An actuator used with an optical pickup to drive a blade, on which an
objective lens is mounted, in focusing and tracking directions, includes a
pair of magnets installed on a base, and a plate coil installed in the
blade to be placed between the magnets. Each magnet has a shape in which N
and S poles of the magnet are alternately magnetized in four regions
asymmetrically split vertically and horizontally. In this structure, the
actuator used with an optical pickup can be less affected by sensitivity
variations when the blade is displaced, and the size of the
electromagnetic driving unit can be reduced by reducing the number of
magnetized gaps formed in the magnet.
