[in Japanese]

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[in Japanese]

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TWISTER I (Telexistence Wide-angle Immersive STEReoscope, Model I) is an autostereoscopic display that is designed for a face-to-face tele-communication system called “mutual telexistence.” By rotating display units that consist of LED arrays and a barrier around a viewer, TWISTER I can display panoramic stereoscopic images that can be observed without the use of special eyewear. This “glassless” feature is essential for applying this apparatus to mutual telexistence because eye contact is important in non-verbal communication.

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Integral photography (IP) is a technique for creating 3 D images that can be seen from any viewing point without the aid of special viewing glasses. In ordinary 2D imaging systems, if the camera is focused on a specific subject, other subjects which around it are out of focus, lowers the resolution of the picture. For IP, subjects that are widely distributed in the depth direction must be reproduced with high resolution. Detailed studies have not been made on filming. First, the characteristics of resolution by the product of their modulation transfer functions (overall MTF) is evaluated. Next, the relationship between the overall MTF at the Nyquist frequency for IP and how the pickup system is focused on the subject is clarified. It is found that by focusing on the observer or at infinity, constant responses can be gained for the reconstructed images whose original subjects are widely distributed towards depth direction.

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This paper describes enlargement of the viewing zone angle in a hologram sampled by pixels. If the angle between the object beam and the reference beam is larger than the angle determined by the sampling period on the hologram plane, aliasing occurs in the fringe patterns. First, we demonstrate that high order diffraction beams reproduced from fringe patterns containing aliasing components can be equivalent to original object beams. Next, we propose a method by which the angle of the viewing zone can be enlarged by combining these high-order reconstructed beams from the fringe patterns with aliasing. Finally, we confirm the effectiveness of the proposed method in an optical experiment which temporally combined these high-order reconstructed beams.

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Many immersive projection displays like the CAVE (CAVE Automatic Virtual Environment) system have been developed. These systems can realize highly immersive virtual environments, and the utililation of these virtual environments is expected in various fields. However, there are many problems regarding the practical use of immersive virtual environments. Depth perception errors are especially serious for interactive applications in immersive virtual environments. In this paper, we provide a view-dependent focal blur effect in immersive virtual environments and examine its effects on depth perception and sense of reality of virtual environments. The effect is synchronized with viewing direction, and it can generate natural blur effect in one's field of view. We show experimentally that the focal blur effect enables us to perceive depth informations accurately, and enhances the sense of reality of virtual environments.

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Stereoscopic image systems based on binocular parallax can present a stereo pair of images with significant binocular parallax. However, if such parallax often approaches or exceeds the viewer's fusional ability, eye strain or visual fatigue may result. In this regard, it is necessary to assess many human subjects in order to design stereoscopic image systems. We measured fusional vergence limits (or diplopia threshold) of many people without any additional correction of ophthalmic function from the ordinary because of the idea that the variation of the ophthalmic function of many people is one of the factors in the distribution of fusional vergence limits. As a result, the distribution function of fusional vergence limits was clarified. This result will contribute the design of stereoscopic image systems and contents. We also found that the experience of watching stereoscopic contents affects the fusional convergence limits, and that the viewer's eye position (heterophoria) shifts the range of fusional vergence.

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Visual fatigue induced by viewing stereoscopic and planar HDTV images for about one hour at a viewing distance of 4.5m was evaluated. Scenes giving rise to particular visual discomfort were identified by continuous subjective evaluation, and the extent of the induced fatigue was estimated using both this and the difference in accommodation responses before and after viewing the test material. Results suggested that such scenes exercise spatio-temporal frequency limitations of binocular fusion mechanisms, which are more restrictive than comparable limitations for planar moving images. Moreover, even when the accommodation mechanism was judged to be operating open-loop, fatigue was clearly evident in the deterioration of the accommodation response. The results showed that in order to create visually comfortable stereoscopic images, it is necessary to consider not only the much-investigated conflict between vergence eye movement and accommodation, but also visual functions concerned with the processing of parallax.

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A method is described for acquiring textures without highlights or shading for use in an image-based virtual studio for TV program production. In an image-based virtual studio a virtual set is made using video components, i.e. shapes and textures from real objects. If the textures of video components have highlights or shading due to lighting, the composite images are unnatural. The proposed method uses polarized light, rotary polarized filter in front of a camera, and information on light position to remove the highlights and shading from textures, thereby enabling images to be composed under any lighting condition. The effectiveness of the method was demonstrated experimentally.

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In this paper, estimation method of fish position and posture from video using object matching technique is proposed. In the object matching, 3D reference model is divided into three parts, head, body and fins to accelerate the object matching process. NURBS (Non-Uniform Rational B-Spline) is employed for body model in order to represent flexible fish body postures using a small number of control points. The control points of the model is obtained by nine motion parameters, i.e. the center of gravity, the inclination of a fish's head and the angles between skeletons which represent the posture of the body. Some basic behaviors are segmented from the obtained 3D positions and postures by using the characteristics of the motion of fish. Finally, a novel locomotion is generated using the segmented basic behaviors according to the segment connection rule.

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[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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The coding efficiency of block-based video coding methods such as MPEG-2 is low in parts where different regions coexist. Segmentation-based methods, therefore, have great potential as next-generation video coding schemes. The segmentation method described here minimizes the generated entropy and is used for an optimal segmentation-based video coding scheme that is adaptive to coding rates. The method achieves optimal segmentation under a rate constraint by es-timating generated bits according to quantization step size and by the use of layered dynamic programming. This leads to higher efficiency compared with the conventional block-based coding for many kinds of video sequence.

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Modulation transfer function (MTF) quantitatively describes a display' s resolution characteristics. It involves two measurement methods : the impulse method and the sinusoidal method. The authors compared the two methods and showed that the sinusoidal method is the best of the two because the video circuit characteristics are involved in the results. The MTF measurement method for moving images is also investigated.

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This paper describes an investigation results of optimum screen size and viewing distance (angle) for viewing ultra high-definition and wide-screen television (UDW), and the psychological effects of UDW images. First, it is found that a shorter relative viewing distance is preferable to that of the HDTV system and that the preferred viewing distance for UDW images depends not on relative figures using the image height, but instead screen size. Second, it is found that the preferred viewing angles coincide with the positions where the maximum combined effects of “potency” and “comfortableness” are obtained, and that, compared with the HDTV system, UDW images, when viewed at the preferred viewing angles, can give much higher level of emotional feeling with regard to both “potency” and “comfortableness”.

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