Visual discomfort whilst viewing 3D stereoscopic stimuli

3D stereoscopic technology intensifies and heightens the viewer s experience by adding an extra dimension to the viewing of visual content. However, with expansion of this technology to the commercial market concerns have been expressed about the potential negative effects on the visual system, producing viewer discomfort. The visual stimulus provided by a 3D stereoscopic display differs from that of the real world, and so it is important to understand whether these differences may pose a health hazard. The aim of this thesis is to investigate the effect of 3D stereoscopic stimulation on visual discomfort. To that end, four experimental studies were conducted. In the first study two hypotheses were tested. The first hypothesis was that the viewing of 3D stereoscopic stimuli, which are located geometrically beyond the screen on which the images are displayed, would induce adaptation changes in the resting position of the eyes (exophoric heterophoria changes). The second hypothesis was that participants whose heterophoria changed as a consequence of adaptation during the viewing of the stereoscopic stimuli would experience less visual discomfort than those people whose heterophoria did not adapt. In the experiment an increase of visual discomfort change in the 3D condition in comparison with the 2D condition was found. Also, there were statistically significant changes in heterophoria under 3D conditions as compared with 2D conditions. However, there was appreciable variability in the magnitude of this adaptation among individuals, and no correlation between the amount of heterophoria change and visual discomfort change was observed. In the second experiment the two hypotheses tested were based on the vergence-accommodation mismatch theory, and the visual-vestibular mismatch theory. The vergence-accommodation mismatch theory predicts that a greater mismatch between the stimuli to accommodation and to vergence would produce greater symptoms in visual discomfort when viewing in 3D conditions than when viewing in 2D conditions. An increase of visual discomfort change in the 3D condition in comparison with the 2D condition was indeed found; however the magnitude of visual discomfort reported did not correlate with the mismatch present during the watching of 3D stereoscopic stimuli. The visual-vestibular mismatch theory predicts that viewing a stimulus stereoscopically will produce a greater sense of vection than viewing it in 2D. This will increase the conflict between the signals from the visual and vestibular systems, producing greater VIMS (Visually- Induced Motion Sickness) symptoms. Participants did indeed report an increase in motion sickness symptoms in the 3D condition. Furthermore, participants with closer seating positions reported more VIMS than participants sitting farther away whilst viewing 3D stimuli. This suggests that the amount of visual field stimulated during 3D presentation affects VIMS, and is an important factor in terms of viewing comfort. In the study more younger viewers (21 to 39 years old) than older viewers (40 years old and older) reported a greater change in visual discomfort during the 3D condition than the 2D condition. This suggests that the visual system s response to a stimulus, rather than the stimulus itself, is a reason for discomfort. No influence of gender on viewing comfort was found. In the next experiment participants fusion capability, as measured by their fusional reserves, was examined to determine whether this component has an impact on reported discomfort during the watching of movies in the 3D condition versus the 2D condition. It was hypothesised that participants with limited fusional range would experience more visual discomfort than participants with a wide fusion range. The hypothesis was confirmed but only in the case of convergent and not divergent eye movement. This observation illustrates that participants capability to convergence has a significant impact on visual comfort. The aim of the last experiment was to examine responses of the accommodation system to changes in 3D stimulus position and to determine whether discrepancies in these responses (i.e. accommodation overshoot, accommodation undershoot) could account for visual discomfort experienced during 3D stereoscopic viewing. It was found that accommodation discrepancy was larger for perceived forwards movement than for perceived backwards movement. The discrepancy was slightly higher in the group susceptible to visual discomfort than in the group not susceptible to visual discomfort, but this difference was not statistically significant. When considering the research findings as a whole it was apparent that not all participants experienced more discomfort whilst watching 3D stereoscopic stimuli than whilst watching 2D stimuli. More visual discomfort in the 3D condition than in the 2D condition was reported by 35% of the participants, whilst 24% of the participants reported more headaches and 17% of the participants reported more VIMS. The research indicates that multiple causative factors have an impact on reported symptoms. The analysis of the data suggests that discomfort experienced by people during 3D stereoscopic stimulation may reveal binocular vision problems. This observation suggests that 3D technology could be used as a screening method to diagnose un-treated binocular vision disorder. Additionally, this work shows that 3D stereoscopic technology can be easily adopted to binocular vision measurement. The conclusion of this thesis is that many people do not suffer adverse symptoms when viewing 3D stereoscopic displays, but that if adverse symptoms are present they can be caused either by the conflict in the stimulus, or by the heightened experience of self-motion which leads to Visually-Induced Motion Sickness (VIMS)

