Patent ID: 7542384
Filing Date: 2009-06-02
Classification: G11B

Abstract:
1. An objective lens actuator, comprising: a ferromagnetic yoke including two inner yokes; an objective lens holder movably located on the ferromagnetic yoke corresponding to the inner yokes for holding an objective lens; two tracking coils and two focusing coils which are respectively located on two opposite sides of the objective lens holder and located on the other two opposite sides of the objective lens holder and surrounded with the two inner yokes; a magnetic element set located on the ferromagnetic yoke corresponding to the tracking coils and the focusing coils to generate a magnetic field perpendicular to the optical axis of the objective lens; a suspension wire set connecting to the objective lens holder, the tracking coils, and the focusing coils to hang the objective lens holder and channel current to the tracking coils and the focusing coils; a damper holder located on the ferromagnetic yoke to allow the suspension wire set to pass through; and a printed circuit board located on the damper holder and surrounded with the suspension wire set to provide the current to the tracking coils and the focusing coils to drive the objective lens holder, wherein the magnetic element set includes a first magnetic element unit and a second magnetic element unit, the first magnetic element unit having a magnetic flux parallel with a normal direction of the an area which the tracking coils surround, the second magnetic element unit corresponding to the focusing coils and having a magnetic flux perpendicular to the first magnetic element unit, and wherein the first magnetic element unit includes a first portion and a second portion, the first portion having two opposing first magnetic elements, the second portion having two opposing second magnetic elements, the magnetic flux direction of the first magnetic elements from the N pole to the S pole being coincided with the direction from the ferromagnetic yoke to the objective lens holder, the magnetic flux direction of the second magnetic elements from the N pole to the S pole being coincided with the direction from the objective lens holder to the ferromagnetic yoke, the second magnetic element unit including two third magnetic elements that have a magnetic flux direction from the N pole to the S pole coinciding with the direction from the ferromagnetic yoke to the objective lens holder, and from the objective lens holder to the ferromagnetic yoke to make the magnetic flux direction of each of the third magnetic element and the magnetic flux direction of the second magnetic element the same as the direction from the ferromagnetic yoke to the objective lens holder, or the direction from the objective lens holder to the ferromagnetic yoke.