| 摘要 |
PURPOSE:To keep always constant control sensitivity by unitedly constituting a yoke for an accessing mechanism, a yoke for a tracking mechanism and/or a yoke for a focusing mechanism. CONSTITUTION:In the tracking mechanism constituted of a tracking coil 3, a magnetic circuit 31 for tracking and a yoke 6, the focusing mechanism constituted of a focusing coil 4, a magnetic circuit 41 for focusing and a yoke 6 and an accessing mechanism constituted of an accessing coil 5, a magnetic circuit 51 for accessing and a yoke 6, the yokes 6 to be auxiliary magnetic poles of respective magnetic circuits are unitedly formed and rigidity is increased over the whole area of the moving ranges of the coils. Thereby, change or distortion is not generated in the gap between the yoke 6 and each magnetic circuit. Consequently, respective coils can be driven with stable and uniform sensitivity over the whole area of the moving ranges.
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