Funai Electric Company Ltd.

Yoshiaki Ukawa

Teruaki Sogawa

Yasunori Kuwayama

Toyoshi Nogami

Ryotaro Nakagawa

Katsuichi Inoue

Takashi Kasahara

A defocus amount specifying circuit specifies, as a focus error minimum defocus amount FMDF, a defocus amount by which the amplitude of a focus error signal becomes minimum in a state in which tracking servo is off in a period after insertion of an optical disc and before a seek operation, and specifies, as a jitter minimum defocus amount JMDF, a defocus amount by which a jitter amount becomes minimum in a state in which tracking servo is on. A defocus amount supplying circuit transmits the focus error minimum defocus amount FMDF to a focus servo circuit to perform focus control during a seek operation, and transmits the jitter minimum defocus amount JMDF to the focus servo circuit to perform focus control after the seek operation.

Optical disc playback apparatus performing defocus adjustment of objective lens

An optical pickup of an optical disc apparatus has a lens holder for holding an objective lens is pivoted with a guide shaft slidably in a direction in parallel with an optical axis of the objective lens and rotatably around the guide shaft in a direction perpendicular to the optical axis. For focusing a laser beam on a data recording face of an optical disc in a focusing on operation, a wobble signal of rectangular waveform having a predetermined voltage and a predetermined frequency is applied to a tracking coil for reciprocally displacing the lens holder in the direction perpendicular to the optical axis, while a focusing coil is driven for moving the lens holder in the direction in parallel with the optical axis. Thus, the lens holder can be moved smoothly along the guide shaft, so that the possibility of failure of the focusing the laser beam on the optical disc can be reduced drastically.

Optical disc apparatus

A controller configures a balance position of a tracking error signal at a point at which an error rate indicates a minimum value while the balance position of the tracking error signal from an optical pickup is shifted from the center in reproducing the optical disk. Therefore, even when a pit on the track of the optical disk is asymmetrical with respect to the center, the error rate in reproducing the optical disk is reduced and the precision of the reproducing signal is enhanced.

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Osaka, Japan

Yoshiaki Ukawa