| 摘要 |
PURPOSE:To position correctly a head regardless of an eccentric rotation of the recording medium by obtaining a data track position, which goes to be the positioning target of a reading head, based upon a track pitch and correcting a target position based upon the eccentric quantity of a reference track determined by the rotational angle of the recording medium. CONSTITUTION:A rotational angle from a reference position of recording medium 1 during the rotation is determined by a rotational angle detecting means 6, the position of a positioning track 9 and a reference track 10 for counting a pitch in a reference rotational angle 8 is counted by a position detecting means 7 from the output of a reading head 2, and the pitch of respective data tracks 11 is obtained at a track pitch calculating means 13. The eccentric quantity of the track 9 as a function of the rotational angle is obtained by an eccentric quantity calculation means 16 from the position of a reference track 9 in plural set rotational angles 14. To a target position of the data track obtained based upon a track pitch 12 at a target position setting means 17, the correction of an eccentric quantity 15 is added by a target position correcting means 19, and the head 2 is positioned through a control target value output means 22 and a head driving system 4.
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