Storage media asperity characterization

Patent metadata

Field	Value
Publication number	US-9335153-B2
Application number	US-201213627731-A
Country	US
Kind code	B2
Filing date	Sep 26, 2012
Priority date	Sep 26, 2012
Publication date	May 10, 2016
Grant date	May 10, 2016

Abstract

The present application discloses detecting an asperity on a storage media surface using two amplitude threshold crossings of an asperity detection signal within a preset timing window. The present application further discloses a temperature-dependent resistive asperity sensor and a preamplifier that correlates a resistance change at the asperity sensor within a preset timing window to detect an asperity on a storage media surface. The asperity may be one or both of a void in the storage media surface and a protrusion from the storage media surface.

First claim

What is claimed is:

1. A method comprising:
selecting for detection one of protruding and recessed asperities on a storage media surface;
detecting an initial amplitude threshold crossing of a detection signal;
starting a timing window at the initial amplitude threshold crossing;
detecting a subsequent amplitude threshold crossing within the timing window; and
detecting a selected asperity on the storage media surface based on the initial amplitude threshold crossing and the subsequent amplitude threshold crossing.

2. The method of claim 1 , further comprising disabling one or more transducer head heaters when moving a transducer head over a protruding asperity on the storage media surface.

3. The method of claim 1 , wherein the asperity detection signal is a voltage over time signal and the amplitude threshold crossings are voltages.

4. The method of claim 1 , further comprising disabling one or more transducer head heaters when moving a transducer head over an area adjacent to a protruding asperity on the storage media surface.

5. The method of claim 1 , wherein the timing window is started at a first in time detected amplitude threshold crossing that is increasing in magnitude and has a polarity corresponding to the selecting operation.

6. The method of claim 1 , wherein the initial amplitude threshold crossing is increasing in magnitude and the subsequent amplitude threshold crossing is decreasing in magnitude.

7. The method of claim 1 , wherein the detecting operation includes ignoring threshold crossings subsequent to the initial and subsequent amplitude threshold crossings within the preset timing window.

8. The method of claim 1 , further comprising:
outputting one or more fault codes associated with the detected asperity, wherein a quantity of the fault codes corresponds to a length of the detected asperity.

9. The method of claim 1 , wherein the detection signal corresponds to a resistance change across an asperity sensor.

10. The method of claim 9 , wherein the resistance change across the asperity sensor is a result of a temperature change at the asperity sensor.

11. The method of claim 9 , wherein the asperity sensor is located on a transducer head and operates independently of a read element on the transducer head.

12. An asperity detection system comprising:
a temperature-dependent resistive asperity sensor; and
a preamplifier that selects for detection one of protruding and recessed asperities on a storage media surface, detects an initial threshold crossing of a detection signal, starts a timing window at the initial threshold crossing, detects a subsequent threshold crossing within the timing window, and detects a selected asperity on the storage media surface based on the initial threshold crossing and the subsequent threshold crossing within the timing window defined by a partial pass of a selected track of the storage media surface.

13. The asperity detection system of claim 12 , wherein the preamplifier disables one or more transducer head heaters when moving over a detected protruding asperity on the storage media surface.

14. The asperity detection system of claim 12 , wherein the preamplifier receives a resistance change at the temperature-dependent resistive asperity sensor as an asperity detection signal.

15. The asperity detection system of claim 12 , wherein the preamplifier further comprises:
a sensor bias to apply a bias voltage across the asperity sensor and a sensor driver to receive a biased voltage change and output an amplitude varied voltage corresponding to the resistance change.

16. The asperity detection system of claim 15 , wherein the preamplifier further comprises:
a comparator to receive the amplitude varied voltage and perform a comparison to determine if one or more thresholds are exceeded to detect the asperity.

17. The asperity detection system of claim 12 , wherein the asperity sensor is located on a transducer head and operates independently of a read element on the transducer head.

18. A method comprising:
passing a transducer head over a storage media surface;
selecting for detection one of protruding and recessed asperities on the storage media surface; and
detecting a selected asperity on the storage media surface using a temperature change at an asperity sensor on the transducer head, the temperature change occurring within a preset timing window defined by a partial pass of a selected track on the storage media surface; and
disabling one or more transducer head heaters when moving the transducer head over a detected protruding asperity on the storage media surface.

19. The method of claim 18 , wherein the detecting operation is performed using two amplitude threshold crossings of an asperity detection signal received from the asperity sensor.

20. The method of claim 18 , further comprising disabling one or more transducer head heaters when moving the transducer head over an area adjacent to the detected protruding asperity on the storage media surface.

Assignees

• Seagate Technology Llc

Inventors

• Matousek Robert
• Powers Kevin David
• Riley Dale Thomas

Classifications

• G01B7/34 Primary

  for measuring roughness or irregularity of surfaces · CPC title

• G11B5/607

  using thermal means · CPC title

• G11B27/36 Primary

  Monitoring, i.e. supervising the progress of recording or reproducing {(for digital recording G11B20/00 and s.gr.; for monitoring, testing or measuring of TV recorders of the type covered by H04N5/76 and subgroups, see H04N17/06)} · CPC title

• G11B5/6076

  Detecting head-disk contact · CPC title