Optical disk apparatus performing correction of phase difference

Details Optical disk apparatus performing correction of phase difference Optical disk apparatus performing correction of phase difference

1997-09-17

2000-02-22

Tran, Thang V.

Dynamic information storage or retrieval

With servo positioning of transducer assembly over track...

Optical servo system

369 4429, 369 4432, G11B 709

Patent

active

060288264

ABSTRACT:
An optical disk apparatus includes a rotating device for rotating a recording medium at a prescribed reproduction rate. A converging device converges a light beam on the recording medium. A moving device moves the converging device so as to cause the converged light beam to cross a track of the recording medium. A light detection device has four areas for receiving light reflected by the recording medium and respectively outputting first, second, third and fourth detection signals. A phase correction device outputs first and second correction signals respectively by correcting the phase of the first and second detection signals in accordance with a correction amount. A tracking error detection device detects a positional offset between the converged light beam and the track based on a phase difference between first and second addition signals and outputs a tracking error signal indicating the positional offset. The first addition signal is obtained by adding the first correction signal and the fourth detection signal. The second addition signal is obtained by adding the second correction signal and the third detection signal. A tracking control device performs feedback control of the moving device so that the light beam converged on the recording medium is positioned on the track, based on the tracking error signal. An adjustment device adjusts the correction amount for the phase correction device based on an asymmetry level based on the tracking error signal without causing the tracking control device to perform feedback control.

REFERENCES:
patent: 5610886 (1997-03-01), Hayashi et al.
patent: 5663942 (1997-09-01), Ishibashi et al.
patent: 5751674 (1998-05-01), Bradshaw et al.
patent: 5751675 (1998-05-01), Tsutsui et al.
patent: 5761164 (1998-06-01), Abe et al.

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