Delay clock track read back data to compensate time variance due to disk thermal expansion in spiral servo track writing

A servo writer that writes servo information onto a disk of a hard disk drive that has a head, comprising:

• a clock head that reads a clock track of the disk;
• a circumferential index detector coupled to said clock head;
• a radial index detector coupled to the head of the hard disk drive;
• a phase detector coupled to said circumferential index detector and said radial index detector;
• a delay line circuit coupled to said phase detector, said clock head and said circumferential index detector;
• and,
• a controller coupled to said radial index detector and said circumferential index detector.

A servo writer that writes servo information onto a disk of a hard disk drive that has a head that generates a reference signal, comprising:

• a clock head that reads a clock track of the disk and generates a clock signal;
• circumferential index detector means for detecting a circumferential index from said clock signal;
• radial index means for detecting a radial index from the reference signal;
• phase detector means for determining a phase difference between the circumferential index and the radial index;
• delay means for delaying the clock signal provided to said circumferential detector means as a function of said phase difference;
• and,
• controller means for writing a servo pattern onto the disk in response to detection of said circumferential index and said radial index.

A circuit of a servo writer that writes servo information onto a disk of a hard disk drive that has a head, the servo writer including a clock head, comprising:

• a circumferential index detector coupled to the clock head;
• a radial index detector coupled to the head of the hard disk drive;
• a phase detector coupled to said circumferential index detector and said radial index detector;
• and,
• a delay line circuit coupled to said phase detector, the clock head and the circumferential index detector.

A circuit for a servo writer that writes servo information onto a disk of a hard disk drive that has a head that generates a reference signal, the servo writer has a clock that generates a clock signal comprising:

• circumferential index detector means for detecting a circumferential index from the clock signal;
• radial index means for detecting a radial index from the reference signal;
• phase detector means for determining a phase difference between the circumferential index and the radial index;
• and,
• delay means for delaying the clock signal provided to said circumferential detector means as a function of said phase difference.