Dynamic horizontal image translation in stereo 3D

Im Bereich Stereo 3D (S3D) bezeichnet „Dynamic Horizontal Image Translation (DHIT)“ das Prinzip, die S3D-Ansichten einer Szene horizontal in entgegengesetzte Richtungen zu verschieben, wodurch die dargestellte Szene in der Tiefe verschoben wird. Dies wird vor allem im Kontext von „Active Depth Cuts“ eingesetzt. Hier werden die S3D-Ansichten vor und nach einem Szenenschnitt so verschoben, dass es nicht zu starken, störenden Tiefensprüngen kommt. Die menschliche Wahrnehmung der DHIT wurde experimentell untersucht. Eine der wichtigsten Erkenntnisse war, dass es starke individuelle Unterschiede in der Empfindlichkeit gegenüber der DHIT gibt. Daher wird empfohlen die Verschiebungsgeschwindigkeit einer S3D-Ansicht nicht höher als 0,10 °/s bis 0,12 °/s zu wählen, sodass Zuschauerinnen und Zuschauer nicht von der DHIT gestört werden. Bei der DHIT kommt es zu einer Verzerrung der dargestellten Szenentiefe. Dies wird bei dem vorgeschlagenen Ansatz „Distortion-Free Dynamic Horizontal Image Translation (DHIT+)“ kompensiert, indem der Abstand zwischen den S3D-Kameras durch Verfahren der Ansichtensynthese angepasst wird. Dieser Ansatz zeigte sich signifikant weniger störend im Vergleich zur DHIT. Die Ansichten konnten ohne Wahrnehmungsbeeinträchtigung etwa 50% schneller verschoben werden. Ein weiteres vorgeschlagenes Verfahren ist „Gaze Adaptive Convergence in Stereo 3D Applications (GACS3D)“. Unter Verwendung eines Eyetrackers wird die Disparität des geschätzten Blickpunkts langsam über die DHIT reduziert. Dies soll die Ermüdung des visuellen Systems mindern, da die Diskrepanz zwischen Akkommodation und Konvergenz reduziert wird. In einem Experiment mit emuliertem Eye-Tracking war GACS3D signifikant weniger störend als eine normale DHIT. Im Vergleich zwischen dem kompletten GACS3D-Prototypen und einer Bildsequenz ohne jegliche Verschiebungen konnte jedoch kein signifikanter Effekt auf den subjektiven Betrachterkomfort registriert werden. Eine Langzeituntersuchung der Ermüdung des visuellen Systems ist nötig, was über den Rahmen dieser Dissertation hinausgeht. Da für GACS3D eine hochgenaue Schätzung der Blickpunktdisparität benötigt wird, wurde die „Probabilistic Visual Focus Disparity Estimation“ entwickelt. Bei diesem Ansatz wird die 3D-Szenenstruktur in Echtzeit geschätzt und dazu verwendet, die Schätzung der Blickpunktdisparität deutlich zu verbessern.Dynamic horizontal image translation (DHIT) denotes the act of dynamically shifting the stereo 3D (S3D) views of a scene in opposite directions so that the portrayed scene is moved along the depth axis. This technique is predominantly used in the context of active depth cuts, where the shifting occurs just before and after a shot cut in order to mitigate depth discontinuities that would otherwise induce visual fatigue. The perception of the DHIT was investigated in an experiment. An important finding was that there are strong individual differences in the sensitivity towards DHIT. It is therefore recommended to keep the shift speed applied to each S3D view in the range of 0.10 °/s to 0.12 °/s so that nobody in the audience gets annoyed by this approach. When a DHIT is performed, the presented scene depth is distorted, i.e., compressed or stretched. A distortion-free dynamic horizontal image translation (DHIT+) is proposed that mitigates these distortions by adjusting the distance between the S3D cameras through depth-image-based rendering techniques. This approach proved to be significantly less annoying. The views could be shifted about 50% faster without perceptual side effects. Another proposed approach is called gaze adaptive convergence in stereo 3D applications (GACS3D). An eye tracker is used to estimate the visual focus whose disparity is then slowly reduced using the DHIT. This is supposed to lessen visual fatigue since the infamous accommodation vergence discrepancy is reduced. GACS3D with emulated eye tracking proved to be significantly less annoying than a regular DHIT. In a comparison between the complete prototype and a static horizontal image translation, no significant effect on subjective visual discomfort could be observed, however. A long-term evaluation of visual fatigue is necessary, which is beyond the scope of this work. In GACS3D, highly accurate visual focus disparity is required. Therefore, the probabilistic visual focus disparity estimation (PVFDE) was developed, which utilizes a real-time estimation of the 3D scene structure to improve the accuracy by orders of magnitude compared to commonly used approaches

