Sharp Kabushiki Kaisha Corporation

Tetsuo Fujiwara

Hiroshi Fuji

Toshihisa Deguchi

Takashi Iwaki

Shozou Kobayashi

A beam controller for controlling a semiconductor laser provided in an optical recording/playback apparatus includes first and second current sources for driving the semiconductor laser at a low level (play-back mode) and/or at a high level (recording or erasing mode). The first and second current sources are controlled to have stable power automatically by a first and second auto-power circuits, respectively. The first and second auto-power control circuits include a sample-hold circuit which stores an output signal from a low-pass filter. This enables the beam controller to avoid the transition response problems of the low-pass filter. A switching circuit is also included to select either the stored low-pass filter signal on the present low-pass filter signal.

Beam controller for magneto-optical disc memory system

A beam controller for controlling a semiconductor laser included in an optical recording-play-back apparatus. The beam controller is comprised of first and second current sources for driving the semiconductor laser at a low level during a play-back mode and at a high level during an erasing mode. The first and second current sources are respectively automatically controlled by a first and second auto-power control circuit to provide stable power outputs.

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Tenri, Japan

Tetsuo Fujiwara