Sony Corporation

Koso Kashima

Kenji Yamazaki

Yoshimasa Sato

Taizo Takiguchi

Test pattern data is recorded on a track of the optical disc, and the other pattern data is recorded on the neighboring track. A focus bias value providing the minimum jitter amount when the test pattern data is reproduced with varying the focus bias, is obtained. Just focusing condition is attained by the focus servo using the focus bias. When the test pattern data is reproduced, the data of these neighboring track is also reproduced simultaneously because the pattern data of the type different from the test pattern data is also recorded on the neighboring track. Particularly, under the defocusing condition, crosstalk amount becomes larger because the beam shape is distorted. With reference to jitter amount, such a mistake that the defocusing condition is erroneously determined as the just focusing condition can be eliminated. That is, the focus servo signal providing the accurate just focusing condition can be obtained.

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Kanagawa, Japan

Koso Kashima