Data storage device calibrating a laser power for heat assisted magnetic recording based on slope of quality metric

• US 9,384,774 B1
• Filed: 03/23/2015
• Issued: 07/05/2016
• Est. Priority Date: 03/23/2015
• Status: Active Grant

• Current Assignee: JP Morgan Chase Bank, N.A. (JP Morgan Chase & Co)
• Original Assignee: Western Digital Technologies Incorporated (Western Digital Corporation)
• Inventors: Nookala, Poornima, Haralson, Phillip Scott
• Primary Examiner(s): Pendleton, Dionne H
• Application Number:
  US14/666,080
• Time in Patent Office: 470 Days
• Field of Search: 360/77.08, 360/77.02, 360/66, 360/62, 360/55, 369/13.04, 369/13.05, 369/13.1, 369/13.16, 369 1324- 1327, 369 475- 4755, 369/53.2, 369/59.1, 369/124.1
• US Class Current: 1/1
• CPC Class Codes: G11B 20/10009 Improvement or modification of read or write signals
• CPC Class Codes: G11B 20/10305 signal quality assessment
• CPC Class Codes: G11B 20/10472 derived from statistics of other quality measures, e.g. their mean, variance or skew
• CPC Class Codes: G11B 20/10481 optimisation methods
• CPC Class Codes: G11B 2005/0021 Thermally assisted recording using an auxiliary energy source for heating the recording layer locally to assist the magnetization reversal
• CPC Class Codes: G11B 5/02 Recording, reproducing, or erasing methods; Read, write or erase circuits therefor
• CPC Class Codes: G11B 5/455 Arrangements for functional testing of heads; Measuring arrangements for heads
• CPC Class Codes: G11B 5/5534 Initialisation, calibration, e.g. cylinder "set-up"
• CPC Class Codes: G11B 7/00736 Auxiliary data, e.g. lead-in, lead-out, Power Calibration Area [PCA], Burst Cutting Area [BCA], control information sector headers or adresses in prepits G11B7/00745; address data in track wobble G11B7/24082
• CPC Class Codes: G11B 7/1263 Power control during transducing, e.g. by monitoring
• CPC Class Codes: G11B 7/1267 Power calibration

Abstract

A data storage device is disclosed comprising a disk and a head actuated over the disk, wherein the head comprises a laser configured to heat the disk while writing data to the disk. The laser power is adjusted and a pattern is written to a target track at the adjusted laser power. The pattern is read from the target track to generate a read signal, and a quality metric is generated based on the read signal. The process is repeated at least once, and a write power for the laser is configured based on a slope of the quality metric.

Claims

1. A data storage device comprising:

a disk;

a head actuated over the disk, the head comprising a laser configured to heat the disk while writing data to the disk; and

control circuitry configured to;

(a) adjust a laser power for the laser;

(b) write a pattern to a target track at the adjusted laser power;

(c) read the pattern from the target track to generate a read signal;

(d) amplify the read signal using a variable gain amplifier

(e) generate a quality metric based on a setting for the variable gain amplifier;

(f) repeat blocks (a) through (e) at least once; and

(g) configure a write power for the laser based on a slope of the quality metric.

2. The data storage device as recited in claim 1, wherein the control circuitry is further configured to configure a write power for the laser based on a change in the slope of the quality metric.

3. The data storage device as recited in claim 1, wherein the pattern consists of a periodic pattern.

4. The data storage device as recited in claim 1, wherein block (b) further comprises writing a pattern to at least one track adjacent the target track at the adjusted laser power.

5. A data storage device comprising:

a disk;

a head actuated over the disk, the head comprising a laser configured to heat the disk while writing data to the disk; and

control circuitry configured to;

(a) adjust a laser power for the laser;

(b) write a first pattern to a target track at the adjusted laser power;

(c) read the first pattern from the target track to generate a first read signal;

(d) generate a first quality metric based on the first read signal;

(e) write a second pattern to the target track at the adjusted laser power;

(f) read the second pattern from the target track to generate a second read signal;

(g) generate a second quality metric based on the second read signal;

(h) generate a third quality metric based on the first quality metric and the second quality metric;

(i) repeat blocks (a) through (h) at least once; and

(j) configure a write power for the laser based on a slope of the third quality metric.

