860 research outputs found

    Visual experience of 3D TV

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    BiosignalĆł poĆŸymiĆł regos diskomfortui vertinti iĆĄskyrimas ir tyrimas

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    Comfortable stereoscopic perception continues to be an essential area of research. The growing interest in virtual reality content and increasing market for head-mounted displays (HMDs) still cause issues of balancing depth perception and comfortable viewing. Stereoscopic views are stimulating binocular cues – one type of several available human visual depth cues which becomes conflicting cues when stereoscopic displays are used. Depth perception by binocular cues is based on matching of image features from one retina with corresponding features from the second retina. It is known that our eyes can tolerate small amounts of retinal defocus, which is also known as Depth of Focus. When magnitudes are larger, a problem of visual discomfort arises. The research object of the doctoral dissertation is a visual discomfort level. This work aimed at the objective evaluation of visual discomfort, based on physiological signals. Different levels of disparity and the number of details in stereoscopic views in some cases make it difficult to find the focus point for comfortable depth perception quickly. During this investigation, a tendency for differences in single sensor-based electroencephalographic EEG signal activity at specific frequencies was found. Additionally, changes in eye tracker collected gaze signals were also found. A dataset of EEG and gaze signal records from 28 control subjects was collected and used for further evaluation. The dissertation consists of an introduction, three chapters and general conclusions. The first chapter reveals the fundamental knowledge ways of measuring visual discomfort based on objective and subjective methods. In the second chapter theoretical research results are presented. This research was aimed to investigate methods which use physiological signals to detect changes on the level of sense of presence. Results of the experimental research are presented in the third chapter. This research aimed to find differences in collected physiological signals when a level of visual discomfort changes. An experiment with 28 control subjects was conducted to collect these signals. The results of the thesis were published in six scientific publications – three in peer-reviewed scientific papers, three in conference proceedings. Additionally, the results of the research were presented in 8 conferences.Dissertatio

    Visual discomfort whilst viewing 3D stereoscopic stimuli

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    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)

    Aerospace medicine and biology: A continuing bibliography with indexes (supplement 341)

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    This bibliography lists 133 reports, articles and other documents introduced into the NASA Scientific and Technical Information System during September 1990. Subject coverage includes: aerospace medicine and psychology, life support systems and controlled environments, safety equipment, exobiology and extraterrestrial life, and flight crew behavior and performance

    Une méthode pour l'évaluation de la qualité des images 3D stéréoscopiques.

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    Dans le contexte d'un intĂ©rĂȘt grandissant pour les systĂšmes stĂ©rĂ©oscopiques, mais sans mĂ©thodes reproductible pour estimer leur qualitĂ©, notre travail propose une contribution Ă  la meilleure comprĂ©hension des mĂ©canismes de perception et de jugement humains relatifs au concept multi-dimensionnel de qualitĂ© d'image stĂ©rĂ©oscopique. Dans cette optique, notre dĂ©marche s'est basĂ©e sur un certain nombre d'outils : nous avons proposĂ© un cadre adaptĂ© afin de structurer le processus d'analyse de la qualitĂ© des images stĂ©rĂ©oscopiques, nous avons implĂ©mentĂ© dans notre laboratoire un systĂšme expĂ©rimental afin de conduire plusieurs tests, nous avons crĂ©e trois bases de donnĂ©es d'images stĂ©rĂ©oscopiques contenant des configurations prĂ©cises et enfin nous avons conduit plusieurs expĂ©riences basĂ©es sur ces collections d'images. La grande quantitĂ© d'information obtenue par l'intermĂ©diaire de ces expĂ©rimentations a Ă©tĂ© utilisĂ©e afin de construire un premier modĂšle mathĂ©matique permettant d'expliquer la perception globale de la qualitĂ© de la stĂ©rĂ©oscopie en fonction des paramĂštres physiques des images Ă©tudiĂ©e.In a context of ever-growing interest in stereoscopic systems, but where no standardized algorithmic methods of stereoscopic quality assessment exist, our work stands as a step forward in the understanding of the human perception and judgment mechanisms related to the multidimensional concept of stereoscopic image quality. We used a series of tools in order to perform in-depth investigations in this direction: we proposed an adapted framework to structure the process of stereoscopic quality assessment, we implemented a stereoscopic system in our laboratory for performing various tests, we created three stereoscopic datasets with precise structures, and we performed several experimental studies using these datasets. The numerous experimental data obtained were used in order to propose a first mathematical framework for explaining the overall percept of stereoscopic quality in function of the physical parameters of the stereoscopic images under study.SAVOIE-SCD - Bib.Ă©lectronique (730659901) / SudocGRENOBLE1/INP-Bib.Ă©lectronique (384210012) / SudocGRENOBLE2/3-Bib.Ă©lectronique (384219901) / SudocSudocFranceF

