Data storage device calibrating fly height actuator based on laser power for heat assisted magnetic recording

• US 8,976,633 B1
• Filed: 04/15/2014
• Issued: 03/10/2015
• Est. Priority Date: 04/15/2014
• 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: Ruan, Huanxiang, Chia, Galvin T.
• Primary Examiner(s): TRAN, THANG V
• Application Number:
  US14/253,491
• Time in Patent Office: 329 Days
• Field of Search: None
• US Class Current: 369/13.11
• 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 5/5534 Initialisation, calibration, e.g. cylinder "set-up"
• CPC Class Codes: G11B 5/6029 Measurement using values derived from the data signal read from the disk
• CPC Class Codes: G11B 5/607 using thermal means
• CPC Class Codes: G11B 5/6076 Detecting head-disk contact

Abstract

A data storage device is disclosed comprising a disk, a head comprising a laser configured to heat the disk while writing data to the disk, and a fly height actuator (FHA) configured to actuate the head vertically over the disk based on an FHA setting. A write laser power applied to the laser during a write operation is calibrated, a first fly height of the head is measured at a first laser power setting, and a second fly height of the head is measured at a second laser power setting different from the first laser power setting. A FHA write setting is generated based on the calibrated write laser power and the first and second fly height measurements, where the FHA write setting is applied to the FHA during the write operation.

Claims

1. A data storage device comprising:

a disk;

a head comprising a laser configured to heat the disk while writing data to the disk;

a fly height actuator (FHA) configured to actuate the head vertically over the disk based on an FHA setting; and

control circuitry configured to;

calibrate a write laser power applied to the laser during a write operation;

measure a first fly height of the head at a first laser power setting;

measure a second fly height of the head at a second laser power setting different from the first laser power setting; and

generate a FHA write setting based on the calibrated write laser power and the first and second fly height measurements, where the FHA write setting is applied to the FHA during the write operation.

2. The data storage device as recited in claim 1, wherein the control circuitry is further configured to measure the first and second fly height at a first FHA setting.

3. The data storage device as recited in claim 2, wherein the first FHA setting corresponds to an FHA read setting used to read data from the disk.

4. The data storage device as recited in claim 3, wherein the control circuitry is further configured to calibrate the FHA read setting based on a FHA touchdown setting that causes the head to contact the disk.

5. The data storage device as recited in claim 1, wherein the first laser power setting is substantially zero.

6. The data storage device as recited in claim 1, wherein the head does not contact the disk at the second laser power setting.

7. The data storage device as recited in claim 1, wherein the control circuitry is further configured to measure the second fly height of the head while applying a write current to the head.

8. The data storage device as recited in claim 1, wherein the control circuitry is further configured to generate the FHA write setting based on a difference between the first measured fly height and the second measured fly height.

9. The data storage device as recited in claim 8, wherein the control circuitry is further configured to generate the FHA write setting based on a function of the calibrated write laser power, wherein the function is based on the difference between the first measured fly height and the second measured fly height.

10. The data storage device as recited in claim 8, wherein the control circuitry is further configured to:

select one of a plurality of functions based on the difference between the first measured fly height and the second measured fly height; and

generate the FHA write setting based on the selected function.

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

calibrating a write laser power applied to a laser to heat a disk during a write operation;

measuring a first fly height of a head at a first laser power setting;

measuring a second fly height of the head at a second laser power setting different from the first laser power setting; and

generating a fly height actuator (FHA) write setting based on the calibrated write laser power and the first and second fly height measurements, where the FHA write setting is applied to a FHA to actuate the head vertically over the disk during the write operation.

12. The method as recited in claim 11, further comprising measuring the first and second fly height at a first FHA setting.

13. The method as recited in claim 12, wherein the first FHA setting corresponds to an FHA read setting used to read data from the disk.

14. The method as recited in claim 13, further comprising calibrating the FHA read setting based on a FHA touchdown setting that causes the head to contact the disk.

15. The method as recited in claim 11, wherein the first laser power setting is substantially zero.

16. The method as recited in claim 11, wherein the head does not contact the disk at the second laser power setting.

17. The method as recited in claim 11, further comprising measuring the second fly height of the head while applying a write current to the head.

18. The method as recited in claim 11, further comprising generating the FHA write setting based on a difference between the first measured fly height and the second measured fly height.

19. The method as recited in claim 18, further comprising generating the FHA write setting based on a function of the calibrated write laser power, wherein the function is based on the difference between the first measured fly height and the second measured fly height.

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

selecting one of a plurality of functions based on the difference between the first measured fly height and the second measured fly height; and

generating the FHA write setting based on the selected function.