walking around a room, sitting in the room, or sitting inside a mobile room that allowed separate manipulation of background visual motion and speaker motion. Results: Participants' accuracy at counting target audiovisual events was worse when participants were walking than when sitting at a desk, p = .032. Compared with when they were sitting at a desk, participants' accuracy at counting target audiovisual events showed a trend to be worse when they experienced a combination of background visual motion and the relative movement of sound, p = .058. Conclusion: Multisensory integration performance is least effective when HMD users experience a combination of background visual motion and relative movement of sound. Eye reflexes may play an important role. Application: Results apply to situations in which HMD wearers are mobile when receiving multimodal information, as in health care and military contexts. [ABSTRACT FROM AUTHOR]

Background: Unilateral spatial neglect (USN) is most damaging to an older stroke patient who also has a lower performance in their activities of daily living or those elderly who are still working. The purpose of this study was to understand more accurately pathology of USN using a new HMD system. Methods: Two stroke patients (Subject A and B) participated in this study after gaining their informed consent and they all had Left USN as determined by clinical tests. Assessments of USN were performed by using the common clinical test (the line cancellation test) and six special tests by using HMD system in the object-centered coordinates (OC) condition and the egocentric coordinates (EC) condition. OC condition focused the test sheet only by a CCD. EC condition was that CCD can always follow the subject's movement. Moreover, the study focused on the effect of the reduced image condition of real image and the arrows. Results: In Patient A who performed the common test and special tests of OC and EC conditions, the results showed that for the line cancellation test under the common condition, both of the percentage of the correct answers at the right and left sides in the test sheet was 100 percent. However, in the OC condition, the percentage of the correct answers at the left side in the test sheet was 44 percent and the right side was 94 percent. In the EC condition, the left side was 61 percent and the right side was 67 percent. In Patient B, according to the result of the use of reduced image condition and the arrows condition by HMD system, these line cancellation scores more increased than the score of the common test. Conclusions: The results showed that the assessment of USN using an HMD system may clarify the left neglect area which cannot be easily observed in the clinical evaluation for USN. HMD may be able to produce an artificially versatile environment as compared to the common clinical evaluation and treatment. [ABSTRACT FROM AUTHOR]

Objective: We provide a review and analysis of much of the published literature on visual perception issues that impact the design and use of head-mounted displays (HMDs).Background: Unlike the previous literature on HMDs, this review draws heavily from the basic vision literature in order to help provide insight for future design solutions for HMDs.Method: Included in this review are articles and books found cited in other works as well as articles and books obtained from an Internet search.Results: Issues discussed include the effect of brightness and contrast on depth of field, dark focus, dark vergence, and perceptual constancy; the effect of accommodation-vergence synergy on perceptual constancy, eyestrain, and discomfort; the relationship of field of view to the functioning of different visual pathways and the types of visual-motor tasks mediated by them; the relationship of binocular input to visual suppression; and the importance of head movements, head tracking, and display update lag.Conclusion: This paper offers a set of recommendations for the design and use of HMDs.Application: Consideration of the basic vision literature will provide insight for future design solutions for HMDs. [ABSTRACT FROM AUTHOR]

Ever since the development of the first applications in image-guided therapy (IGT), the use of head-mounted displays (HMDs) was considered an important extension of existing IGT technologies. Several approaches to utilizing HMDs and modified medical devices for augmented reality (AR) visualization were implemented. These approaches include video-see through systems, semitransparent mirrors, modified endoscopes, and modified operating microscopes. Common to all these devices is the fact that a precise calibration between the display and three-dimensional co-ordinates in the patient's frame of reference is compulsory. In optical see-through devices based on complex optical systems such as operating microscopes or operating binoculars—as in the case of the system presented in this paper—this procedure can become increasingly difficult since precise camera calibration for every focus and zoom position is required. We present a method for fully automatic calibration of the operating binocular Varioscope™ MS AR for the full range of zoom and focus settings available. Our method uses a special calibration pattern, a linear guide driven by a stepping motor, and special calibration software. The overlay error in the calibration plane was found to be 0.14-0.91 mm, which is less than 1% of the field of view. Using the motorized calibration rig as presented in the paper, we were also able to assess the dynamic latency when viewing augmentation graphics on a mobile target; spatial displacement due to latency was found to be in the range of 1.1-2.8 mm maximum, the disparity between the true object and its computed overlay represented latency of 0.1 s. We conclude that the automatic calibration method presented in this paper is sufficient in terms of accuracy and time requirements for standard uses of optical see-through systems in a clinical environment. [ABSTRACT FROM AUTHOR]

We conducted 2 experiments to investigate the clutter-scan trade-off between the cost of increasing clutter by overlaying complex information onto the forward field of view using a helmet-mounted display (HMD) and the cost of scanning when presenting this information on a handheld display. In the first experiment, this trade-off was examined in terms of the spatial accuracy of target cuing data in a relatively sparse display; in the second, the spatial accuracy of the cue was varied more radically in an information-rich display. Participants were asked to detect and identify targets hidden in the far domain while performing a monitoring task in the near domain using either an HMD or a handheld display. The results revealed that on a sparse display, the reduced scanning from the HMD presentation of cuing out-weighed the costs of clutter for cued targets, regardless of cue precision, but no benefit was found for uncued targets. When the HMD displayed task-irrelevant information, however, target detection was hindered by the extraneous clutter in the forward field of view relative to the handheld display condition, and this cost of clutter increased as the amount of data that needed to be inspected increased. Potential applications of this research include the development of design considerations for head-up displays for aviation and military applications. [ABSTRACT FROM AUTHOR]

Presents a study which looked at the design and merits of subtractive-color active-matrix liquid-crystal display (AMLCD) used for helmet-mounted displays. Details on the usage of subtractive-color active-matrix liquid-crystal display; Discussion on the image quality of a subtractive-color AMLCD; Findings of the study.