Importance

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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.

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First Claim