Comparison of visual fatigue caused by head-mounted display for virtual reality and two-dimensional display using objective and subjective evaluation

This study aimed to evaluate objective and subjective visual fatigue experienced before and after performing a visual task while using a head-mounted display for virtual reality (VR-HMD) and two-dimensional (2D) display. Binocular fusion maintenance (BFM) was measured using a binocular open-view Shack–Hartmann wavefront aberrometer equipped with liquid crystal shutters. Twelve healthy subjects performed the BFM test and completed a questionnaire regarding subjective symptoms before and after performing a visual task that induces low visually induced motion sickness (VIMS). BFM (p = .87) and total subjective eye symptom scores (p = .38) were not significantly different between both groups, although these values were significantly lower after the visual task than before the task within both groups (p < .05). These findings suggest that visual fatigue after using a VR-HMD is not significantly different from that after using a 2D display in the presence of low-VIMS VR content.

Practitioner summary: Objective and subjective evaluation of visual fatigue were not significantly different with the use of a head-mounted display for virtual reality (VR-HMD) and two-dimensional display. These results should be valuable not only to engineers developing VR content but also to researchers involved in the evaluation of visual fatigue using VR-HMD.

Abbreviations: VR: virtual reality; VR-HMD: head-mounted display for virtual reality; BFM: binocular fusion maintenance; BWFA: binocular open-view Shack–Hartmann wavefront aberrometer     

立体图像重定技术研究综述

随着立体图像显示技术的不断发展和广泛应用,为了保证图像在不同显示条件下的观赏质量,立体图像重定技术在工业界和学术界备受关注.由于立体图像的特殊性,传统二维图像重定技术难以直接应用于三维立体图像.文中在分析了立体视觉的特点及其对人的心理影响的基础上,阐述了立体图像重定技术所要解决的问题;然后将该技术领域内的已有研究文献按照方法类型分类,并分别对各类方法进行了综述和分析;最后对现有立体图像重定技术进行了总结,分析了其中存在的问题,提出了问题的解决方法和未来的研究思路.     

立体视频会议中基于对象的中间视生成

描述了立体视频会议系统中实现视点适应的算法,其目的是获得真实的远程三维感觉,这需要通过从基线距离较大的立体摄像点中获得中间视。提出的方法首先识别前景和背景区域,并对前景对象进行视差估计。在视差估计中使用了分级的基于块的立体匹配方法,同时考虑了邻域的平滑性约束。然后利用视差一致性准则进行遮挡区域的检测,并对遮挡区域的视差进行补偿。最后在假设头肩像模型的条件下,提出了一种基于对象的中间视插值算法。实验结果表明,文中提出的方法可以获得高质量的中间视。     

基于双视点重构的3维自由立体显示前景视觉的优化

基于双视点重构的立体显示原理建立虚拟3维空间到真实空间的映射关系,据此诠释前景畸变产生的原因是虚拟空间到真实空间映射关系的非线性,进而提出以改变视点设置与变形虚拟3维空间相结合的方法改变水平位差分布,实现前景立体视觉的优化,并且评估了该方法校正前景畸变的效果以及对前景和远景双影的影响,最后,提出基于动态视点更新和动态空间压缩的立体全景视觉优化策略。与美国DTI公司的3维立体显示软件TextureEyes相比,笔者据此开发的3维立体显示软件的前景畸变和双影减小明显。     

基于视差和阈值分割的立体视频对象提取

视频对象分割和提取是编码、通信以及视频检索等基于内容视频处理中的关键问题,为了从只有单一全局运动、含有重叠多对象的立体视频序列中提取对象,提出了一种基于视差分析和阈值分割的对象提取方法。该方法首先用改进的区域匹配法进行立体视差估计,并通过合理减少匹配窗的运算量及根据视差特性设定搜索路径来加快匹配速度;然后针对图像中不同的对象分别采用迭代阈值法和自适应阈值法进行二次分割;最后从阈值分割结果中提取出各个对象。实验提取出的各深度层视频对象效果良好,表明该方法是一种有效的适用于全局运动的立体视频序列对象提取方法。     

模拟注视眼动的多聚焦彩色图像融合

多聚焦图像存在聚焦和离焦区。通常聚焦区吸引人的注意力,具有突出的视觉显著性。提出一种模拟人类视觉机制的彩色图像融合方法。利用超复数傅里叶变换改进传统显著性检测算法,直接检测彩色图像显著度;模拟人类视觉的注视眼动机制对图像尺度稍微扰动,并对不同尺度下获得的图像显著度进行累加;选择累计显著度最大的源图像像素构建融合图像,并采用颜色相似性准则处理边界带像素。相关仿真实验表明,超复数傅里叶变换充分利用了源图像的颜色信息,累加显著度能提高峰值信噪比并减少均方根误差。实验结果表明该方法可得到超过36 dB的峰值信噪比和小于个位数的均方误差,在图像融合中可得到相对好的主观视觉效果。     

时空联合视差优化的立体视频重定向

目的智能适配显示的图像/视频重定向技术近年受到广泛关注。与图像重定向以及2D视频重定向相比,3D视频重定向需要同时考虑视差保持和时域保持。现有的3D视频重定向方法虽然考虑了视差保持却忽略了对视差舒适度的调整,针对因视差过大和视差突变造成视觉不舒适度这一问题,提出了一种基于时空联合视差优化的立体视频重定向方法,将视频视差范围控制在舒适区间。方法在原始视频上建立均匀网格,并提取显著信息和视差,进而得到每个网格的平均显著值;根据相似性变化原理构建形状保持能量项,利用目标轨迹以及原始视频的视差变化构建时域保持能量项,并结合人眼辐辏调节原理构建视差舒适度调整能量项;结合各个网格的显著性,联合求解所有能量项得到优化后的网格顶点坐标,将其用于确定网格形变,从而生成指定宽高比的视频。结果实验结果表明,与基于细缝裁剪的立体视频重定向方法对比,本文方法在形状保持、时域保持及视差舒适度方面均具有更好的性能。另外,使用现有的客观质量评价方法对重定向结果进行评价,本文方法客观质量评价指标性能优于均匀缩放和细缝裁剪的视频重定向方法,时间复杂度较低,每帧的时间复杂度至少比细缝裁剪方法降低了98%。结论提出的时空联合...     

