Patent ID: 8169864

Claim:
An actuator for a pickup, comprising: a fixed portion; a movable portion designed to be movable in each of a focusing direction extending along an optical axis of an objective lens and in a tracking direction substantially perpendicular to the focusing direction, due to a driving force transmitted from a drive portion, for holding the objective lens; and four linear elastic members each having ends connected to the movable portion and the fixed portion, respectively, wherein the ends of the four linear elastic members are located on a virtual circle formed on a plane by being projected onto a plane including both the focusing direction and the tracking direction, the ends are linked with one another by line segments constituting substantially a trapezoidal shape, and the virtual circle has a center defined as a rolling center, which coincides with at least one of a center of gravity of the movable portion, a center of a driving force of the movable portion, and a center of translational forces of the linear elastic members, wherein the four linear elastic members are composed of the two linear elastic members linked with each other by a line segment constituting an upper base of the trapezoidal shape, and two linear elastic members linked with each other by a line segment constituting a lower base of the trapezoidal shape, and the former two linear elastic members are different in cross-sectional area from the latter two linear elastic members.