Hitachi, Ltd.

Hitachi Video and Information Systems, Inc.

Hisamitsu Tanaka

Motoyuki Suzuki

Yoshio Suzuki

Masayuki Inoue

Hisataka Sugiyama

Makoto Miyamoto

Tetsuya Fushimi

Kunikazu Ohnishi

Yukio Fukui

Masaaki Kurebayashi

Yoshio Miura

Toru Kawashima

Junji Nakajima

Hiroyuki Minamura

For a disk of a land/groove scheme with land tracks and grooves appearing alternately, in order to enable stable and reliable reproduction of information as recorded on a disk by stably and reliably detecting a specific position at which a land track and groove change therebetween, a technique is employed for detecting the position whereat one land track is changed to a groove, or vice versa, by utilizing an HPP signal rather than an RF signal in cases where an optical head 103 attempts to reproduce certain information at the pit formation position of a disk 101. In addition, detect the polarity--positive or negative--of a pit signal appearing in the HPP signal, and then detect the position whereat the land track and groove change therebetween based on the position at which the order or sequence thereof changes, thereby permitting effectuation of optical head's tracking control and focus control by a method suitable for its respective parts.

Method and apparatus for detecting position of alternated land and

A masking type light control layer for decreasing its reflection factor in a high-temperature region is formed on phase pits of an optical disc, and the phase pit depth is set to a predetermined value. A light spot for reproduction is shaped to an elliptical form and two sub-flux beams on the optical disc are spaced by 5/4 track pitch from a principal flux beam in the radial direction of the optical disc. The kind of optical disc is discriminated and reproduction laser power and characteristics of an equalizer circuit are switched in accordance with the type of an optical disc. Through this, a stable servo signal detection can be ensured and repetitive reproduction characteristics can be improved.

Optical disc with phase pits and a reproducing apparatus for data

A tracking control apparatus is provided for controlling a displacement error between a pickup system and a track when reproducing information recording on an information-recording and reproducing medium having tracks on which information is recorded or reproduced. The tracking control apparatus includes on-track detecting means for detecting a light beam is located on the track, traveling-direction detecting means for detecting the direction of the pickup system traveling toward the track from the displacement error and the output signal supplied by the on-track detecting means and outputting a traveling-direction signal representing the traveling direction, track-slippage detecting means for detecting a track-slippage signal representing the direction of the light beam being slipped out of a target track from the traveling-direction signal supplied by the traveling-direction detecting means, and tracking control means for supplying as a control signal the displacement error when the light beam is located on the target track or as a control signal the track-slippage signal supplied by the track-slippage detecting means when the light beam is not spotted on the target track and driving the pickup system in a manner to allowing the light beam to follow the tracks.

Tracking control apparatus for controlling the tracking of a target track

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Yokohama, Japan

Hisamitsu Tanaka