| 摘要 |
PURPOSE:To reduce the vertical reaction due to eccentricity between a magnet and a yoke, etc., and to keep good sliding characteristic by forming rugged grooves on the opposite face of the base yoke facing the annular permanent magnet. CONSTITUTION:A focusing control coil 11 and tracking control coils 10a and 10b are attached to the inside and the outside of a base yoke 2, and an annular permanent magnet 6 fixed to a movable holder 1 is arranged prescribed gaps apart between them. The face of the base yoke 2 facing the magnet 6 is provided with grooves consisting of projecting parts 21 and recessed parts 20 and the force applied to the inside and the outside of the permanent magnet by eccentricity or the like is almost canceled because the magnetic flux density is reduced in recessed parts 20 and is raised in projecting parts 21. Consequently, the vertical reaction intersecting orthogonally with a supporting shaft 8 is reduced at the time of the occurrence of eccentricity between the magnet 6 and the yoke 2, etc., and good sliding characteristic is secured. |
