Isao Hoshino

Development of Two-Axis Actuator with Small Tilt Angles for One-Piece Optical Heads

An integrated one-piece optical head for optical disk drives is effective for reducing the head size and tracking error signal offset. The authors have developed a two-axis actuator which can drive a one-piece optical head with small tilt angles by compensating the torque which has two main components acting in opposite directions; one originates from the focusing driving coil and the other from the tracking coil. The tilt angle of ±0.8 mrad was achieved when the extent of actuator movement was ±0.5 mm in the focusing direction and ±0.4 mm in the tracking direction.

Optical Disk Memory System

An Optical Disc Memory System has been developed. This system is designed for document storage and retrieval by analysing the memory system parameters, including data format and signal processing, linear actuator and access sequence, statistical error characteristics in the storage medium, and so on. The storage capacity is more than 10,000 letter-size documents on one side of a 300 mmØ disc. Every document can be randomly accessed in less than 0.7 second. System erorr rate is on the 10 -8 level.

Development of Optical Pickup for Digital Versatile Disc Using Two-Wavelength-Integrated Laser Diode

A digital versatile disc (DVD)-and compact disc (CD)-compatible optical pickup using a two-wavelength-integrated laser diode (TWIN-LD) has been developed. The TWIN-LD has two emission points in one chip, one for the red laser beam to read out signals from DVDs and the other for the IR laser beam to read out signals from CDs that are arranged along the active layer. With the application of a TWIN-LD to the optical pickup, the necessity for four optical components, namely, a laser diode, photodetector, holographic optical element and dichroic prism, is avoided in comparison with conventional optical pickups. This paper discusses some key points for designing an optical system using a TWIN-LD, and the results of the experiments appling the optical system to an optical pickup 7.3 mm in height.

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.

Focusing-Error Detection Using a Mixed-Aberration-Generating Holographic Optical Element

A new focus error detecting method for an optical disk drive has been developed using a holographic optical element (HOE). The groove pattern on the HOE was designed using the ray-tracing and least-squares-fitting methods to attain a symmetric beam profile. It has been proven successfully that this method of focus error detection is insensitive to wavelength fluctuations, objective lens shifts, and tracking grooves.

130mm.PHI. magneto-optic disc memory.

光磁気ディスクメモリーが現行の磁気メモリーと同様に世の中で広く使われるためには, 記録媒体の信頼性ならびに情報の重ね書きの問題を解決することが現在最も重要な技術課題となっている.我々は, 従来のFe系記録材料に比べて長寿命のTbCo膜を記録膜に用いることで媒体の信頼性向上を図り, 消去用と記録用の2光磁気ヘッド方式とすることで磁気メモリーと同様に情報の重ね書きを可能にした130mmφ光磁気ディスクメモリー装置を開発した.光磁気ヘッドの小型化, セクタ構造と2ヘッドのアクセス方向の工夫により, 装置全体を5.25インチ標準磁気ディスクドライブと同じサイズに収めている.本装置は2ヘッド構成でほぼ実時間で情報の重ね書きができることから, 卓上型や個人用のコンピュータの汎用外部メモリーのみならず, 書き換え可能なコンパクトディスク (CD) やビデオディスク (VD) へも応用できる.