Patent ID: 7835234

Claim:
An objective lens driving device comprising: an objective lens; a lens holder which holds the objective lens; two magnets which are disposed facing each other to sandwich the lens holder; focusing coils which are fixed on the lens holder to generate driving force in focusing direction by electromagnetic force action with the magnets; tracking coils which are fixed on the lens holder to generate driving force in tracking direction by electromagnetic force action with the magnets; and an elastic supporting member which supports the lens holder in movable manner, wherein on each of surfaces that face the two magnets, respectively, of the lens holder, one of the focusing coils and two of the tracking coils are set up to align in a direction that is parallel to the tracking direction with the focusing coil being as a center, the two magnets are identical multipole magnetized magnets and are disposed such that one upside down relative to the other, the multipole magnets are composed of a first region which has a rectangular parallelepiped shape, a second region which is formed around the first region to have a substantially U shaped cross section and has an opposite N-S polarity with respect to the first region, and a third region that is composed of two rectangular parallelepiped shaped regions which are formed to sandwich the second region and that has the same N-S polarity with respect to the first region, of two effective portions which are opposite sides of the focusing coil and that generate the driving force, one is disposed to face the first region and the other is disposed to face the second region, and of two effective portions which are opposite sides of the tracking coils and that generate the driving force, one is disposed to face the second region and the other is disposed to face the third region.