    Photoelastic Stress Analysis

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    Remote Visual Observation of Real Places Through Virtual Reality Headsets

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    Virtual Reality has always represented a fascinating yet powerful opportunity that has attracted studies and technology developments, especially since the latest release on the market of powerful high-resolution and wide field-of-view VR headsets. While the great potential of such VR systems is common and accepted knowledge, issues remain related to how to design systems and setups capable of fully exploiting the latest hardware advances. The aim of the proposed research is to study and understand how to increase the perceived level of realism and sense of presence when remotely observing real places through VR headset displays. Hence, to produce a set of guidelines that give directions to system designers about how to optimize the display-camera setup to enhance performance, focusing on remote visual observation of real places. The outcome of this investigation represents unique knowledge that is believed to be very beneficial for better VR headset designs towards improved remote observation systems. To achieve the proposed goal, this thesis presents a thorough investigation of existing literature and previous researches, which is carried out systematically to identify the most important factors ruling realism, depth perception, comfort, and sense of presence in VR headset observation. Once identified, these factors are further discussed and assessed through a series of experiments and usability studies, based on a predefined set of research questions. More specifically, the role of familiarity with the observed place, the role of the environment characteristics shown to the viewer, and the role of the display used for the remote observation of the virtual environment are further investigated. To gain more insights, two usability studies are proposed with the aim of defining guidelines and best practices. The main outcomes from the two studies demonstrate that test users can experience an enhanced realistic observation when natural features, higher resolution displays, natural illumination, and high image contrast are used in Mobile VR. In terms of comfort, simple scene layouts and relaxing environments are considered ideal to reduce visual fatigue and eye strain. Furthermore, sense of presence increases when observed environments induce strong emotions, and depth perception improves in VR when several monocular cues such as lights and shadows are combined with binocular depth cues. Based on these results, this investigation then presents a focused evaluation on the outcomes and introduces an innovative eye-adapted High Dynamic Range (HDR) approach, which the author believes to be of great improvement in the context of remote observation when combined with eye-tracked VR headsets. Within this purpose, a third user study is proposed to compare static HDR and eye-adapted HDR observation in VR, to assess that the latter can improve realism, depth perception, sense of presence, and in certain cases even comfort. Results from this last study confirmed the author expectations, proving that eye-adapted HDR and eye tracking should be used to achieve best visual performances for remote observation in modern VR systems

    A head-mounted display as a personal viewing device : Dimensions of subjective experiences

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    The use of head-mounted displays (HMDs) can produce both positive and negative experiences. In an effort increase positive experiences and avoid negative ones, researchers have identified a number of variables that may cause sickness and eyestrain, although the exact nature of the relationship to HMDs may vary, depending on the tasks and the environments. Other non-sickness-related aspects of HMDs, such as users opinions and future decisions associated with task enjoyment and interest, have attracted little attention in the research community. In this thesis, user experiences associated with the use of monocular and bi-ocular HMDs were studied. These include eyestrain and sickness caused by current HMDs, the advantages and disadvantages of adjustable HMDs, HMDs as accessories for small multimedia devices, and the impact of individual characteristics and evaluated experiences on reported outcomes and opinions. The results indicate that today s commercial HMDs do not induce serious sickness or eyestrain. Reported adverse symptoms have some influence on HMD-related opinions, but the nature of the impact depends on the tasks and the devices used. As an accessory to handheld devices and as a personal viewing device, HMDs may increase use duration and enable users to perform tasks not suitable for small screens. Well-designed and functional, adjustable HMDs, especially monocular HMDs, increase viewing comfort and usability, which in turn may have a positive effect on product-related satisfaction. The role of individual characteristics in understanding HMD-related experiences has not changed significantly. Explaining other HMD-related experiences, especially forward-looking interests, also requires understanding more stable individual traits and motivations.PÀÀssÀ pidettÀvÀn nÀytön kÀyttö voi olla mukava kokemus ilman silmÀrasituksen tai pahoinvoinnin oireita. Joskus siihen voi liittyÀ myös erilaisia negatiivisia tuntemuksia. Vuosien varrella on tunnistettu monia systeemiin, kÀyttÀjÀÀn ja tehtÀvÀÀn liittyviÀ taustamuuttujia, joilla on vaikutusta negatiivisten tuntemusten ja kokemusten syntyyn. Muita, pÀÀssÀ pidettÀvÀn nÀytön kÀyttöön liittyviÀ kokemuksia ja kÀyttÀjien mielipiteitÀ on tutkittu vain vÀhÀn tai ei ollenkaan. TÀssÀ vÀitöskirjassa tutkittiin markkinoilla olevien erilaisten pÀÀssÀ pidettÀvien nÀyttöjen kÀyttökokemuksia. Yksityiskohtaisemmin tarkasteltiin pÀÀssÀ pidettÀvien nÀyttöjen kÀyttöön liittyvÀ silmÀrasitusta ja pahoinvointia sekÀ nÀytön sÀÀtömahdollisuuden hyötyjÀ ja haittoja kÀyttÀjÀn nÀkökulmasta. LisÀksi tutkittiin laitteen kÀyttöÀ lisÀlaitteena muille pienille multimedialaitteille sekÀ sitÀ, miten erilaiset taustamuuttujat ja laitteen kÀyttöön liittyvÀt kokemukset auttavat meitÀ ymmÀrtÀmÀÀn laitteen tulevaan kÀyttöön liittyviÀ mielipiteitÀ. TÀssÀ vÀitöskirjassa esitettyjen tutkimustulosten mukaan pÀÀssÀ pidettÀvÀt nÀytöt voivat aiheuttaa lievÀÀ silmÀrasitusta ja pahoinvointia, mutta erot muihin nÀyttöihin ovat selvÀsti pienentyneet. PÀÀssÀ pidettÀvÀn nÀytön sÀÀtömahdollisuus parantaa katselukokemusta etenkin monokulaarisen pÀÀssÀ pidettÀvÀn nÀytön tapauksessa, mutta nÀyttöjen sÀÀdettÀvyys voi hyödyttÀÀ myös bi-okulaaristen nÀyttöjen kÀyttÀjiÀ. PÀÀssÀ pidettÀvÀn nÀytön kÀyttö lisÀlaitteena pienille multimedialaitteille pidentÀÀ sovelluksen kÀyttöaikaa ja mahdollistaa sellaisten tehtÀvien suorituksen, jotka olisivat erittÀin vaativia pienellÀ nÀytöllÀ. Aikaisemmin julkaistujen tulosten mukaan monet kÀyttÀjÀn yksilölliset ominaisuudet auttavat ymmÀrtÀmÀÀn koettua silmÀrasitusta ja pahoinvointia. Myös vÀitöskirjassa esitetyt tulokset tukevat tÀtÀ nÀkemystÀ. JohtopÀÀtöksenÀ voidaankin esittÀÀ, ettÀ jos tavoitteena on ymmÀrtÀÀ laitteen tulevaan kÀyttöön liittyviÀ mielipiteitÀ, niin vÀlittömien kÀyttökokemusten lisÀksi pitÀisi tarkastella myös kÀyttÀjÀn persoonallisuuspiirteiden ja motivaatioiden vaikutusta

