Magnetic head tracking control method, servo signal verification method, magnetic tape drive, and servo writer

A method for verifying quality of a servo signal written in a perpendicular recording-type magnetic tape, in which servo signal a magnetic pattern is repeatedly arranged in a longitudinal direction of the magnetic tape at predetermined intervals, the magnetic pattern being composed of a first portion magnetized in one direction that is one of two opposite thickness directions and a second portion magnetized in a direction opposite to the one direction, the method comprising the steps of:

• reading out the servo signal and acquiring, from the readout servo signal, a waveform of the servo signal in which a unit waveform having a pair of peaks of opposite polarities corresponding to the magnetic pattern appears periodically, the unit waveform being composed of a crest portion and a trough portion, the unit waveform being composed of a crest portion and a trough portion;
• selecting, from between the crest portion and the trough portion of the unit waveform contained in the acquired waveform of the servo signal, a portion of the waveform containing one of the peaks located rearwardly in a tape transport direction in a time of writing the servo signal;
• and
• verifying the quality of the servo signal based on the selected portion of the waveform.

A magnetic tape drive for recording and/or retrieving information in a perpendicular recording-type magnetic tape with a servo signal written therein, in which servo signal a magnetic pattern is repeatedly arranged in a longitudinal direction of the magnetic tape at predetermined intervals, the magnetic pattern being composed of a first portion magnetized in one direction that is one of two opposite thickness directions and a second portion magnetized in a direction opposite to the one direction, the magnetic tape drive comprising:

• a magnetic head including a first element configured to record and/or retrieve information in the perpendicular recording-type magnetic tape, and a second element configured to read out the servo signal;
• a waveform acquisition unit configured to acquire, from the servo signal read out by the second element, a waveform of the servo signal in which a unit waveform having a pair of peaks of opposite polarities corresponding to the magnetic pattern appears periodically, the unit waveform being composed of a crest portion and a trough portion;
• a waveform selection unit configured to select, from between the crest portion and the trough portion of the unit waveform contained in the waveform of the servo signal acquired by the waveform acquisition unit, a portion of the waveform containing one of the peaks located rearwardly in a tape transport direction in a time of writing the servo signal;
• and
• a position control unit configured to regulate a position of the magnetic head based on the crest or trough portion of the waveform selected by the waveform selection unit.

A servo writer for writing a servo signal in a perpendicular recording-type magnetic tape, in which servo signal a magnetic pattern is repeatedly arranged in a longitudinal direction of the magnetic tape at predetermined intervals, the magnetic pattern being composed of a first portion magnetized in one direction that is one of two opposite thickness directions and a second portion magnetized in a direction opposite to the one direction, the servo writer comprising:

• a write head configured to write the servo signal in the perpendicular recording-type magnetic tape;
• a signal output unit configured to output a pulsed signal to the write head;
• a read head provided in a position downstream relative to the write head along a path traveled by the perpendicular recording-type magnetic tape, the read head being configured to read out a servo signal;
• a waveform acquisition unit configured to acquire, from the servo signal read out by the read head, a waveform of the servo signal in which a unit waveform having a pair of peaks of opposite polarities corresponding to the magnetic pattern appears periodically, the unit waveform being composed of a crest portion and a trough portion;
• a waveform selection unit configured to select, from between the crest portion and the trough portion of the unit waveform contained in the waveform of the servo signal acquired by the waveform acquisition unit, a portion of the waveform containing one of the peaks located rearwardly in a tape transport direction in a time of writing the servo signal;
• and
• a signal verification unit configured to verify a quality of the servo signal based on the crest or trough portion of the waveform selected by the waveform selection unit.