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.     

"Conflicting" motion cues to the visual and vestibular self-motion systems around 0.06 Hz evoke simulator sickness

The basic question this research addressed was, how does simulator sickness vary with simulated motion frequency? Participants were 11 women and 19 men, 20 to 63 years of age. A visual self-motion frequency response curve was determined using a Chattecx posture platform with a VR4 head-mounted display (HMD) or a back-projected dome. That curve and one for vestibular self-motion specify a frequency range in which vestibular and visual motion stimuli could produce conflicting self-motion cues. Using a rotating chair and the HMD, a third experiment supported (p < .01) the hypothesis that conflicting cues at the frequency of maximum "crossover" between the curves (about 0.06 Hz) would be more likely to evoke simulator sickness than would conflicting cues at a higher frequency. Actual or potential applications of this work include a preliminary design guidance curve that indicates the frequency range of simulated motion that is likely to evoke simulator or virtual reality sickness; for simulators intended to operate in this frequency range, appropriate simulator sickness interventions should be considered during the design process.     

The effect of wearing a head-mounted display on the boundaries of the cervical range of motion based on perceived comfort in a static posture

Virtual Reality - The head-mounted display (HMD) for virtual reality (VR) systems is becoming more popular due to technological advancements, providing users with a more immersive experience. Since...     

CAVE and HMD: distance perception comparative study

Virtual Reality - This paper proposes to analyse user experience using two different immersive device categories: a cave automatic virtual environment (CAVE) and a head-mounted display (HMD). While...     

基于VAPS的虚拟航空仪表显示系统

虚拟航空仪表系统是飞行模拟器的重要组成部分.结合虚拟仿真技术和飞行模拟器样机的技术要求,阐述了虚拟航空仪表的构建和虚拟仪表系统的实现方法.系统采用软件VAPS进行虚拟仪表的外形设计;采用VAPS和C++混合方式进行驱动显示;采用C编程语言实现虚拟航空仪表系统内部的通讯,网络通讯采用UDP/IP通讯形式.仿真结果证明,V...     

Use of physiological signals to predict cybersickness

Cybersickness is a common and unpleasant side effect of virtual reality immersion. We measured physiological changes that were experienced by seated subjects who interacted with a virtual environment (VE) first while viewing a display monitor and second while using a head-mounted display (HMD). Comparing results for these two conditions let us identify physiological consequences of HMD use. In both viewing conditions, subjects rated the severity of their symptoms verbally and completed a post-immersion cybersickness assessment questionnaire. In the HMD viewing condition but not in the display monitor condition, verbal reports of cybersickness severity increased significantly relative to baseline. Half of the subjects chose to exit the VE after six minutes of HMD use and reported feeling some nausea at that time. We found that changes in stomach activity, blinking, and breathing can be used to estimate post-immersion symptom scores, with R² values reaching as high as 0.75. These results suggest that HMD use by seated subjects is strongly correlated with the development of cybersickness. Finally, a linear discriminant analysis shows that physiological measures alone can be used to classify subject data as belonging to the HMD or monitor viewing condition with an accuracy of 78%.     

基于全景成像的增强现实系统

建立完整的基于全景成像的增强现实系统,将全景图像采集系统放置在场景中采集真实图像,佩戴头盔显示器和头部跟踪器的观察者可以在其他地方观看在真实图像中添加了虚拟信息的增强图像,解决图像采集装置与头盔显示器分离时增强现实系统的技术难点。实验结果表明,全景成像方法对于亮度差异较大的图像有较好的拼接效果,适用于室外复杂环境的图像拼接,全景图像的局部增强显示效果良好。     

