Hitachi, Ltd.

Hitachi Video Eng. Inc.

Nobutaka Ohnuki

Akira Arimoto

Naoki Chinone

Masahiro Ojima

Takashi Kimura

Junichi Ikoma

In reproducing recorded information from a track on an optical disc by the use of a light beam, a tracking servo is employed for enabling the light beam to follow up the track. When there occurs any tracking deviation due to some flaw or the like on the track, the tracking servo is switched off if the number of times of such tracking deviation has exceeded a predetermined value within a preset time, and simultaenously a braking action is executed to impede the movement of the light beam. The braking force is adjustable in accordance with the velocity of the light beam movement.

Tracking control unit in information reproducing apparatus

In an apparatus for reproducing information recorded on a disk having a tracking servo device for an actuator which directs a read beam to a track of the disk, a first power product is applied to the actuator upon turn-off of the tracking servo system, a velocity of the actuator is detected based on an error signal from the tracking servo device, the velocity of the actuator detected immediately after the start of movement of the actuator is stored, on the basis of the detected result, the subsequent velocity of the actuator is sequentially compared with the initial velocity and the velocity is controlled at a constant value until the actuator reaches a predetermined track.

Apparatus for reproducing information recorded on a disk

In order to suppress laser noise, a semiconductor laser oscillating in a single mode under direct-current drive is driven by a signal with a high frequency current superposed on a direct current. In particular, the laser is driven to be brought into continuous wave pulsed oscillation at a pulse width of at most 1.2 ns to achieve the desired noise suppression.

Method of and apparatus for driving semiconductor laser

An electro-acoustic transducer having a flat sound radiating plane is disclosed, in which a voice coil bobbin having a voice coil wound around an outer circumference thereof is inserted in an air gap defined by an inner pole piece and an outer pole piece and dome-shaped diaphragm is inserted in the voice coil bobbin to define a front chamber surrounded by curved surfaces of an outer surface of the diaphragm and an inner surface of the voice coil bobbin, and foamed synthetic resin is filled in the front chamber.

Growing community of inventors

Tokyo, Japan

Nobutaka Ohnuki