Shigekazu Minechika

Erasable digital audio disk system.

Following the popularization of the compact disc, much attention has been paid to development of an erasable optical disk. A magnetooptical disk has proved the most useful in our development of a digital audio disk system which cannot only play and record but also has erase and rewrite disks. This system using MO disks is capable of playing 45-min PCM sound on a CD format which makes high-fidelity sound with a low word error rate of 10−9 (after error correction). This system can also be used for the compact disk playback.

Baseband Hi-Vision Video Disc.

ディスクの両面を同時に, 2個のピックアップで読取る両面同時再生方式を開発し, CLV (Constant Linear Velocity) ディスク1枚で, 連続再生時間30分のべースバンドハイビジョンビデオディスクおよびプレーヤを実現することができた.

Real-Time Recording and Erasure of Information by Optical Head with Laser Diode Array in Magneto-Optical Disk

The realization of an optical data system using magneto-optical disks remains an important subject for research. The functions of such a system would consist of real-time recording and erasure of information. We developed an optical head using a laser diode array with three elements, which successfully performs these functions. We also measured the real-time recording/erasure characteristics as a function of the composition of TbFeCo disks, using the optical head and six TbFeCo disks with different compositions. The characteristics were evaluated on the basis of the carrier-to-noise ratio and block error rate in Compact Disc formats. Real-time recording/erasure could be performed by applying a magnetic field of more than 400 Oe. But TbFeCo disks with compositions in the neighborhood of the magnetic compensation point delivered more stable performance with respect to deviations in the applied magnetic field and the recording power than disks with other compositions. We concluded that TbFeCo disks with 23 to 27 at% Tb are optimal for real-time recording/erasure by an optical head using a laser diode array.