Hitachi, Ltd.

Yasuhiro Mii

Takashi Yoshida

Fujio Tajima

Atsushi Okuyama

Masato Soma

Masamichi Ito

Hidehito Yamada

A positioning system of an optical disc apparatus includes focus error detecting part for detecting a focus error signal as a focal shift of a light spot related to an information recording surface of an optical disc, light spot moving part in the direction intersecting substantially perpendicularly to the optical disc surface, first digital arithmetic part for receiving the focus error signal and outputting a first control signal, second digital arithmetic part for receiving the focus error signal and a specified third control signal, performing arithmetic operations of a disturbance observer and outputting a second control signal, adding circuit for adding the first control signal and the second control signal and outputting the third control signal, drive circuit for driving the light spot moving part in a direction intersecting perpendicularly to the disc surface by the third control signal, wherein the first and the second digital arithmetic circuit perform arithmetic operations at different sampling periods.

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Ibaraki-ken, Japan

Yasuhiro Mii