Close tracking algorithm in a digital tracking servo system

摘要

A close tracking algorithm for a tracking servo system is disclosed. The track crossing rate of an optical pick-up unit positioned over an optical media is determined. When the track crossing rate is below a threshold value, then a tracking servo algorithm is enabled. The tracking servo algorithm provides control signals to control an actuator arm that controls the position of the optical pick-up unit over the tracks of the optical media. In some embodiments, the track crossing rate can be determined by monitoring the zero crossings of a tracking error signal derived from optical signals measured in the optical pick-up unit.