Apparatus and method of detecting head position error in magnetic disk

Abstract

In a disk drive for detecting a position error distance of a head with respect to a measuring cylinder by reading servo data recorded on the measuring cylinder on a data surface of a disk, an apparatus and method of detecting a position error of a data head are provided which comprises repeatedly reading patterns written in advance relating to a plurality of kinds of servo data in at least three regions on the outer or inner peripheral side of the measuring cylinder or in both of them, and comparing the read results and detecting an accurate position error distance of the data head. More preferably, the apparatus and method include reading a plurality of kinds of patterns written in advance relating to servo data in at least three regions on the outer and inner peripheral sides of the measuring cylinder, detecting a rough position error distance of the data head from the measuring cylinder on the basis of part of the combinations of a plurality of kinds of patterns, and detecting a detailed position error distance of the data head on the basis of other part of combination of a plurality of kinds of patterns. Further preferably, the apparatus and method include alternately reading a plurality of kinds of patterns in two phases.