Method for nonsequentially writing reference spiral servo patterns to a disk to compensate for disk expansion

1. A method for reducing disk expansion effects while writing spiral reference patterns on a disk of a disk drive, the disk drive comprising control circuitry and a head disk assembly (HDA) comprising the disk, an actuator arm, a head connected to a distal end of the actuator arm, and a voice coil motor for rotating the actuator arm about a pivot to position the head radially over the disk, the method comprising:

using an external spiral servo writer to control a radial location of the head for writing a plurality of the spiral reference patterns in an order such that at least two of the spiral reference patterns are not written temporally sequential to an adjacent spiral reference pattern; and

using the head internal to the disk drive to read the spiral reference patterns in order to write product servo bursts to the disk, thereby defining a plurality of radially spaced, concentric data tracks.

2. The method as recited in claim 1 , further comprising inserting a head positioning pin of the external spiral servo writer into the HDA before writing the spiral reference patterns, the head positioning pin for engaging the actuator arm.

3. The method as recited in claim 1 , wherein the spiral reference patterns are temporally written in a nonsequential order.

4. The method as recited in claim 1 , wherein the reference patterns are temporally written in a pseudorandom order.

5. The method as recited in claim 1 , wherein the plurality of spiral reference patterns comprise n spiral paths and the temporal order that the spiral paths are written follows the sequence: n, n−2, n−4, . . . , 4, 2, 1, 3, 5, . . . , n−3, n−1, where the temporal order number 1 is the first spiral path written and the temporal order number n is the last spiral path written.

6. The method as recited in claim 1 , wherein the plurality of spiral reference patterns comprise n spiral paths and the temporal order that the spiral paths are written follows the sequence: n, n−2, n−4, . . . , 5, 3, 1, 2, 4, . . . , n−3, n−1, where the temporal order number 1 is the first spiral path written and the temporal order number n is the last spiral path written.

7. The method as recited in claim 1 , wherein the plurality of spiral reference patterns comprise n spiral paths and the temporal order that the spiral paths are written follows the sequence: n−1, n−3, . . . , 4, 2, 1, 3, 5, . . . n−4, n−2, n, where the temporal order number 1 is the first spiral path written and the temporal order number n is the last spiral path written.

8. The method as recited in claim 1 , wherein the plurality of spiral reference patterns comprise n spiral paths and the temporal order that the spiral paths are written follows the sequence: n−1, n−3, . . . , 5, 3, 1, 2, 4, . . . n−4, n−2, n, where the temporal order number 1 is the first spiral path written and the temporal order number n is the last spiral path written.

9. The method as recited in claim 1 , wherein the control circuitry of the disk drive is used to process the spiral reference patterns in order to write the product servo bursts to the disk during a self-servo writing operation.

10. The method as recited in claim 1 , wherein an external product servo writer is used to process the spiral reference patterns in order to write the product servo bursts to the disk.

11. The method as recited in claim 1 , wherein the external spiral servo writer comprises a laser interferometer for deriving the radial location of the head.

12. The method as recited in claim 1 , wherein each spiral reference pattern is written from an outer diameter of the disk to an inner diameter of the disk.

13. The method as recited in claim 1 , wherein each spiral reference pattern is written from an inner diameter of the disk to an outer diameter of the disk.

14. The method as recited in claim 1 , wherein the spiral reference patterns are written alternately from an inner diameter of the disk to an outer diameter of the disk and from an outer diameter of the disk to an inner diameter of the disk.

15. The method as recited in claim 1 , wherein the product servo bursts are written in a substantially circular path.

16. The method as recited in claim 1 , wherein:

a radial length of a product servo burst defines a data track;

the product servo bursts form a plurality of servo wedges; and

a slope of each spiral reference pattern equals approximately one data track per servo wedge.

17. The method as recited in claim 16 , wherein the number of spiral reference patterns equals the number of servo wedges.

18. The method as recited in claim 1 , wherein:

the product servo bursts form a plurality of servo wedges; and

a slope of each spiral reference pattern equals approximately one radial length of a product servo burst per servo wedge.

19. The method as recited in claim 18 , wherein the number of spiral reference patterns equals the number of servo wedges.

20. The method as recited in claim 1 , wherein each spiral reference pattern is written over at least twenty revolutions of the disk.

21. The method as recited in claim 1 , wherein:

each spiral reference pattern comprises a plurality of reference servo bursts;

each reference servo burst comprises a plurality of high frequency transitions; and

the reference servo bursts are recorded at a periodic interval within each spiral reference pattern.

22. The method as recited in claim 21 , wherein the reference servo bursts are substantially contiguous in the radial direction from an outer diameter of the disk to an inner diameter of the disk.