Simultaneous measurement of lens accommodation and convergence in natural and artificial 3D vision

Recent advances in 3D technology have been accompanied by increasing complaints of visual fatigue. The usual explanation for such fatigue is that accommodation and convergence are mismatched during stereoscopic vision. The aim of this study was to measure fixation distances between lens accommodation and convergence in young subjects while they viewed real objects and 3D video clips. Measurements were made using an original instrument. The 3D video clips were presented to subjects using a liquid crystal shutter glass system. The results showed that when viewing real objects, the diopter values of subjects' accommodation and convergence were similar and changed periodically. This measurement method was thus considered to be appropriate for the measurement of stereoscopic vision. We also investigated lens accommodation and convergence when subjects viewed 3D video clips. Both accommodation and convergence were found to move along with the virtual position of 3D video clips. Therefore, there was little discrepancy between accommodation and convergence during the viewing of 3D images.     

Interaction and visual performance in stereoscopic displays: A review

In this paper, authors systematically selected and reviewed articles related to stereoscopic displays and their advances, with a special focus on perception, interaction, and corresponding challenges. The aim was to understand interaction‐related problems, provide possible explanations, and identify factors that limit their applications. Despite promising advancements, there are still issues that researchers in the field fail to explain precisely. The two major problems in stereoscopic viewing are, compared with the real world, objects are perceived to be smaller than they actually are and there are discomfort and visual syndromes. Furthermore, there is general agreement that humans underestimate their egocentric distance in a virtual environment (VE). Our analysis revealed that in the real world, distance estimation is about 94% accurate, but in VE, it is only about 80% accurate. This problem could reduce the efficacy of different sensory motor‐based applications where interaction is important. Experts from human factors, computing, psychology, and others have studied contributing factors such as types of perception/response method, quality of graphics, associated stereoscopic conditions, experience in virtual reality (VR), and distance signals. This paper discusses the factors requiring further investigation if the VR interaction is to be seamlessly realized. In addition, engineering research directions aiming at improving current interaction performances are recommended.     

Utility of stereoscopic displays for indirect-vision driving and robot teleoperation

The effectiveness of an active shutter-glasses stereoscopic display (SD) and a passive polarised SD was evaluated in a live robot-teleoperation task and a simulated indirect-vision driving task in various terrains. Overall, participants completed their tasks significantly faster with the SDs in three-dimensional (3D) mode than with the SDs in the baseline 2D mode. They also navigated more accurately with the SDs in 3D mode. When the effectiveness of the two types of SDs was examined separately, results showed that the active shutter-glasses SD resulted in faster responses and task completion times than the passive polarised SD, though most of the differences failed to reach statistical significance. Perceived workload when interacting with the two SD systems did not differ significantly between the active versus passive display types or between the 3D and 2D modes of operation; however, participants reported more severe discomfort after interacting with the passive polarised SD.     

Visual comfort in 2D/3D modes of glasses‐type stereoscopic displays

In this study, we compared visual comfort in 2D/3D modes of the pattern retarder (PR) and shutter glasses (SG) stereoscopic displays by changing viewing factors and image contents. The viewing factors include ambient illuminance/monitor luminance/background luminance and image contents mainly are determined with different disparity limits. The degrees of 2D/3D visual comfort were investigated by using various combinations of ambient illuminance, monitor luminance, background luminance, and disparity limit. A series of psychological experiments were also performed to compare 2D and 3D viewing experiences for the passive PR and active SG stereoscopic displays and to discover more comfortable conditions under various variable combinations. The experiment results show that the various variable combinations affecting visual comfort in the passive PR and active SG stereoscopic displays were significantly different. Finally, we suggest more comfortable conditions of viewing 2D and 3D images for the PR and SG stereoscopic displays.     

A study on the perceptual relevance of crosstalk equations for stereoscopic displays

Although several crosstalk definitions have been proposed to indicate the level of crosstalk in stereoscopic displays, they do not necessarily correlate with perceived crosstalk. Based on two perception experiments, with each a different approach, we studied the correspondence between 10 objective crosstalk equations and perceived crosstalk. The first experiment, in which the crosstalk level was evaluated, demonstrates that crosstalk equations based on Weber's law (ΔL/L) show the highest correlation with perceived crosstalk for the most critical case, that is, a center circle in an outer disc. A second experiment, based on crosstalk visibility thresholds, supported that crosstalk equations based on Weber's law show the highest correspondence with human perception.     

