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

• US 9,123,370 B1
• Filed: 12/19/2014
• Issued: 09/01/2015
• 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:
  US14/578,054
• Time in Patent Office: 256 Days
• Field of Search: None
• US Class Current: 1/1
• CPC Class Codes: G11B 13/04 magnetically or by magnetisation and optically or by radiation, for changing or sensing optical properties
• 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, and a fly height actuator (FHA) configured to actuate the head vertically over the disk based on an FHA setting. 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. A FHA write setting is generated based on a calibrated write laser power, the first and second fly height measurements, and a first function representing a nominal FHA delta setting between a read touchdown FHA setting and a write touchdown FHA setting relative to a delta in a fly height of the head due to a corresponding change in laser power applied to the laser, 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, the first and second fly height measurements, and a first function representing a nominal FHA delta setting between a read touchdown FHA setting and a write touchdown FHA setting relative to a delta in a fly height of the head due to a corresponding change in laser power applied to the laser, 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 first function comprises a second order polynomial.

3. The data storage device as recited in claim 1, wherein the control circuitry is further configured to:

generate a second function representing the delta in fly height of the head relative to the laser power applied to the laser; and

generate the FHA write setting based on the second function.

4. The data storage device as recited in claim 3, wherein the second function comprises a linear function.

5. The data storage device as recited in claim 3, wherein the control circuitry is further configured to:

compute a calibrated delta in the fly height with the calibrated write laser power as an input to the second function; and

compute the FHA write setting with the calibrated delta in the fly height as an input to the first function.

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

calibrating a write laser power applied to a laser of a head during a write operation;

measuring a first fly height of the head over a disk 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, the first and second fly height measurements, and a first function representing a nominal FHA delta setting between a read touchdown FHA setting and a write touchdown FHA setting relative to a delta in a fly height of the head due to a corresponding change in laser power applied to the laser, where the FHA write setting is applied to the FHA during the write operation.

7. The method as recited in claim 6, wherein the first function comprises a second order polynomial.

8. The method as recited in claim 6, further comprising:

generating a second function representing the delta in fly height of the head relative to the laser power applied to the laser; and

generating the FHA write setting based on the second function.

9. The method as recited in claim 8, wherein the second function comprises a linear function.

10. The method as recited in claim 8, further comprising:

computing a calibrated delta in the fly height with the calibrated write laser power as an input to the second function; and

computing the FHA write setting with the calibrated delta in the fly height as an input to the first function.