6. The data storage device as recited in claim 5, wherein the control circuitry is further configured to configure a write power for the laser based on a change in the slope of the third quality metric.

7. The data storage device as recited in claim 5, wherein the first pattern consists of a DC pattern and the second pattern consists of a periodic pattern.

8. The data storage device as recited in claim 5, wherein the first pattern consists of a first periodic pattern having a first frequency and the second pattern consists of a second periodic pattern having a second frequency different from the first frequency.

9. The data storage device as recited in claim 5, wherein:

the first quality metric is generated based on a first setting for a variable gain amplifier; and

the second quality metric is generated based on a second setting for the variable gain amplifier.

10. The data storage device as recited in claim 9, wherein the control circuitry is further configured to generate the third quality metric based on a difference between the first quality metric and the second quality metric.

11. The data storage device as recited in claim 9, wherein the control circuitry is further configured to:

write the first pattern to a first part of the target track; and

write the second pattern to a second part of the target track.

12. The data storage device as recited in claim 11, wherein the control circuitry is further configured to write the first pattern and the second pattern to the target track during a first revolution of the disk.

13. The data storage device as recited in claim 12, wherein the control circuitry is further configured to read the first pattern and the second pattern from the target track during a second revolution of the disk.

14. A method of operating a data storage device, the method comprising:

(a) adjusting a laser power for a laser;

(b) writing a pattern to a target track on a disk at the adjusted laser power;

(c) reading the pattern from the target track to generate a read signal;

(d) amplifying the read signal using a variable gain amplifier;

(e) generating a quality metric based on a setting for the variable gain amplifier;

(f) repeating blocks (a) through (e) at least once; and

(g) configuring a write power for the laser based on a slope of the quality metric.

15. The method as recited in claim 14, further comprising configuring a write power for the laser based on a change in the slope of the quality metric.

16. The method as recited in claim 14, wherein the pattern consists of a periodic pattern.

17. The method as recited in claim 14, wherein block (b) further comprises writing a pattern to at least one track adjacent the target track at the adjusted laser power.

18. A method of operating a data storage device, the method comprising:

(a) adjusting a laser power for a laser;

(b) writing a first pattern to a target track on a disk at the adjusted laser power;

(c) reading the first pattern from the target track to generate a first read signal;

(d) generating a first quality metric based on the first read signal;

(e) writing a second pattern to the target track at the adjusted laser power;

(f) reading the second pattern from the target track to generate a second read signal;

(g) generating a second quality metric based on the second read signal;

(h) generating a third quality metric based on the first quality metric and the second quality metric;

(i) repeating blocks (a) through (h) at least once; and

(j) configuring a write power for the laser based on a slope of the third quality metric.

19. The method as recited in claim 18, further comprising configuring a write power for the laser based on a change in the slope of the third quality metric.

20. The method as recited in claim 18, wherein the first pattern consists of a DC pattern and the second pattern consists of a periodic pattern.

21. The method as recited in claim 18, wherein the first pattern consists of a first periodic pattern having a first frequency and the second pattern consists of a second periodic pattern having a second frequency different from the first frequency.

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

the first quality metric is generated based on a first setting for a variable gain amplifier; and

the second quality metric is generated based on a second setting for the variable gain amplifier.

23. The method as recited in claim 22, further comprising generating the third quality metric based on a difference between the first quality metric and the second quality metric.

24. The method as recited in claim 18, further comprising:

writing the first pattern to a first part of the target track; and

writing the second pattern to a second part of the target track.

25. The method as recited in claim 24, further comprising writing the first pattern and the second pattern to the target track during a first revolution of the disk.

26. The method as recited in claim 25, further comprising reading the first pattern and the second pattern from the target track during a second revolution of the disk.