Abstract: An actuator assembly for use in an optical disk information processing system is disclosed having improved performance characteristics for achieving a large radial movement frequency bandwidth. The actuator assembly includes an actuator body defining a rail channel for movement on a single rail. The device is configured so that the center of mass of the actuator body is above the friction surfaces between the rail and the rail channel. The actuator body includes an optical channel for receiving an optical beam to be focused on an optical disk. This optical channel is positioned between two focus supports which support a lens holder which is movable for focusing the incoming optical beam onto the optical disk. The focusing motor, including a coil and focusing magnets, is positioned below the center of mass of the actuator to achieve a balanced device. The radial drive assembly for the device includes a coil directly wound on the actuator body which encircles the optical channel and the rail channel.