[in Japanese]

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The surface of a hard disk is extremely flat so that a large amount of data can be stored at high density. This high degree of flatness, however, tends to cause sticking between the disk and the head when the disk starts and stops moving, and this reduces the reliability of the hard disk device. To solve this problem, we have developed an ultrasonic vibration spindle that vibrates the disk when it is turned on and off. We used this spindle in an ultrasonic levitation experiment, and found that by vibrating the spindle in a ring-shape vibration mode. We could keep the head and the disk apart and drastically reduce the friction coefficient between them. Further, by placing a reflection plate in the space above the hard disk at an appropriate plate-disk distance, we could increase the acoustic power. This means that the spindle can be made much smaller.

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We have evaluated the reproduction characteristics of a magnetoresistive (MR) head for a rotary drum in a helical-scan tape system. This MR head was developed for use in a high-capacity tape storage system that has a high data transfer rate and uses a small cassette. Various experimental thin-magnetic-layer metal evaporated (ME) tapes suitable for the MR head, whose magnetic layer thickness is 0.1 μm or less, have been made, and our evaluation was done using such tapes. We found the output voltage of the MR head was 20 times that of an inductive head, and an areal recording density of 1.2 Gbit/ inch² was feasible with the combination of the MR head and the thin-magnetic-layer ME tapes. Moreover, the pulse width and CN ratio showed that the optimum value of Brδ, the product of remanent flux density and magnetic layer thickness of the tape, for the trial MR head was from 140 to 220 G·μm.

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Hard disk drives were developed as a recording medium for computer data, and are now also used to store multimedia data such as video and audio. However, this is not yet a practical medium for use in broadcasting. We are developing a video hard-disk system that will allow high-bitrate recording/playback while maintaining video signal continuity. As a step toward realizing a video hard-disk system, we have developed a hard-disk tool capable of precisely evaluating hard disk performance. It is also essential to model hard disks to efficiently develop a video hard-disk system. In this paper, we describe a method of modeling hard disks, and show how this model can be used to improve the performance of hard disk systems.

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We have developed a character coding watermarking technique based on computer generated holograms (CGHs).Phase information is converted into intensity information where sampling dots of intensity on a CGH surface are expressed by a character pattern.We have demonstrated the effectiveness of this technique through a simulated recovery of CGH data by using the character pattern.Further more, we propose a quadrant distribution of character pattern against cropping attack.It shows that the sampling dots are increased by 100 percent against the same cropping attack.As well, the resolution of the reconstructed image is improved.

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The Digital Micro-mirror Device (DMDTM) and the Digital Light Processing (DLPTM) system utilizing the DMD are used in various types of image projectors, and are now being applied to high-definition television (HDTV) projection systems. Terrestrial HD digital broadcasting service began in the USA in 1998, and satellite HD digital broadcasting is scheduled to start in Japan in DEC 2000. The 720 P-DMD (horizontal pixel number : 1280, vertical pixel number : 720, mirror pitch : 13.8 pm) was developed for consumer HD projector applications to display full extent of broadcast High Definition television. In 1999, a prototype 720 P-DLP rear-projection system was made with the 720 P-DMD. This paper describes the 720 P-DLP system and its digital signal processing technique.

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We are developing a see-through display that uses holographic optical elements (HOEs) for the purpose of realizing a see-through head mounted display (HMD). Our display uses the Maxwellian view, which eliminates the need for focusing with a crystalline lens (ocular accommodation) because its depth field is extremely deep. We previously estimated the optical efficiency of a HOE that has both Maxwellian optics and a see-through function by using still images. In this report, we describe a prototype of a see-through display that provides electrical dynamic images by using a digital micro mirror device (DMD) as an electrical spatial light modulator.

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[in Japanese]

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