飞行模拟系统人机交互设计

针对增强飞行模拟训练的沉浸感,提高飞行模拟训练的效率和效果的目的,以真实飞行训练为基础,利用UI分类和设计方法,对飞行训练关键交互操作以及核心人机交互UI进行研究并加以整合,运用虚拟仿真技术,着力解决飞行模拟训练中人机交互体验沉浸感低,人性化设计不足,交互方式单一,训练效率和效果不佳等问题。提出将飞行模拟训练系统人机交互UI分为沙盒人机交互UI模块,平显、仪表人机交互UI模块,头戴式显示器人机交互UI模块,样机驾驶舱人机交互环境模块四个部分,完成了四个模块的设计,并基于Unigine引擎实现了四个模块。有效提升了飞行模拟训练的效率和训练效果。     

A virtual reality keyboard with realistic haptic feedback in a fully immersive virtual environment

This study presents a 3D virtual reality (VR) keyboard system with realistic haptic feedback. The system uses two five-fingered data gloves to track finger positions and postures, uses micro-speakers to create simulated vibrations, and uses a head-mounted display (HMD) for 3D display. When users press a virtual key in the VR environment, the system can provide realistic simulated key click haptic feedback to users. The results of this study show that the advantages of the haptic VR keyboard are that users can use it when wearing HMDs (users do not need to remove HMDs to use the VR keyboard), the haptic VR keyboard can pop-up display at any location in the VR environments (users do not need to go to a specific location to use an actual physical keyboard), and the haptic VR keyboard can be used to provide realistic key click haptic feedback (which other studies have shown enhances user performance). The results also show that the haptic VR keyboard system can be used to create complex vibrations that simulate measured vibrations from a real keyboard and enhance keyboard interaction in a fully immersive VR environment.     

Binocular vision in a bi-ocular world: new-generation head-mounted displays avoid causing visual deficit

Our previous research highlighted adverse visual effects after wearing a binocular head-mounted display (HMD) for a 10 min stereoscopic visualization task. We have since proposed a theoretical, explanation based on the conflict between the depth. Such cues presented by image disparity and image focal depth. Such conflict, however, is not evident in all HMD configurations, and we replicated our early trials using a new-generation bi-ocular HMD produced by Virtuality Entertainment Ltd. Using similar, conventional optometric procedures with 50 participants, we observed no problems in the use of this display for immersion periods of to 30 min. This study demonstrates that effective HMDs can be produced through careful design and precision engineering. It also suggests a difference between the presentation of binocular and bi-ocular images and the requirements that they place on the visual system. Factors to consider in the future development of binocular displays are discussed.     

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.     

A psychophysical and questionnaire investigation on the spatial disorientation triggered by cockpit layout and design

This study assessed Taiwanese air force combat jet pilots' ability to cope with spatial disorientation (SD) triggered by cockpit layout and design. The measurement items of psychophysical questionnaire were ranked by 325 air force combat jet pilots. This study prioritized the causes of SD perceived by combat jet pilots resulted from the unfamiliarity with instruments on aircraft undergoing flight training, the aircraft's cockpit canopy and the layout of instruments in the cockpit. A significant difference was found between with-SD experience and without-SD experience subjects' responses from adapting to the size of instruments in the cockpit, and from the helmet-mounted display (HMD). Considerable association was discernible between the position of instruments in the cockpit and combat jet models accrued; as well as between the helmet-mounted display (HMD) and combat jet models accrued. The study identify main cockpit layout and design causing SD of Taiwanese pilots based on combat jet models to eliminate the risk of SD, intensify SD training on preventing SD and provide pilots with skills to anticipate and assess the risk of SD during mission planning, and provide references to the military for future procurement of new aircraft models.Relevance to industryThese results provide important information to the defense manufacturers for designing the cockpit layout of combat jets to prevent SD of specific pilots. Finally, the results show the contribution of ergonomics to support military operational commanders in the design of training and prevention of SD.     

