Abstract: The servo positioning and tracking system of an optical disk drive utilizes the tracking error signal on a continuous, closed loop basis to move the optical beam from one track on the disk to an adjacent track. A circuit generates a ramp waveform that is used to introduce a controlled offset into the tracking servo. The servo error signal derived from pre-formatted fine tracking features on the disk is inverted in phase when the read beam is moving between the tracks. This allows the tracking servo loop to remain closed and stable at all times. The ramp waveform is generated based on tracking error information stored from the previous micro-jump, i.e., a single-track change in read beam position. The peak tracking error signal is stored by a peak sense and hold circuit, and used to adjust the amplitude of the ramp waveform. Peak tracking error information allows the precise motion of the read spot and provides the proper timing to switch polarity of the tracking error signal read from the disk.

Abstract: A linear actuator for controlling access to a track element belonging to a plurality of adjacent track elements arranged in a reference surface of an optical disk rotatable about a spindle. The linear actuator includes an objective lens for projecting a light spot for interaction with a selected one of the track elements. A first moving mechanism is provided for supporting the objective lens for movement along a first direction substantially perpendicular to the reference surface for controlling the focusing of the light spot. A second moving mechanism in the linear actuator supports the objective lens for movement along a second direction substantially parallel to the reference surface and generally transverse to the track elements for controlling the access thereto. The second moving mechanism includes a pair of spaced apart, parallel rods which extend generally transverse to the track elements. The rods have a round cross-section and are made of a ferromagnetic material.