The Experts below are selected from a list of 3573 Experts worldwide ranked by ideXlab platform
Laure Leroy - One of the best experts on this subject based on the ideXlab platform.
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ISMAR - Investigating Cyclical Stereoscopy Effects Over Visual Discomfort and Fatigue in Virtual Reality While Learning
2019 IEEE International Symposium on Mixed and Augmented Reality (ISMAR), 2019Co-Authors: Alexis D. Souchet, Stéphanie Philippe, Floriane Ober, Aurelien Leveque, Laure LeroyAbstract:Purpose: It is hypothesized that cyclical Stereoscopy (displaying Stereoscopy or 2D cyclically) has effect over visual fatigue, learning curves and quality of experience, and that those effects are different from regular Stereoscopy. Materials and Methods: 59 participants played a serious game simulating a job interview with a Samsung Gear VR Head Mounted Display (HMD). Participants were randomly assigned to 3 groups: HMD with regular Stereoscopy (S3D) and HMD with cyclical Stereoscopy (cycles of 1 or 3 minutes). Participants played the game thrice (third try on a PC one month later). Visual discomfort, Flow, Presence, were measured with questionnaires. Visual Fatigue was assessed pre-and post-exposure with optometric measures. Learning traces were obtained in-game. Results: Visual discomfort and flow are lower with cyclical-S3D than S3D but not Presence. Cyclical Stereoscopy every 1 minute is more tiring than Stereoscopy. Cyclical Stereoscopy every 3 minutes tends to be more tiring than Stereoscopy. Cyclical Stereoscopy groups improved during Short-Term Learning. None of the statistical tests showed a difference between groups in either Short-Term Learning or Long-Term Learning curves. Conclusion: cyclical Stereoscopy displayed cyclically had a positive impact on Visual Comfort and Flow, but not Presence. It affects oculomotor functions in a HMD while learning with a serious game with low disparities and easy visual tasks. Other visual tasks should be tested, and eye-tracking should be considered to assess visual fatigue during exposure. Results in ecological conditions seem to support models suggesting that activating cyclically stereopsis in a HMD is more tiring than maintaining it.
Yumei Hai - One of the best experts on this subject based on the ideXlab platform.
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Stereoscopy based 3d face recognition system
International Conference on Conceptual Structures, 2010Co-Authors: Emanuele Zappa, Paolo Mazzoleni, Yumei HaiAbstract:Abstract This paper presents an innovative facial recognition algorithm: a stereoscopic calibrated system acquires two images of a subject that are then separately analyzed by an active appearance model code which extracts from each of them 58 homologous points. The triangulation of these points allows the construction of a three-dimensional mask of the face of the individual. This mask is then compared against a database of reference masks. The obtained results are encouraging: preliminary tests on a limited database showed a false rejection rate identically equal to zero and a false acceptance rate of about 3%.
Shengbo Sang - One of the best experts on this subject based on the ideXlab platform.
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Probabilistic assessment of visual fatigue caused by Stereoscopy using dynamic Bayesian networks
Acta ophthalmologica, 2018Co-Authors: Yuan Zhongyun, Zhuo Kai, Qiang Zhang, Chun Zhao, Shengbo SangAbstract:PURPOSE 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. METHODS 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. RESULTS 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. CONCLUSION (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.
Jose Miguel Aguilera - One of the best experts on this subject based on the ideXlab platform.
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computer vision and Stereoscopy for estimating firmness in the salmon salmon salar fillets
Food and Bioprocess Technology, 2010Co-Authors: R Quevedo, Jose Miguel AguileraAbstract:The computer vision and a Stereoscopy technique were used to characterize and detect changes in the capacity of the salmon fillet surface to recover its original form after a constant weight was applied. A curvature index (associated to fillet firmness) calculated by means of 3D information data obtained with the Stereoscopy technique from the fat stripe on the fillets was estimated over 6 months and was suggested as a characteristic of the recovery property of the fresh salmon fillet surface. Simultaneously, instrumental firmness using a LFRA1500 texture was measured. The values for the fresh salmon fillet measurement curvature index during a period of 6 months were established in the range of 0.05 and 0.10 (dimensionless), and this value was used in the experiments to represent fresh salmon fillets. Changes in the curvature index (associated with similar changes in firmness) for salmon fillet surface treated with enzymes (pepsin and papain) were registered on the second day during storage at 2 °C. In general, Stereoscopy is a technique that can be used on salmon fillets to detect changes in the recovery properties of the salmon fillet surface and to determine when salmon fillets can be classified as a fillet that has not been processed with enzymes.
