3D Visual Fatigue Research Articles

27‐3: Invited Paper: Visual Fatigue‐free AR Displays

AR enables the integration of virtual digital information on the real world. However, most AR displays suffer from accommodation vergence conflict, which results in 3D visual fatigue. In this work, our works on 3D visual fatigue‐free display techniques would be presented.

7.2: Invited Paper: Vari‐focal Near‐eye Displays Based on Geometry Phase Liquid Crystal Lenses

The development of metaverse has the potential to revolutionize people's life. As the entry to metaverse, virtual reality (VR) and augmented reality (AR) technologies are gaining ever‐increasing attention. However, there is vergence‐accommodation conflict problem for most VR or AR 3D displays. In this paper, we propose to realize vari‐focal near‐eye displays based on tunable geometry phase liquid crystal lenses to address this problem. Experimental results validate that images can be rendered at different depth as the tunable lenses change their focal lengths. Thus, correct accommodation cue can be induced, and 3D visual fatigue could be significantly suppressed.

Planar Alvarez tunable lens based on polymetric liquid crystal Pancharatnam-Berry optical elements.

Virtual reality (VR) and augmented reality (AR) have widespread applications. The vergence-accommodation conflict (VAC), which causes 3D visual fatigue, has become an urgent challenge for VR and AR displays. Alvarez lenses, with precise and continuously tunable focal length based on the lateral shift of its two sub-elements, are a promising candidate as the key electro-optical component in vari-focal AR display systems to solve the VAC problem. In this paper, we propose and fabricate a compact Alvarez lens based on planar polymetric liquid crystal Pancharatnam-Berry optical elements. It can provide continuous diopter change from -1.4 D to 1.4 D at the wavelength of 532 nm with the lateral shift ranging from -5 mm to 5 mm. We also demonstrate an AR display system using this proposed Alvarez lens, where virtual images are augmented on the real world at different depths.

16‐3: Compact Tunable Alvarez Lens Based on Pancharatnam‐Berry Optical Elements

Alvarez lens, whose focal length can be continuously tuned by changing the relative lateral positions of its sub‐elements, holds promise in realizing vari‐ or multi‐focal augmented reality (AR) displays to eliminate vergence‐accommodation conflict and 3D visual fatigue. In this paper, we propose and realize a compact Alvarez lens based on planar Pancharatnam‐Berry optical elements. We also demonstrate an augmented reality display system using the proposed Alvarez lens, which allows virtual objects to appear at different focal depths.

Investigate the 3D Visual Fatigue Using Modified Depth-Related Visual Evoked Potential Paradigm.

Prolonged viewing of 3D content may result in severe fatigue symptoms, giving negative user experience thus hindering the development of 3D industry. For 3D visual fatigue evaluation, previous studies focused on exploring the changes of frequency-domain features in EEG for various fatigue degrees. However, their time-domain features were scarcely investigated. In this study, a modified paradigm with a random disparities order is adopted to evoke the depth-related visual evoked potentials (DVEPs). Then the characteristics of the DVEPs components for various fatigue degrees are compared using one-way repeated-measurement ANOVA. Point-by-point permutation statistics revealed sample points from 100ms to 170ms - including P1 and N1 - in sensors Pz and P4 changed significantly with visual fatigue. More specifically, we find that the amplitudes of P1 and N1 change significantly when visual fatigue increases. Additionally, independent component analysis identify P1 and N1 which originate from posterior cingulate cortex are associated statistically with 3D visual fatigue. Our results indicate there is a significant correlation between 3D visual fatigue and P1 amplitude, as well as N1, of DVEPs on right parietal areas. We believe the characteristics (e.g., amplitude and latency) of identified components may be the indicators of 3D visual fatigue evaluation. Furthermore, we argue that 3D visual fatigue may be associated with the activities decrease of the attention and the processing capacity of disparity.

