Toshihiro Sugaya

A 16MB 3.5 inch Ba-Ferrite flexible disk drive with dual track following servo modes

A large capacity high-speed-access 3.5 inch flexible disk drive has been achieved, using a barium ferrite 3.5 inch flexible disk and newly developed sector servo technology. The flexible disk drive has a 16 megabyte unformatted capacity, a 50 millisecond average seek time and a 3 megabit/second data transfer rate. It can use both concentric track disks for conventional computer systems and spiral track disks for high speed data transfer systems, such as hard disk drive (HDD) back-up, image data storing, and so on.

Holographic system for filing and retrieving patents.

A large-capacity high-speed holographic system has been developed for filing and retrieving the patent literature. This machine can store 280,000 pages of the Japanese patents journal (or the U.S. Official Gazette) and any one page can be retrieved within 1 sec. A high-resolution TV camera with 2110 scanning lines and a CRT display terminal with 1055 scanning lines were also developed to clearly represent fine drawings and letters in the patents. The system developed is equipped with a momentary 2.6-Mbyte electric one-frame memory for scanning mode conversion. Any image on the CRT can be printed out on a plain sheet of paper with a laser beam printer.

A servo method for a large-capacity floppy disk drive with downward compatibility

A novel servo method, in which a linear voice coil motor (LVCM) with a simple optical scale is controlled by a mu CPU, has been developed. It has a downward read-compatible mode with 135 tracks/in (TPI) and a large-capacity 16-MByte mode with 542 TPI, and it achieves an average seeking time of 25 ms. The drive is expected to be used in such applications as peripheral memories and hard-disk-drive back-ups. >

Holograms produced with double-heterojunction laser illumination

Abstract Off-axis holograms have been constructed with a double-heterojunction (Ga, Al) As-GaAs semiconductor laser, and image reconstruction has been accomplished using a semiconductor and a He-Ne laser. The reconstructed real images were quite clear, and the signal-to-noise ratio of those images was about 10. Experiments suggest that semiconductor lasers can successfully be applied to coherent optics.

High-density recording for greater than 1-GByte capacity using a 90-mm phase-change optical disk

The mark edge recording characteristics of a new thermally balanced phase-change optical disk operating at a wavelength of 690 nm have been studied, especially from the viewpoint of designing an optical disk drive. As a recording method, the multi-pulse write compensation method with constant duration of the read power level immediately after every multi-pulse, called the off-pulse, was applied. A high carrier-to-noise ratio (CNR) of 54 dB, a high erasability of 35 dB, and an overwrite power margin from -15% to +5% were obtained for a bit length of 0.5 micrometers and a track pitch of 1.0 micrometers at 14.7 m/s linear velocity. These results mean that it is possible to design an optical disk drive providing a capacity of 1.1 GBytes using a 90 mm double-sided disk. Further, it has been found that the off-pulse plays a very important role in controlling the precision of mark edge recording.

High-density overwrite recording for a phase-change medium using a visible-light laser diode

A fast data transfer and high density recording was realized, using a 30 mw visible laser and a GeTeSb phase-change medium. Fast laser power control technique was used for suppressing the laser light power fluctuations, and a RIN of -123 dB was obtained. Using this technique, a CNR of 56 dB and an erase ratio of 25 dB was obtained with a mark pitch of 1.25 micrometers for an overwritable phase change medium.

High-density mark position recording on a 90-mm phase-change optical disk

The attainable recording density of a thermally balanced phase-change optical disk with the mark position recording method have been studied, focusing on the viewpoint of designing an optical disk memory system. A new recording method with constant duration of the read power level after every write-pulse, called the off-pulse, was applied. A wide overwrite power margin from -20% to +10% was obtained for a bit length of 0.63 micrometers and a track pitch of 0.9 micrometers . These results mean that it is possible to attain 1.3 GByte capacity in a 90 mm double-sided disk with the zoned constant angular velocity format.