Matsushita Electric Industrial Co., Ltd.

Atsushi Miyazaki

Chikashi Inokuchi

Toshiya Akagi

Shigeru Furumiya

Hiroyuki Yamaguchi

Yuji Hisakado

Yoshiyuki Miyabata

A power control device for controlling a power of a light source of an optical beam directed to an optical medium. The power control device includes a reflected light detector for detecting reflected light from the optical medium when irradiated by an optical beam which is following a track; an arithmetic unit for calculating from the reflected light a transmissivity of light transmitted from a disk surface to a recording layer or an amount of directed light on the recording layer of the medium; and power control means for controlling the power of the light source for emission based on a calculation result produced by the arithmetic unit.

Laser power controller and optical disk device

An optical disc recording/reproducing apparatus includes: recording/reproducing means for recording/reproducing information by emitting a light beam onto a disc having a track which wobbles at a predetermined frequency; reflected light detection means for detecting the light beam reflected from the disc; wobble signal detection means for detecting a wobble amplitude signal which represents an amplitude of a signal generated from a component which is extracted from an output of the reflected light detection means and which wobbles at the predetermined frequency; and variation rate detection means for detecting dirt adhered on the disc based on a rate of a variation in the wobble amplitude signal, wherein the variation rate detection means detects the dirt based on the wobble amplitude signal before the recording/reproducing means records/reproduces the information.

Optical disk recording/reproduction apparatus with a detection means for detecting dirt on the optical disk

A laser power control method according to the present invention is a method for controlling an output power of a laserwhich is used for recording information on a recording medium. The method comprises steps of: detecting emitted light of the laser by a first detection section; obtaining a first driving current of the laser by a first control sectionbased on an output of the first detection section; detecting reflected light or transmitted light from the recording medium by a second detection section; and obtaining a second driving current of the laser by a second control sectionbased on an output of the second detection section. The laser is driven based on the first driving current or the second driving current while the first control section and the second control section are operated alternately such that the second control section does not operate when the first control section is operating, and the first control section does not operate when the second control section is operating. With such a structure, even when a plurality of laser powers which are switched at a high speed are required for recording of information, each laser power can be controlled so as to be an appropriate power for recording of information.

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Kyoto, Japan

Atsushi Miyazaki