Distance estimation of near‐field visual objects in stereoscopic displays

Stereoscopic displays have a promising future because of recent advancements and popularity of handheld devices and maturing head mounted displays. Gesture interaction such as pointing, selection, pinching, and manipulation are now possible in the current virtual environments, where accurate distance judgment is required. In this paper, we address the perception of exocentric distance in stereoscopic displays under two target orientations: horizontal and vertical. Three parallax conditions (on screen, 5 cm from screen, and 10 cm from screen) were considered, where the screen was fixed at a distance of 100 cm from the observer. Four levels of center‐to‐center distance between 10 and 50 cm were employed. The perceptual matching task revealed underestimation in all conditions. The overall judgment of exocentric distance was only about 80% of the actual. We also found a main effect of distance and interaction between layout and distance to be significant. The two important findings of this study are that underestimation of exocentric distance increases as the separation between virtual targets increases and that in vertical orientation, accuracy increases with closer targets. However, the main effects of layout and parallax on accuracy of judgment were not significant. Engineering implications of the results are also discussed in this paper.     

眼动仪与视线跟踪技术综述

文章在回顾视线跟踪技术的研究历程基础上,定义了视线跟踪的基本概念和参数。分析了六种主要视线跟踪技术原理,比较了每种技术的优、缺点。介绍了眼动仪硬件设备的研制和发展状况,对比了几种主要的眼动仪性能。最后,探讨了视线跟踪数据的处理软件和方法,并对视线跟踪技术的应用前景进行总结和展望。     

立体视频传输中右通道整帧丢失的错误掩盖算法

当立体视频流通过网络传输时,由于网络拥塞等造成的数据包丢失常常会引起整个视频帧丢失.鉴于此,本文基于H.264/AVC视频编码标准提出了两种立体视频整帧错误掩盖方案,它们分别利用立体视频序列的不同特点来进行恢复.结果显示,利用这两种算法恢复的图像均能获得很好的主客观质量.     

快速视差范围估计算法及其应用

视差范围估计在立体匹配中非常重要,准确的视差范围能提高立体匹配的精度和速度.为此提出一种基于匹配代价搜索和图像细分的快速视差范围估计算法.该算法将输入图像均匀分成多个图像块,采用匹配代价搜索计算每一图像块的视差,找到视差最大(最小)的图像块,并利用迭代细分规则将该图像块继续分成更小的子块,直至得到稳定的最大(最小)视差;利用匹配代价图对图像块进行可靠性检测,以解决弱纹理块容易误匹配的问题.实验结果表明,文中算法在保持97.3%的平均命中率的同时将立体匹配的平均搜索空间降低了27.7%,比采用传统算法可以得到更准确的视差范围;将该算法应用于立体匹配算法中降低了其平均误匹配率,并将计算时间缩短了20%~45%.     

基于眼动记录与分析技术的测谎研究

为进一步提高测谎的准确度,加快促成测谎结论成为刑事诉讼中的证据,提出一种低成本的将眼睛变化线索用于测谎的方案。首先设计了一种低成本的眼动记录系统记录眼动信号,提出分段加权Hough变换算法跟踪虹膜,利用梯度积分投影函数检测眨眼,采用差分图像估计眼睛张开程度。然后建立了眼动轨迹、眨眼频率及眼睛张开程度等眼动特征与说谎的关系模型。实验取得的眼动特征检测精度证明采用低成本眼动记录系统基本可以满足测谎需求,测谎实验结果证明了本文方法用于测谎或辅助测谎的可行性。     

一种基于块匹配的立体视频错误隐藏方法*

提出了一种基于块匹配的立体视频错误隐藏方法,充分利用了空间相关性及左右视点间的视差信息的相关性.实验结果表明所提方法有较好的错误隐藏性能.     

Evaluation of stereoscopic picture quality with CFF

The method of binocular stereoscopic imaging has attracted attention as a simple and technically feasible means of three-dimensional (3-D) display. It has been said, however, that the binocular picture system is more fatiguing to view than a conventional two-dimensional picture, such as the current television picture. The main objective of this paper is to evaluate quantitatively fatigue caused by binocular stereoscopic picture viewing, to clarify the basic characteristics of this type of picture. Various measurement methods of fatigue have been proposed, and that using the critical flicker frequency (CFF) has found wide use in measurement of mental fatigue and is easy to make. Actual measurement in this study used the CFF value obtained in a descending series of the method of limits, normalized to the value at the start of measurement for each observer, and the CFFs of all observers then averaged. It was found that the measurements produced stable and highly accurate results. CFFs of the observers of a current television picture and a binocular stereoscopic television picture were measured. It was found that the conventional television did not cause a statistically significant decrease in CFF—even over 1?h of viewing—but that the stereoscopic television did cause a significant CFF decrease within 30?min. It was also found that the CFF decreases are related to a subjective feeling of fatigue. From these results, it was concluded that CFF is an effective measure for objectively measuring the fatigue of television observers, including observers of binocular stereoscopic television. Also, the binocular stereoscopic television produced higher fatigue in observers than did the conventional television picture, but it was found that with respect to CFF viewing of around 30?min was allowable.