Patent ID: 7630155
Filing Date: 2009-12-08
Classification: G11B

Abstract:
1. An eccentricity correction method comprising: reproducing information from a perpendicular magnetic recording medium that is recorded with servo information, eccentricity correction data and read/write data, by a reproducing head; filtering a reproduced output of the reproducing head, by filtering the servo information which has a differentiated waveform by a non-differentiating filter characteristic, and by filtering the eccentricity correction data and the read/write data which have rectangular waveforms by a differentiating filter characteristic; demodulating the servo information, the eccentricity correction data and the read/write data that are filtered by the filtering; outputting the demodulated servo information and eccentricity correction data to a servo system which carries out a control process including an eccentricity correction, and the demodulated read/write data to a data processing system; wherein the perpendicular magnetic recording medium has a servo region and a data region, the servo region is recorded with a first preamble, the servo information, a second preamble and the eccentricity correction data, and the data region is recorded with a third preamble and the read/write data, and generating first through third clocks and a servo mark from patterns of the first through third preambles having a constant period and mutually different frequencies, from the reproduced output of the reproducing head, wherein the filtering filters the reproduced output by the non-differentiating filter characteristic while reading the first preamble, the servo mark and address, and a servo burst within the servo region, based on the first clock and the servo mark, and filters the reproduced output by the differentiating filter characteristic while reading the second preamble and the eccentricity correction data within the servo region and the third preamble and the read/write data within the data region, based on the second clock and the servo mark.