Exploring crosstalk perception for stereoscopic 3D head‐up displays in a crosstalk simulator

In today's upper class vehicles, head‐up displays (HUDs) are state of the art human–machine interfaces used to increase driving security and comfort. Working with a stereoscopically perceived viewing impression, a novel automotive 3D HUD would allow the simultaneous visualization of multiple contents in various depth planes. However, stereoscopic crosstalk is one of the most important parameters influencing the image quality of stereoscopic systems. We present a setup to simulate crosstalk including a specific software solution. It constitutes a platform to explore the effects of stereoscopic crosstalk in the augmented reality viewing conditions of a 3D HUD. As the setup allows the variation of numerous parameters, it provides a versatile research platform. By means of it, we investigate the variation of the visibility and acceptability thresholds of crosstalk over various parameters. Our results include the finding that they decrease with rising contrast affirming this behavior known for conventional stereoscopic displays for stereoscopic see‐through displays.     

User experience while viewing stereoscopic 3D television

3D display technologies have been linked to visual discomfort and fatigue. In a lab-based study with a between-subjects design, 433 viewers aged from 4 to 82 years watched the same movie in either 2D or stereo 3D (S3D), and subjectively reported on a range of aspects of their viewing experience. Our results suggest that a minority of viewers, around 14%, experience adverse effects due to viewing S3D, mainly headache and eyestrain. A control experiment where participants viewed 2D content through 3D glasses suggests that around 8% may report adverse effects which are not due directly to viewing S3D, but instead are due to the glasses or to negative preconceptions about S3D (the ‘nocebo effect’). Women were slightly more likely than men to report adverse effects with S3D. We could not detect any link between pre-existing eye conditions or low stereoacuity and the likelihood of experiencing adverse effects with S3D.     

Visual comfort enhancement study based on visual attention detection for stereoscopic displays

Although numerous potential causes may lead to visual discomfort when viewing content on three‐dimensional (3D) displays, vergence–accommodation conflict is a particular cause of binocular parallax‐based stereoscopic displays, and it is unavoidable. Based on the study of 3D content visual attention, we proposed a novel stereoscopic depth adjustment method to improve the visual comfort and enhance perceived naturalness. The proposed method combined the 3D image saliency and specific viewing condition to establish a novel model for computing the optimum zero‐disparity plane of stereoscopic image. The results of perception experiments, focused on visual comfort and stereoscopic sensation, supported that the proposed method can significantly enhance stereoscopic viewing comfort and even can improve the stereoscopic sensation by insuring the 3D image fusion.     

A crosstalk model and its application to stereoscopic and autostereoscopic displays

We propose a model to quantify the crosstalk phenomenon for stereoscopic and autostereoscopic displays, separate crosstalk contributed from co‐location image contrast (CIC) and system crosstalk (SCT), introduce gray scale dependency of CIC, modify model for gray scale dependency of SCT in active type 3D displays, and apply the model to derive the 3D luminance and SCT measurement formulas. The model might serve as a basis for the 3D metrology, and the results of this research should be of reference value to hardware makers and inspectors of stereoscopic and autostereoscopic displays.     

基于Java3D的立体显示技术及其在仿真中的应用

提出用虚拟环境建模API Java3D产生场景左右眼图像的关键技术,以及用Java3D如何控制影响立体显示效果的主要因素,这些主要因素是左右图像视差、虚拟眼睛视场宽度和虚拟眼睛到显示平面的距离。这些技术已成功应用于Java3D开发的汽车驾驶仿真系统中以实现立体显示。这些技术为用Java3D开发视景仿真系统和三维立体视觉游戏软件提供支持。     

基于矩阵变换的立体视频播放技术研究

立体图像按存储方式不同分为立体图片和视频,把左右格式立体图像准确传输到裸眼3D显示器的亚屏幕,是3D播放的关键技术。针对不同存储格式的立体图像,使用矩阵变换及视频融合算法,在FFmpeg函数库基础上构建立体视频播放器。实验表明该算法能将立体图像正确映射到左右眼亚屏幕。     