Investigating the neural activity of various 3D visual fatigue degrees using depth‐related visual evoked potentials

AbstractSevere visual fatigue symptoms occur while users view three‐dimensional (3D) content. These symptoms adversely affect the user experience and hinder the widespread application of 3D media. Existing studies mainly used electroencephalography (EEG) power (based on frequency domain analysis) to evaluate 3D visual fatigue (3DVF), but their results were often contradictory and confusing. To address this problem, we investigated the relationship between EEG features and visual fatigue from the perspective of both time and time‐frequency domain. Random‐dot stereograms (RDS) with various disparities were employed to elicit depth‐related visual evoked potentials (VEPs). The experiment lasted about 27 min for each subject to induce fatigue, and the EEG was recorded synchronously. VEPs of different fatigue levels were processed to extract both time (such as P120 and N170 components in VEPs) and time‐frequency (like event‐related spectral perturbation [ERSP]) domain characteristics. A significant increase in P120 amplitude was observed in the parietal region, and time‐frequency analysis also revealed a significant ERSP decrease of theta bands in the central‐frontal region with a latency of 200 to 300 ms when subjects suffered fatigue. Our results confirm the hypothesis that activity of theta decreased with 3DVF level, or rather, we found ERSPs of theta bands on FC4 and Cz in the 200‐ to 300‐ms window decreased significantly across four fatigue levels. Furthermore, we first reported the relationship between P120 amplitude and 3DVF, which implied this feature could be considered as a feature of 3DVF evaluation. In summary, our studies could provide a new insight for 3DVF evaluation using EEG.

Research on the effect of contrast enhancement and illumination condition on 3D visual fatigue

Abstract3D visual comfort can be influenced by such common factors as binocular parallax, 3D image contrast, viewing distance, and illumination condition. This paper investigates the effect of contrast enhancement and illumination condition on 3D visual fatigue by performing a visual fatigue measurement experiment, of which subjects need to watch 3D images under two illumination conditions and finish a comfort judgment task. The proportion of discomfort images, the subjective evaluation of visual fatigue under 100 lux and 500 lux illumination conditions, the effect of image contrast enhancement on 3D visual fatigue, and the relationship between visual fatigue and proportion of discomfort images were analyzed, respectively. The experimental results showed that both the contrast enhanced by Laplacian algorithm and low illumination condition have positive influence on 3D visual perception of eyes; the 3D visual fatigue of contrast enhanced by Laplacian algorithm under low illumination condition was less than other situations in the experiment. Moreover, it was examined that the proportion of discomfort images can be potential prediction indicator of the 3D visual fatigue.

IR-camera-based measurements of 2D/3D cognitive fatigue in 2D/3D display system using task-evoked pupillary response.

This study was carried out to evaluate a method used to measure three-dimensional (3D) cognitive fatigue based on the pupillary response. This technique was designed to overcome measurement burdens by using non-contact methods. The pupillary response is related to cognitive function by a neural pathway and may be an indicator of 3D cognitive fatigue. Twenty-six undergraduate students (including 14 women) watched both 2D and 3D versions of a video for 70min. The participants experienced visual fatigue after viewing the 3D content. Measures such as subjective rating, response time, event-related potential latency, heartbeat-evoked potential (HEP) alpha power, and task-evoked pupillary response (TEPR) latency were significantly different. Multitrait-multimethod matrix analysis indicated that HEP and TEPR latency measures had stronger reliability and higher correlations with 3D cognitive fatigue than other measures. TEPR latency may be useful for quantitatively determining 3D visual fatigue, as it can be easily used to evaluate 3D visual fatigue using a non-contact method without measuring burden.

This Issue of ACTA

This Issue of ACTA

The correlation between visual fatigue and duration of viewing as assessed by brain monitoring

AbstractDuration of viewing was considered as one of the most important factors of 3D visual fatigue. However, their relationship was not well studied. We proposed to use brain monitoring techniques to reveal more details about the variety of brain activity while watching three‐dimensional (3D) content. We investigated the spectral patterns in the electroencephalogram related to various duration of viewing and showed the power spectral density varied significantly along with the development of fatigue over occipital lobe, parietal lobe, and right frontal lobe. Moreover, we first described the trend of brain activity during 3D content viewing and revealed the location of significant components related to 3D visual fatigue. We believe that the absolute power describes more information and may be a better indicator of 3D visual fatigue assessment compared with relative power. We also first revealed the cortex location that is related to 3D visual fatigue. Our findings may help to define appropriate electroencephalogram features for online 3D visual fatigue detection while participants viewing 3D content.

Probabilistic assessment of visual fatigue caused by stereoscopy using dynamic Bayesian networks.

