Method and apparatus for controlling an optical head relative to an initial track and a target track on a storage medium having data arranged thereon in tracks

Abstract

A method for moving an optical head from an initial track to a target track on a storage medium having data arranged in tracks thereon. The method includes determining a track crossing number indicating a number of tracks between the initial track and the target track, moving the optical head from the initial track toward the target track, and measuring a reflectivity level of light from the medium. The method continues with deriving a tracking error signal responsive to the reflectivity level. A waveform of the tracking error signal has zero crossings corresponding to the optical head crossing one of the tracks. The method may further include incrementing a track count number for each the zero crossing, and passing the reflectivity level through a high pass filter to obtain a data indicator signal. In this embodiment, a waveform of the data indicator signal has indicator points corresponding to the zero crossings. The method may conclude by decrementing the track count number for each the zero crossing corresponding to changes in the reflectivity level in response to the data, and terminating the step of moving the optical head when the track count number equals the track crossing number. In an alternative method, the passing step may be replaced with deriving a data indicator signal responsive to the reflectivity level. Apparatus for controlling an optical head according to the present methods include a tracking error signal generator, a preamplifier, a track/hold sector, and a track crossing signal generator.