Impact of aviation highway-in-the-sky displays on pilot situation awareness

Thirty-six pilots (31 men, 5 women) were tested in a flight simulator on their ability to intercept a pathway depicted on a highway-in-the-sky (HITS) display. While intercepting and flying the pathway, pilots were required to watch for traffic outside the cockpit. Additionally, pilots were tested on their awareness of speed, altitude, and heading during the flight. Results indicated that the presence of a flight guidance cue significantly improved flight path awareness while intercepting the pathway, but significant practice effects suggest that a guidance cue might be unnecessary if pilots are given proper training. The amount of time spent looking outside the cockpit while using the HITS display was significantly less than when using conventional aircraft instruments. Additionally, awareness of flight information present on the HITS display was poor. Actual or potential applications of this research include guidance for the development of perspective flight display standards and as a basis for flight training requirements.     

Binocular configurations of a night-flight head-mounted display

Visual configurations for a head-mounted display (HMD) are evaluated with binocular asymmetry as the defining characteristic. With such a configuration the optimum compromise between binocular rivalry, weight and usefulness of see-through at night is sought. A dichoptic area of interest and the addition of a window-frame are shown to be simple and useful aspects of a binocular asymmetric HMD configuration. The dichoptic area of interest combines a large, low-resolution image in one eye with a small, high-resolution image in the other. A window-frame acts as a strong fusion lock and improves the visual quality of the binocular image for some configurations.     

Development and evaluation of BCI for operating VR flight simulator based on desktop VR equipment

Advancement of brain-computer interface (BCI) has shown its applications in various scenarios, including flight control. Flight simulator is a crucial part for aircraft design or experiment. Desktop virtual reality (VR)-based flight is a perfect choice for overcoming existing problems in head-mounted VR flight simulations, such as dizziness and isolation, which make interaction and sharing very difficult. In this paper, a BCI based on the steady-state visual evoked potential paradigm and a VR flight simulator were developed and integrated. The performance of the developed system was evaluated quantitatively for comparative studies. Experimental results show that the developed system is very convenient and suitable for VR flight simulations. The average operating accuracies with plane and VR visual stimuli are 81.6% and 86.8%, respectively. The VR visual stimuli can improve the average operating accuracy by 5.2% compared with the plane visual stimuli.     

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.     

基于VAPS虚拟仪表反走样设计仿真实现

针对飞机模拟机虚拟仪表设计仿真时存在刻度线走样、刻度线位置不准确以及会产生锯齿现象等缺陷而进行反走样技术研究,提出区域采样技术和Bresenham反走样算法结合,重点在刻度线、字符的反走样技术上对其进行优化设计与研究,提高虚拟仪表画面的显示质量。通过VAPS软件完成了虚拟仪表设计与仿真。试验表明,该算法能够在虚拟仪表研发中实现反走样设计,达到飞机机载电子显示系统对其性能的高要求和标准。     

教学飞行仿真模拟器的开发与应用

飞行模拟器在Windows环境下，用Vc＋＋和Open GL、Open GVS等软件开发工具，采用面向对象的程序设计方法实现仪表仿真、视景仿真、飞行方程仿真和控制台仿真的系统仿真功能。多功能飞行模拟器采用具有真实驾驶杆、油门杆、脚蹬和各种按钮开关的驾驶舱，以一台工控机为主控机外挂几台微机组成，通过网络协议完成实时信息传递，数据交换和条件设置。此设备既具有良好的人机交互功能，又可作为本科生演示和相关专业研究生的实验设备，也可以利用此平台进行仪表、视景等系统的继续开发工作，因此具有良好的可扩展性。     

Real world teleconferencing

We've been exploring how augmented reality (AR) technology can create fundamentally new forms of remote collaboration for mobile devices. AR involves the overlay of virtual graphics and audio on reality. Typically, the user views the world through a handheld or head-mounted display (HMD) that's either see-through or overlays graphics on video of the surrounding environment. Unlike other computer interfaces that draw users away from the real world and onto the screen, AR interfaces enhance the real world experience. For example, with this technology doctors could see virtual ultrasound information superimposed on a patient's body.