Perceived Depth Control in Stereoscopic Cinematography

Despite the recent explosion of interest in the stereoscopic 3D (S3D) technology, the ultimate prevailing of the S3D medium is still significantly hindered by adverse effects regarding the S3D viewing discomfort. This thesis attempts to improve the S3D viewing experience by investigating perceived depth control methods in stereoscopic cinematography on desktop 3D displays. The main contributions of this work are: (1) A new method was developed to carry out human factors studies on identifying the practical limits of the 3D Comfort Zone on a given 3D display. Our results suggest that it is necessary for cinematographers to identify the specific limits of 3D Comfort Zone on the target 3D display as different 3D systems have different ranges for the 3D Comfort Zone. (2) A new dynamic depth mapping approach was proposed to improve the depth perception in stereoscopic cinematography. The results of a human-based experiment confirmed its advantages in controlling the perceived depth in viewing 3D motion pictures over the existing depth mapping methods. (3) The practicability of employing the Depth of Field (DoF) blur technique in S3D was also investigated. Our results indicate that applying the DoF blur simulation on stereoscopic content may not improve the S3D viewing experience without the real time information about what the viewer is looking at. Finally, a basic guideline for stereoscopic cinematography was introduced to summarise the new findings of this thesis alongside several well-known key factors in 3D cinematography. It is our assumption that this guideline will be of particular interest not only to 3D filmmaking but also to 3D gaming, sports broadcasting, and TV production

EVALUATION OF VISUALLY INDUCED MOTION SICKNESS CAUSED BY VIEWING OF 3D STEREOSCOPY USING ELECTROENCEPHALOGRAPHY TECHNIQUE

The 3D movies are attracting the viewers as they see objects flying out of the screen. However, many viewers reportof problems that they face after watching 3D movies. Visual fatigue, eye strain, headaches, dizziness, blurred vision or in other words, Visually Induced Motion Sickness (VIMS) are reported by viewers of 3D movies. In this thesis, we aim to compare a 3D passive technology with a conventional 2D technology to find whether 3D is causing trouble in the viewers or not

Toward 3D integral-imaging broadcast with increased viewing angle and parallax

We propose a new method for improving the observer experience when using an integral monitor. Our method permits to increase the viewing angle of the integral monitor, and also the maximum parallax that can be displayed. Additionally, it is possible to decide which parts of the 3D scene are displayed in front or behind the monitor. Our method is based, first, in the direct capture, with significant excess of parallax, of elemental images of 3D real scenes. From them, a collection of microimages adapted to the observer lateral and depth position is calculated. Finally, an eye-tracking system permits to determine the 3D observer position, and therefore to display the adequate microimages set. Summarizing, it is reported here, for the first time we believe, the application of eye-tracking technology to the display of integral images of 3D real scenes with bright background. Although we are reporting here only a proof-of-concept experiment, this result could have direct application in a close future for the broadcasting of 3D videos recorded in professional studio, for videoconferences or for on-line professional meetings

The Mark 3 Haploscope

A computer-operated binocular vision testing device was developed as one part of a system designed for NASA to evaluate the visual function of astronauts during spaceflight. This particular device, called the Mark 3 Haploscope, employs semi-automated psychophysical test procedures to measure visual acuity, stereopsis, phoria, fixation disparity, refractive state and accommodation/convergence relationships. Test procedures are self-administered and can be used repeatedly without subject memorization. The Haploscope was designed as one module of the complete NASA Vision Testing System. However, it is capable of stand-alone operation. Moreover, the compactness and portability of the Haploscope make possible its use in a broad variety of testing environments

A Neurophysiologic Study Of Visual Fatigue In Stereoscopic Related Displays

Two tasks were investigated in this study. The first study investigated the effects of alignment display errors on visual fatigue. The experiment revealed the following conclusive results: First, EEG data suggested the possibility of cognitively-induced time compensation changes due to a corresponding effect in real-time brain activity by the eyes trying to compensate for the alignment. The magnification difference error showed more significant effects on all EEG band waves, which were indications of likely visual fatigue as shown by the prevalence of simulator sickness questionnaire (SSQ) increases across all task levels. Vertical shift errors were observed to be prevalent in theta and beta bands of EEG which probably induced alertness (in theta band) as a result of possible stress. Rotation errors were significant in the gamma band, implying the likelihood of cognitive decline because of theta band influence. Second, the hemodynamic responses revealed that significant differences exist between the left and right dorsolateral prefrontal due to alignment errors. There was also a significant difference between the main effect for power band hemisphere and the ATC task sessions. The analyses revealed that there were significant differences between the dorsal frontal lobes in task processing and interaction effects between the processing lobes and tasks processing. The second study investigated the effects of cognitive response variables on visual fatigue. Third, the physiologic indicator of pupil dilation was 0.95mm that occurred at a mean time of 38.1min, after which the pupil dilation begins to decrease. After the average saccade rest time of 33.71min, saccade speeds leaned toward a decrease as a possible result of fatigue on-set. Fourth, the neural network classifier showed visual response data from eye movement were identified as the best predictor of visual fatigue with a classification accuracy of 90.42%. Experimental data confirmed that 11.43% of the participants actually experienced visual fatigue symptoms after the prolonged task