Measurement of minimum angle of resolution (MAR) in the stereoscopic display using the optotype of stereoscopic stimuli

In stereoscopic images, the crossing point of the viewing directions of the two eyes determines the perceived depth. Assuming that accommodation is affected by the positions of the crossing point, the effect of crossing point on minimum angle of resolution (MAR) was investigated. For 40 participants, MAR was measured by two‐alternative forced choice where Snellen optotype E of up and down directions were used as two kinds of stimuli. As the crossing point of the viewing direction of the left and right eyes moves farther from the sample display, the ability to identify the direction of letter E decreases at the optotype of the same line thickness. The change of MAR shows linear trends with respect to the optical power change that are the reciprocal of the distance from the participant to the crossing points located out of screen and on screen.     

Clinical applications for stereoscopic 3‐D displays

Abstract— Stereoscopic 3‐D digital imaging holds the promise of improving the detection, diagnosis, and treatment of disease as well as enhancing the training and preparation of medical professionals through use of stereoscopic 3‐D displays in concert with the many volumetric visualization techniques/modalities developed in recent years. While so‐called 3‐D graphics have improved the state of computer visualization in general, 3‐D displays make full use of the human‐visual perception, and thus can provide critical insight in complex computer‐generated and video 3‐D data. The stereo 3‐D applications reviewed in this paper include screening of breast cancer and diabetic retinopathy, visualization for minimally invasive surgery, and the teaching of anatomy. Also included is a discussion of ground‐breaking results from a stereo digital mammography clinical trial under way at Emory University.     

Motion artifacts on 240‐Hz OLED stereoscopic 3D displays

Temporal multiplexing is a popular approach for presenting different images to the two eyes in stereoscopic 3D (S3D) displays. We examined the visibility of flicker and motion artifacts—judder, motion blur, and edge banding—on a 240‐Hz temporally multiplexed S3D OLED display. Traditionally, a frame rate of 120 Hz (60 Hz per eye) is used to avoid visible flicker, but there is evidence that higher frame rates provide visible benefits. In a series of psychophysical experiments, we measured the visibility of artifacts on the OLED display using temporal multiplexing and those of a 60‐Hz S3D LCD using spatial multiplexing. We determined the relative contributions of the frame rate of the content, update rate of the display, duty cycle, and number of flashes. We found that short duty cycles and low flash numbers reduce the visibility of motion artifacts, while long duty cycles and high flash numbers reduce flicker visibility.     

Stereoscopic 3‐D display with optical correction for the reduction of the discrepancy between accommodation and convergence

Abstract— This paper describes a method for reducing the discrepancy between accommodation and convergence when viewing stereoscopic 3‐D images. The method uses a newly developed stereoscopic 3‐D display system with a telecentric optical system and a mobile LCD. The examination of a mono‐focal lens showed that a correction lens having the appropriate refractive power and conditions for presenting stereoscopic 3‐D images clearly reduces the discrepancy between accommodation and convergence. The authors also developed a stereoscopic 3‐D display that uses dynamic optical correction to reduce the discrepancy between accommodation and convergence. The display equalizes the theoretical points of accommodation and convergence. The purpose of the development was to expand the regeneration range of a stereoscopic 3‐D image having the appropriate accommodation. An evaluation of the developed display showed that it resolves the discrepancy between convergence and accommodation.     

Ergonomic evaluation of interaction techniques and 3D menus for the practical design of 3D stereoscopic displays

There has been a recent commercialization of 3D stereoscopic displays in order to implement them in a virtual reality environment. However, there is a lack of extensive research into user interfaces for 3D applications on stereoscopic display. This study focused on three representative interaction techniques (ray-casting, keypad and hand-motion techniques) utilizing a head-mounted display and 3D CAVE. In addition, the compatibility with 3D menus was also investigated based on performance and subjective assessment. Nine 3D menus were designed for the experiment in regards to three 2D metaphors (pop-up, pull-down and stack menus) and three structural layouts (list, cubic and circular menus). The most suitable technique for the 3D user interface on a stereoscopic display was the ray-casting technique and the stack menu which provided the user with good performance and subjective response. In addition, it was found that the cubic menu was not as effective as other menus when used with the three interaction techniques.Relevance to industryThis research describes a distinctive evaluation method and recommendations that guarantee the suitability for interactive 3D environments. Therefore, the results will encourage practitioners and researchers that are new to the area of 3D interface design.     

