Patent ID: 7911728
Filing Date: 2011-03-22
Classification: G11B

Abstract:
1. A method for writing servo information on a perpendicular magnetic recording disk with a system that includes a processor, a spindle for rotating the disk, a read head and a write head, and an actuator responsive to a control signal for moving the read head and write head across the disk, the disk having a plurality of generally concentric circular data tracks radially spaced by a track pitch (TP) and containing discrete magnetizable data dots, and a plurality of servo sectors extending generally radially across a plurality of the data tracks and containing discrete magnetizable dots, each of the plurality of servo sectors including a position error signal (PES) alignment pattern of a plurality of circumferentially-spaced alignment fields, each alignment field comprising discrete magnetizable dots forming a pattern of dots extending generally radially across the tracks, the dots in each alignment field being arranged in circumferential segments, each segment being radially spaced from adjacent circumferential segments, wherein each alignment field is radially shifted from circumferentially adjacent alignment fields by a fixed fractional portion of TP, the method comprising: magnetizing all of the dots in all of the alignment fields of the PES alignment pattern in the same perpendicular direction; rotating the disk while the read head generally follows a data track centerline; detecting with the read head a readback signal from the alignment fields in the servo sectors as the disk rotates; calculating, from the readback signal from the alignment fields in each servo sector, a radial offset of the read head relative to a data track centerline for each servo sector; using the calculated offsets to adjust the radial position of the write head to cause the write head to follow a data track centerline while the disk is rotating; while the write head is following a data track centerline, magnetizing dots in the servo sectors according to a predetermined pattern; moving the write head radially a fractional part of TP; causing the write head to follow a track that is radially shifted from a data track centerline by said fractional part of TP; and while the write head is following said radially shifted track, magnetizing dots in the servo sectors according to a predetermined pattern.