| 摘要 |
PURPOSE:To minimize a bias magnetic field impressing means by setting the setting direction of a magnet field generating means in order that the relief of a vertical component in a beam radiating position on a disk of a leakage field generated in the magnetic field generating means except the bias magnetic field impressing means becomes zero. CONSTITUTION:When a permanent magnet 44 is set to be in an S pole and front and back yokes 42 and 43 are set to be in an N pole, a magnetic circuit for VCM (voice coil motor), whose component along the optical axis of a light beam is turned upward, works to negate the leakage field from a lens actuator 20. A clamp hub 53 consists of a magnetic substance and fixes a disk 6 with a magnetic attractive force between the permanent magnet 54 of a turntable 52 and the hub 53. Since the permanent magnet 54 is set in the S pole so as to negate the leakage field, the leakage field of the lens actuator part 20 is reduced by interfering in the leakage fields of the VCM and a clamp means. Thus, it is no needed to generate an extra magnetic field, so that the bias magnetic field impressing means can be minimized.
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