Characterizing crosstalk in anaglyphic stereoscopic images on LCD monitors and plasma displays

Abstract— In 1853, William Rollman developed the inexpensive and easy to use anaglyph method for displaying stereoscopic images. Although it can be used with nearly any type of full‐color display, the anaglyph method compromises the accuracy of color reproduction, and it often suffers from crosstalk (or ghosting) between the left‐ and right‐eye image channels. Crosstalk degrades the ability of the observer to fuse the stereoscopic image, and hence reduces the quality of the 3‐D image. Crosstalk is present in various levels with most stereoscopic displays; however, it is often particularly evident with anaglyphic 3‐D images. This paper summarizes the results of two projects that characterized the presence of anaglyphic crosstalk due to spectral issues on 13 LCD monitors, 14 plasma displays, and a CRT monitor when used with 25 different pairs of anaglyph 3‐D glasses. A mathematical model was used to predict the amount of crosstalk in anaglyphic 3‐D images when different combinations of displays and glasses are used, and therefore highlight displays, glasses, and combinations thereof which exhibit lower levels of crosstalk when displaying anaglyphic 3‐D images.     

True 3‐D scanned voxel displays using single or multiple light sources

Abstract— Conventional stereoscopic displays require viewers to unnaturally keep eye accommodation fixed at one focal distance while they dynamically change vergence to view objects at different distances. This forced decoupling of reflexively linked processes fatigues eyes, causes discomfort, compromises image quality, and may lead to pathologies in developing visual systems. Volumetric displays can overcome this conflict, but only for small objects placed within a limited range of viewing distances and accommodation levels, and cannot render occlusion cues correctly. Our multi‐planar True 3‐D displays generate accommodation cues that match vergence and stereoscopic retinal disparity demands and can display images and objects at viewing distances throughout the full range of human accommodation (from 6.25 cm to infinity), better mimicking natural vision and minimizing eye fatigue.     

Motion parallax from head movement enhances stereoscopic displays by improving presence and decreasing visual fatigue

Virtual reality has advanced significantly recent years. Public attention and most academic studies of late have centered on head-worn VR. However, there are other VR modalities, and different modalities may be suitable in different situations. In this paper, we investigate Fish Tank Virtual Reality (FTVR) systems, which is close to readiness to be part of our everyday lives. In particular, stereoscopic displays and head tracking systems, some of the most important hardware components of FTVR systems, are now widespread commodities. This means that FTVR may soon become a platform for everyday applications. However, further understanding of the capabilities, limitations, and human factors of FTVR systems using modern commodity hardware is critical to the adoption of FTVR. Since one of the most important aspects of a FTVR system is how well it provides a sense of presence to users, we present a study that explores the role of motion parallax when combined with stereopsis in a FTVR system. We measure fatigue and subjective perception of presence using standard questionnaires. We find that users receiving both cues have lower visual fatigue and higher ratings for presence than those receiving stereo cues only. Measurements of participants’ head movement during each task prove valuable in explaining the experimental findings. We conclude that motion parallax is important for enhancing user experience by lowering visual fatigue and increasing users’ subjective perception of presence.     

Experimental determination of the range of binocular disparity for which stereoscopic fusion occurs at a viewing distance of 2.5 m for a stereoscopic TV

The threshold for binocular disparity for which a participant can observe a clear stereoscopic image on a 3D TV using Patterned Retarder technology and polarizing eyeglasses is determined for a viewing distance of 2.5 m. An optotype, the letter “m” with a line thickness of 1.08 mm in the upward or downward direction, was used as the stereoscopic stimulus. Under the measurement conditions of the increase and decrease of binocular disparity of the stereoscopic stimulus, the binocular disparity thresholds for 40 participants were measured for the horizontal direction. Most of the participants were in their twenties. The thresholds were measured to be slightly larger for the condition of increasing binocular disparity compared with the condition of decreasing binocular disparity. Personal differences were measured to be noticeable.