    Perceptual Quality-of-Experience of Stereoscopic 3D Images and Videos

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    With the fast development of 3D acquisition, communication, processing and display technologies, automatic quality assessment of 3D images and videos has become ever important. Nevertheless, recent progress on 3D image quality assessment (IQA) and video quality assessment (VQA) remains limited. The purpose of this research is to investigate various aspects of human visual quality-of-experience (QoE) when viewing stereoscopic 3D images/videos and to develop objective quality assessment models that automatically predict visual QoE of 3D images/videos. Firstly, we create a new subjective 3D-IQA database that has two features that are lacking in the literature, i.e., the inclusion of both 2D and 3D images, and the inclusion of mixed distortion types. We observe strong distortion type dependent bias when using the direct average of 2D image quality to predict 3D image quality. We propose a binocular rivalry inspired multi-scale model to predict the quality of stereoscopic images and the results show that the proposed model eliminates the prediction bias, leading to significantly improved quality predictions. Second, we carry out two subjective studies on depth perception of stereoscopic 3D images. The first one follows a traditional framework where subjects are asked to rate depth quality directly on distorted stereopairs. The second one uses a novel approach, where the stimuli are synthesized independent of the background image content and the subjects are asked to identify depth changes and label the polarities of depth. Our analysis shows that the second approach is much more effective at singling out the contributions of stereo cues in depth perception. We initialize the notion of depth perception difficulty index (DPDI) and propose a novel computational model for DPDI prediction. The results show that the proposed model leads to highly promising DPDI prediction performance. Thirdly, we carry out subjective 3D-VQA experiments on two databases that contain various asymmetrically compressed stereoscopic 3D videos. We then compare different mixed-distortions asymmetric stereoscopic video coding schemes with symmetric coding methods and verify their potential coding gains. We propose a model to account for the prediction bias from using direct averaging of 2D video quality to predict 3D video quality. The results show that the proposed model leads to significantly improved quality predictions and can help us predict the coding gain of mixed-distortions asymmetric video compression. Fourthly, we investigate the problem of objective quality assessment of Multi-view-plus-depth (MVD) images, with a main focus on the pre- depth-image-based-rendering (pre-DIBR) case. We find that existing IQA methods are difficult to be employed as a guiding criterion in the optimization of MVD video coding and transmission systems when applied post-DIBR. We propose a novel pre-DIBR method based on information content weighting of both texture and depth images, which demonstrates competitive performance against state-of-the-art IQA models applied post-DIBR
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