In recent years, as vehicle technology has advanced, the use of on-board display devices has increased. In particular, vehicles with navigation systems are rapidly increasing in use. With such systems, when a driver operates a vehicle, the driver detects and judges road situations while looking at the route-guided map on the navigation system display. Thus, from the safety point of view, improvement of visibility of the navigation system is very important. We have developed a noncontact gaze duration measurement system for on-board navigation systems. The system uses a TV camera on the dashboard to detect the driver's eye movements that are illuminated by infrared rays. In addition, the usefulness of the navigation system with voice route guidance compared with a conventional nonvoice system is demonstrated using measurements based on this method in the daytime and at night time. It is clear that the voice guidance is effective in decreasing gaze duration.

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This paper describes an analytical method to evaluate the legibility of displayed characters through detectability of pictorial patterns. In image pickup devices including eyes, shot noise is produced during the process of photoelectric conversion, and result in limited detection of intended pictures. Hence it can be considered that detectability of pictorial pattern is an important element for evaluation of the image quality. From this view point, an analysis is conducted on relationship between the resolution of display and the detectability of displayed Kanji patterns. This analysis is performed on the basis of lijima's picture observation theory. The detectability of each displayed pattern is compared with the result of subjective evaluation of legibility. Consequently, it is shown that the deterioration of legibility of characters which resulted from the resolution of display confirms the change in detectability. By this means, validity evaluation conducted on the legibility of displayed characters through detectability is verified

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Margins of disk-tilt and lens-tilt for a phase-change optical head were examined digital recording at a bit length of half of a laser wavelength. The margins for an objective lens of numerical aperture 0.6 for 0.6 mm in disk-thickness were more than three times that of the lens with a 1.2mm disk-thickness according to characteristics of bit-error-rate using partial response maximum likelihood of three-level Viterbi decoding.

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This study examines a contribution of the visual system to the acquisition of visual information during saccadic eye movements (saccade). In the experiment, when the observer made a saccade, the location of a Kanji character displayed on a CRT screen was transferred a random distance and direction, or was kept at the original position. When the character was transferred to a new position, the recognition rate of the character decreased proportionally to the increase in distance between the fixation point after the saccade and the center of the character, in comparison with the case when the character was kept at the original position. We attempted to control the spatial attention during the same tasks. The result suggests that the spatial attention before a saccade might also be involved in the process of visual information acquisition during saccades and the visual system may integrate the positional information into the visual feature information.

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This paper describes a method for estimating the color vectors of a light source and an object surface by means of line detection from a histogram of the color image. The object is supposed to be an inhomogeneous dielectric object such as plastics with a smooth surface. First, we suggest the characteristics of the color histogram in a RGB space. The histogram forms a combination of two straight clusters of highlight pixels by specular reflection, and matte pixels by diffuse reflection. The estimation of two color vectors is then reduced to finding the gradients of straight lines for the two clusters. Next, basic algorithms for extracting a line from a cluster are shown using the principal component analysis and Hough transform. Moreover, an effective algorithm is proposed based on iteratively splitting and merging the histogram on the color signal plane. Finally, the usefulness of the method is shown in an experiment.

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This paper describes an image compression method associating a wavelet packet and a zerotree coding scheme. The wavelet packet, which gives a generalized multiresolution analysis, has been applied so as to reduce the correlation of the image pixels. To encode the adaptive wavelet packet coefficients, we apply the zerotree structure, which can reduce the correlation across the decomposed component images by exploiting the self-similarity among the components. In this case, the decomposition criterion with regard to each decomposition level is computed using a simplified local zerotree structure. If a target bit rate or a target distortion is decided, we can obtain the most suitable decompositions using an operation with fewer computations. Simulation results show that the proposed method has a better coding efficiency than the wavelet octave decomposition case by about 1 dB, and the JPEG baseline case by about 3 dB in PSNR at 0.4 bpp using the standard image “BARBARA”.

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[in Japanese]

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