In this article, we develop a dynamic Bayesian network (DBN) model to measure 3D visual fatigue. As far as our information goes, this is the first adaptation of a DBN structure-based probabilistic framework for inferring the 3D viewer's state of visual fatigue. Our measurement focuses on the interdependencies between each factor and the phenomena of visual fatigue in stereoscopy. Specifically, the implementation of DBN with using multiple features (e.g. contextual, contactless and contact physiological features) and dynamic factor provides a systematic scheme to evaluate 3D visual fatigue. In contrast to measurement results between the mean opinion score (MOS) and Bayesian network model (with static Bayesian network and DBN), the visual fatigue in stereoscopy at time slice t is influenced by a dynamic factor (time slice t-1). In the presence of dynamic factors (time slice t-1), our proposed measuring scheme based on DBN is more comprehensive. (i) We cover more features for inferring the visual fatigue, more reliably and accurately; (ii) at different time slices, the dynamic factor features are significant for inferring the visual fatigue state of stereoscopy.

Study of objective parameters of 3D visual fatigue based on analysis of salient area

Visual fatigue of 3D display restricts its wide application, moreover, human attention is one of important factors for visual fatigue due to the fact that perceptual salient regions determine the quality of experience of 3D contents. In order to study the relationship between 3D image salient area and 3D visual fatigue, an experiment is designed in which subjects are required to accomplish a task realized with 3D display system, eye tracking system and ECG detecting apparatuses. The aim of the task is to induce 3D visual fatigue with stimuli with different salient areas. ECG signals and eye tracking parameters are recorded during the whole process and the questionnaire is adopted to obtain the subjective fatigue parameters. Analysis of the experimental data shows the relationship between salient area and visual fatigue. In our research, an evaluation method of visual fatigue by considering both ECG signals and eye tracking parameters is developed, and a visual fatigue evaluation model based on salient area of 3D images is introduced. In our future study, more elements will be added into the experiment to find more factors which can induce 3D visual fatigue.

Criterion Suggestion on Relative Disparity, Viewing Distance and Viewing Angle to Minimize 3D Visual Fatigue for Pattern-Retarded Type 3D Display

Criterion Suggestion on Relative Disparity, Viewing Distance and Viewing Angle to Minimize 3D Visual Fatigue for Pattern-Retarded Type 3D Display

Visual Fatigue during Continuous Viewing the 3D Movie

Three-dimensional (3D) displays become more and more popular in many fields. However, visual fatigue is one of the critical factors that impede the wide range of applications of 3D technology. Although many studies have investigated the 3D visual fatigue, a few of them are based on continuous viewing 3D contents. In this paper, we propose a method to evaluate visual fatigue through subjective scoring and objective measuring the physiological parameters during the continuous viewing 3D/2D movie. In the viewing, we test the objective and subjective indicators, including the heart rate (HR), blink frequency (BF) and percentage of eyelid closure over the pupil over time (PERCLOS) and the subjective scoring (SS). Before and after viewing the video, VRT, PMA and questionnaires are measured. Experimental results showed that the subjective score and objective indicates of visual fatigue increased gradually with viewing time although it was fluctuated. The symptoms of visual fatigue were generally more serious after viewing 3D movie than 2D ones. Based on the results above, a model was built to predict visual fatigue from HR and BF during continuous viewing 3D video processes.

The Research of Depth Discontinuity Detection Using Adaptive DIP

Depth discontinuities are the layers of the world and is used to track object, image retrieval, evaluation of the 3D visual fatigue. To extract depth discontinuities from disparity map, we adopt DIP operator that is the difference of inverse probabilities for extracting sketch features that contain valleys and edges in 2D image. However, DIP needs a threshold to determine depth discontinuities and this is threshold needs user interaction. In this paper, we propose the method that extracts depth discontinuities without user interaction using learned threshold. We learned the threshold with the Middlebury disparity maps and made the evaluation to decide the threshold.

11.4: Study on the Saccadic Eye Movement Metric of Visual Fatigue Induced By 3D Displays

Developing a valid measurement of visual fatigue induced by 3D display remains a big challenge and is beneficial for optimizing the system design. In this paper, effects of 3D visual fatigue on the dynamics of saccadic eye movements are examined. Thirteen subjects participate in a random dot stereogram (RDS) based task, the performing of the task by the subjects is assumed to directly influence the level of visual fatigue that is evaluated using subjective ratings, optometric tests and eye movement indices. The results of critical fusion frequency (CFF) and accommodation measurement (ACC) show that the proposed experiment setup can induce visual fatigue. According to the subjective ratings, the visual fatigue accumulated in the experiment is mostly related to the binocular vision stress of 3D display. The peak velocity‐magnitude relationship of saccadic eye movements decreases after the experiment, and no significant differences are observed in the other saccadic parameters. Our conclusion is that saccadic eye movement, particularly the peak velocity‐magnitude relationship, is a sensitive indicator for visual fatigue caused by 3D display and has the potential to help the establishment of a valid on‐line measure for the detection of 3D visual fatigue.

