Patent ID: 7486467

Claim:
A method of writing new patterns on a rotating medium by use of a writing element while reading existing patterns by using a reading element different from the writing element in terms of radial position, the method comprising the steps of: writing a plurality of patterns on a first track of the rotating medium; while modulating a clock frequency by using a difference between readout time of each pattern on the first track and target time for the pattern on the first track, writing patterns on a second track after a previously calculated delay time from readout of the pattern of the first track that becomes a reference pattern; storing a timing error of the pattern on the first track into memory during pattern writing on the second track; and while correcting target time for the patterns on the second track by use of the timing error of the pattern on the first track and modulating the clock frequency by use of a difference between readout time of each pattern on the second track and the corrected target time for the pattern on the second track, writing patterns on a third track after a previously calculated delay time from readout of each pattern present on the second track.