US Patent 7397732 Objective lens driving apparatus and optical disc apparatus

The invention provides an objective lens driving apparatus in which an efficiency of a magnetic circuit is improved by making a magnetic flux density distribution of the objective lens driving apparatus close to symmetrical. An objective lens driving apparatus has an objective lens, a tracking coil driving the objective lens in a tracking direction, a focusing coil driving the objective lens in a focusing direction, and a yoke arranged so as to oppose to the tracking coil and having a permanent magnet attached thereto. The yoke has a bottom plate portion and an outer yoke bent approximately perpendicularly to the bottom plate portion from an outer edge portion of the bottom plate portion, has a first yoke having an opening formed in a center portion thereof, and a second yoke having a bottom plate portion and an inner yoke bent approximately perpendicularly to the bottom plate portion from an inner edge portion of the bottom plate portion, and having an opening formed in a center portion thereof.