Patent ID: 7253985

Claim:
A method for writing servo information onto a disk of a hard disk drive, comprising: generating a clock signal from the disk with a clock head; detecting a first circumferential index signal from the clock signal; generating a reference signal from the disk with a disk drive head; detecting a first radial index signal from the reference signal; writing a first spiral servo track onto the disk in response to the detection of the first circumferential index signal and the first radial index signal; detecting a first phase difference between the first circumferential index signal and the first radial index signal; detecting a second circumferential index signal from the delayed clock read back signal; detecting a second radial index signal; synchronizing the detected second circumferential and second radial index signals with the first phase difference; and, writing a second spiral servo track onto the disk in response to the synchronized second circumferential and second radial index signals.