Evaluation of 3D cognitive fatigue using heart–brain synchronization

The purpose of this study was to identify an evaluation method for 3D cognitive fatigue based on a heart–brain synchronization phenomenon known as the heartbeat evoked potential (HEP). Thirty undergraduate students (15 females) watched a video in both 2D and 3D for an hour. Because visual fatigue is related to cognitive load, the HEP was used as an indicator of communication between the heart and the brain and therefore of cognitive function; responses were compared after 2D and 3D viewing. At the standard EEG sites F3 and F4, the alpha activity of the first and second HEP components was significantly increased after 3D video viewing relative to 2D. This increase likely indicates that sensory input from 3D video requires heavy computation by the brain, stimulating heart activity. The conclusion is that the first and second HEP components are significant parameters that can quantitatively evaluate 3D visual fatigue. Further work is needed to uncover the cause of 3D visual fatigue.

패럴랙스 배리어를 사용한 무안경식 휴대용 3차원 디스플레이의 수평위치에 따른 크로스톡 및 3차원 시각 피로의 측정과 모형 구축

The 3D technology has been spread slowly and the reason would be attributed to the fact that most commercialized 3D displays require 3D glasses. There have been various researches on human factors of glass type 3D display. In this study we measured and modeled crosstalk as well as 3D visual fatigue induced by mobile glassless 3D display. Crosstalk as well as visual fatigue varied depending on horizontal position of the 3D mobile display. Measured crosstalk was relative low around the center of the display and it increased at the side of the display. Similar results were found in the measurement of 3D visual fatigue and discomfort. These results imply that human factors should be considered in the process of design and evaluation of mobile 3D displays. Keyword : Mobile 3D display, glassless, crosstalk, horizontal position 정규논문 (Regular Paper) 방송공학회논문지 제19권 제2호, 2014년 3월 (JBE Vol. 19, No. 2, March 2014) http://dx.doi.org/10.5909/JBE.2014.19.2.215 ISSN 2287-9137 (Online) ISSN 1226-7953 (Print) 216 방송공학회논문지 제19권 제2호, 2014년 3월 (JBE Vol. 19, No. 2, March 2014)

Does visual fatigue from 3D displays affect autonomic regulation and heart rhythm?

Most investigations into the negative effects of viewing stereoscopic 3D content on human health have addressed 3D visual fatigue and visually induced motion sickness (VIMS). Very few, however, have looked into changes in autonomic balance and heart rhythm, which are homeostatic factors that ought to be taken into consideration when assessing the overall impact of 3D video viewing on human health. In this study, 30 participants were randomly assigned to two groups: one group watching a 2D video, (2D-group) and the other watching a 3D video (3D-group). The subjects in the 3D-group showed significantly increased heart rates (HR), indicating arousal, and an increased VLF/HF (Very Low Frequency/High Frequency) ratio (a measure of autonomic balance), compared to those in the 2D-group, indicating that autonomic balance was not stable in the 3D-group. Additionally, a more disordered heart rhythm pattern and increasing heart rate (as determined by the R-peak to R-peak (RR) interval) was observed among subjects in the 3D-group compared to subjects in the 2D-group, further indicating that 3D viewing induces lasting activation of the sympathetic nervous system and interrupts autonomic balance.

Performance Comparison of a SSVEP BCI Task by Individual Stereoscopic 3D Susceptibility

This study aimed at investigating the differences in brain–computer interface (BCI) task performance between 2D and 3D displays depending on their individual susceptibility to stereoscopic 3D. Eleven female and 10 male participants attempted a steady-state visually evoked potential BCI navigation task in a virtual home environment with and without 3D views. Participants were categorized into fatigued and unfatigued groups, depending on their individual susceptibility to 3D, which was characterized using a subjective evaluation method for 3D visual fatigue. The task completion time for the fatigued group under the 3D conditions was significantly delayed relative to the 2D mode. In contrast, a significantly decreased completion time was observed in the 3D view relative to the 2D view for the unfatigued group. The averaged positive predictive value significantly increased in the 3D mode relative to the 2D one for the unfatigued group only. These results are expected to provide a practical implication for enhancing BCI task performance in light of individual vulnerability to 3D.