Bernd Inhester - One of the best experts on this subject based on the ideXlab platform.
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Nonlinear Force-free Coronal Magnetic Stereoscopy
The Astrophysical Journal, 2017Co-Authors: Iulia Chifu, Thomas Wiegelmann, Bernd InhesterAbstract:Insights into the 3D structure of the solar coronal magnetic field have been obtained in the past by two completely different approaches. The first approach are nonlinear force-free field (NLFFF) extrapolations, which use photospheric vector magnetograms as boundary condition. The second approach uses Stereoscopy of coronal magnetic loops observed in EUV coronal images from different vantage points. Both approaches have their strengths and weaknesses. Extrapolation methods are sensitive to noise and inconsistencies in the boundary data, and the accuracy of Stereoscopy is affected by the ability of identifying the same structure in different images and by the separation angle between the view directions. As a consequence, for the same observational data, the 3D coronal magnetic fields computed with the two methods do not necessarily coincide. In an earlier work (Paper I) we extended our NLFFF optimization code by including stereoscopic constrains. The method was successfully tested with synthetic data, and within this work, we apply the newly developed code to a combined data set from SDO/HMI, SDO/AIA, and the two STEREO spacecraft. The extended method (called S-NLFFF) contains an additional term that monitors and minimizes the angle between the local magnetic field direction and the orientation of the 3D coronal loops reconstructed by Stereoscopy. We find that when we prescribe the shape of the 3D stereoscopically reconstructed loops, the S-NLFFF method leads to a much better agreement between the modeled field and the stereoscopically reconstructed loops. We also find an appreciable decrease by a factor of two in the angle between the current and the magnetic field. This indicates the improved quality of the force-free solution obtained by S-NLFFF.
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Magnetic Stereoscopy of Coronal Loops in NOAA 8891
Solar Physics, 2007Co-Authors: Li Feng, Bernd Inhester, Thomas Wiegelmann, Sami K. Solanki, Weiqun Gan, P. RuanAbstract:The Solar TErrestrial RElations Observatory (STEREO) requires powerful tools for the three-dimensional (3D) reconstruction of the solar corona. Here we test such a program with data from SOHO and TRACE. By taking advantage of solar rotation, a newly developed Stereoscopy tool for the reconstruction of coronal loops is applied to the solar active region NOAA 8891 observed from 1 March to 2 March 2000. The stereoscopic reconstruction is composed of three steps. First, we identify loop structures in two TRACE images observed from two vantage viewpoints approximately 17 degrees apart, which corresponds to observations made about 30 hours apart. In the second step, we extrapolate the magnetic field in the corona with the linear force-free field model from the photospheric line-of-sight SOHO/MDI data. Finally, combining the extrapolated field lines and one-dimensional loop curves from two different viewpoints, we obtain the 3D loop structures with the magnetic Stereoscopy tool. We demonstrate that by including the magnetic modeling this tool is more powerful than pure geometrical Stereoscopy, especially in resolving the ambiguities generated by classical Stereoscopy. This work will be applied to the STEREO mission in the near future.
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Stereoscopy basics for the STEREO mission
arXiv: Astrophysics, 2006Co-Authors: Bernd InhesterAbstract:We discuss some basic principles of Stereoscopy and their relevance to the reconstruction of coronal loops. The aim of the paper is to make the solar physicist familiar with basic Stereoscopy principles and to give hints how they may apply to the analysis of data from the forthcoming STEREO mission. We disucss the geometry of the solar coronal stereo problem, give the basic principles of a tie-point reconstruction algorithm and consider ambiguities and resolution errors. Finally we mention extensions to plain Stereoscopy such as a third view, a tomography-like approach and how magnetic field information can be used to improve the reconstruction.
