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