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Abstract

The present invention describes a time based servo pattern scheme which provides position and velocity information with high accuracy. A plurality of servo lines are formed on a data disk extending from the inner track to the outer track. In the preferred embodiment of the present invention, these lines are employed as part of a buried servo scheme such that the entire useable disk surface is dedicated to data storage. The servo pattern is written on each side of the disk so that, if the disk were transparent, the respective servo lines would appear to intersect when viewed from above. Servo heads located on each side of the disk detect servo line crossings. By comparing the time difference between crossings of corresponding tracks on either side of the disk, the radial position of the heads can be determined. Therefore, even when nominal track centers do not fall on servo line intersections, their position can be determined accurately. Thus, the servo pattern of the present invention is track pitch independent. A concentric calibration track is formed on the disk surface so that offsets between the desired servo and data head positions may be detected and compensated.

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First Claim