[in Japanese]

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When a transparent surface overlays another surface, we can perceive both surfaces simultaneously in the overlapping region. For chromatic transparency, the overlapping region has a single chromaticity, but perceptually it is split into two differently colored layers. In this study, we found that the perception of a surface could change the chromatic appearance of the overlapping region. We used a stimulus surface filled with random dots. The display was divided diagonally into two different colored regions. A square region was presented in the center. Two squares appeared by motion of random dots in each surround. These were arranged so that the center square became the overlapping region. We measured the percentage of perceiving the center square to be transparent as a function of the speed in the center square. Transparency occurred when all the square regions moved at the same speed. We found that the center square dramatically changed in appearance from opaque to transparent depending on its speed.

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We propose a motion perception model taking into consideration the results of a physiological study that there are different latencies of response to random dot kinematograms (RDKs) motion stimuli and line pattern motion stimuli in middle temporal area (MT). The model is composed of spatiotemporal filters and a competition process. The response latency of MT in this model is longer in response to RDKs than to line patterns. This response behavior has good correspondence with the physiological study. We show that the response of this model is not only dynamic but also robust against noisy motion stimuli.

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An approach to designing visual displays for the elderly is described that is based on a model of human vision. This model is represented by two properties : contrast sensitivity and ocular transmittance. Real-time video-processing hardware is used to compensate for the deterioration in human vision that comes with aging. It sharpens edges and corrects the color balance. Psychophysical experiments using test charts showed that the proposed approach improves the contrast sensitivity of elderly viewers. A prototype system improved more than two times of the visibility of images shown on visual displays.

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When a scene is represented in a binocular stereoscopic display, depth distortions are perceived at the edges of the images in front of the screen. In our previous research (Ishigure et al., ITE, 1996), we showed that adding a virtual frame with a crossed disparity relative to the objects in stereoscopic images can eliminate the distortion. In the present study, we investigated how the depth distortion affects vergence eye movements and whether a virtual frame plays a role. The experimental results show : (1) when subjects perceive a depth distortion, the eyes converge to a point closer to the disparity of the screen than that of the object, (2) when the shape of the distorted object changes, convergence also changes, and (3) when the virtual frame has a crossed disparity, the point of convergence is located at the position indicated by the disparity of the object. The results indicate that presenting a stereoscopic image with an accompanying virtual frame prevents an undesired shift in convergence.

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We investigated the effect of visual information on an observer's body control. We measured observers' body sway and perceived magnitude of motion in depth while observing a stimulus with changing disparity and/or changing size. The stimulus variable was the size of the moving area. For the stimuli with changing disparity, local peaks in the power spectrum for the body sway data were clearly observed at the frequencies of the image motion when the size of the moving area was large. For the stimuli with changing size, no local peaks were not found. Psychophysical results showed that the magnitude of perceived depth for the stimulus with changing disparity decreased as the size of the moving area increased. However, changing size produced a strong sensation of motion in depth for the stimuli irrespective of the size of the moving area. These results indicate that changing disparity in a large field contributes to body posture control and supports the idea that visual perception and motor control are mediated by different pathways.

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In order to construct virtual environments, most systems have used 3 D displays utilizing retinal disparity. However, the depth perception of virtual objects with such displays is known to differ from that of real objects, which degrades task performance. In this study, we developed a hand-held device employing tactile phantom sensation providing depth cues in addition to a visual 3 D display, in order to handle virtual objects. The distance in the depth direction between a virtual object and the device was mapped to the position of the phantom sensation. Operator task performance with this device moving and deforming wire-framed virtual objects was measured under four display modes providing various depth cues. It was shown that the effectiveness of the device was related to the depth cues in the 3 D visual display methods and that the device was effective at reducing the time taken to deform virtual objects.

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We are studying an intelligent robot camera system that can automatically shoot images with a powerful sense of reality. To clarify the relationship between the size of a subject, shooting velocity, and position of the subject in the image, a basic experiment was conducted on the shooting of a moving subject. The following points were clarified. The subject's position in the image seems to be more closely related to the size of the subject than its velocity ; the larger the subject and the faster it is moving, the greater the values for the distribution of the subject's position. We also found that if a subject moves outside the best position in the image, its position is not corrected immediately but the shooting continues keeping the maximum velocity of positional change within about 0.20 to 0.35. We also conducted subjective image evaluation experiments using a camera control system. This has revealed that the factors in subjective evaluation of camera work may be divided into four groups representing continuation, vividness, sensitivity, and human-warmth, and that the tested subjects were liable to feel shots, taken with techniques similar to those used by cameramen were more human-like, so they gave them relatively high evaluations.

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[in Japanese]

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With its rapid increase in popularity, the Internet has become a new form of mass media covering the whole world. Compared with the other mass media such as TV, radio, and newspapers, the Internet has the advantage of being interactive. However, the current Internet has several limitations. Its network bandwidth is still too narrow to carry a full-motion video stream and because it is based on the client/server model, its servers require powerful processors to support the huge number of customers scattered over the Internet. As a result, we have to take care designing and implementing network services for the Internet. In this paper, we describe our experience in making a multimedia information feeding system for large-scale social events. A case study on the system for high-school baseball games in Koshien stadium is explained.

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We investigated the influence of age-related changes in vision on optimum display luminance, contrast, and character size of transmissive liquid crystal displays (LCDs). Young (28 persons with a mean age of 21.7 years) and old (28 persons, mean age of 68.1 years) subjects rated the subjective legibility and preference of 25 luminance and contrast combinations for five character sizes which were displayed on a TFT-LCD. The preferred angular character size for a display luminance of 80 cd/m² was 33 minutes for old subjects and 32 minutes for young subjects. Display luminance requirements for subjective legibility in old subjects were twice as high as for young subjects. However, the actual display luminance preferred by old subjects was 130% of that by young subjects. These results indicate that old subjects must select a higher display luminance to maintain legibility. This may be due to an age-related reduction in visual contrast sensitivity in lower luminance conditions.

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