Spiral pitch correction based on micro-jog variation

摘要

During a self-servo write process, servo sectors that have uniform radial spacing are written on a disk surface. As part of the in-drive writing of the servo sectors, a radial offset between a reader element and a writer element of a magnetic head is measured. The measured radial offset, or micro-jog, is compared to a known nominal micro-jog value for the current radial position of the magnetic head. When the measured micro-jog value does not match the nominal micro-jog value, an appropriate correction to the self-servo write step size is applied to the radial spacing between the servo sectors being written. Variations from ideal servo spiral slope that are inherent in some servo spirals can be compensated for, thereby improving the uniformity of radial spacing of data tracks associated with the servo sectors.

主权项

1. A method of writing servo information on a surface of a magnetic disk with a magnetic head having a read head and a write head that is offset from the read head by a fixed distance, the method comprising:
writing servo sectors defining a first set of data tracks on the surface of the magnetic disk using the write head, wherein the write head is positioned during the writing of the first set of data tracks according to positioning signals generated by the read head; measuring a radial offset between the write head and the read head when the magnetic head is positioned over the first set of data tracks; determining a track pitch adjustment based on a difference between the measured radial offset and an expected radial offset when the magnetic head is positioned over the first set of data tracks; and writing servo sectors defining a second set of data tracks on the surface of the magnetic disk using the write head, wherein the write head is positioned during the writing of the second set of data tracks according to positioning signals generated by the read head and the track pitch adjustment, wherein the track pitch adjustment is selected to reduce track pitch when an absolute value of the measured radial offset is less than an absolute value of the expected radial offset, and the track pitch adjustment is selected to increase track pitch when the absolute value of the measured radial offset is greater than the absolute value of the expected radial offset.