Browse Prior Art Database

Hybrid In-Situ Detection and Classification System for Protruding Surface Defects in DASD

IP.com Disclosure Number: IPCOM000123246D
Original Publication Date: 1998-Jul-01
Included in the Prior Art Database: 2005-Apr-04
Document File: 4 page(s) / 203K

Publishing Venue

IBM

Related People

Ottesen, HH: AUTHOR [+2]

Abstract

A detection/classification system of defects on surfaces of disks in a Direct Access Storage Device (DASD) is described. The magneto-restrictive (MR) read heads, used in the DASD, have independent magnetic and thermal response to a surface defect. This disclosure takes advantage of simultaneously employing the abrupt nature of the magnetic signal and thermal signal response of the MR head to a disk surface defect. The system responds to a large variation in the magnetic readback signal envelope, and simultaneously classifies the nature of the surface defect by observing the normalized local variance (NLV) of the thermal signal response. Based on the NLV the surface anomaly can be classified as bump or pit. Unlike disk surface pits, protruding surface bumps can be very damaging to DASD operation.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 93% of the total text.

Hybrid In-Situ Detection and Classification System for Protruding
Surface Defects in DASD

   A detection/classification system of defects on surfaces
of disks in a Direct Access Storage Device (DASD) is described.  The
magneto-restrictive (MR) read heads, used in the DASD, have
independent magnetic and thermal response to a surface defect.  This
disclosure takes advantage of simultaneously employing the abrupt
nature of the magnetic signal and thermal signal response of the MR
head to a disk surface defect.  The system responds to a large
variation in the magnetic readback signal envelope, and
simultaneously classifies the nature of the surface defect by
observing the normalized local variance (NLV) of the thermal signal
response.  Based on the NLV the surface anomaly can be classified as
bump or pit.  Unlike disk surface pits, protruding surface bumps can
be very damaging to DASD operation.  The system can be used for a
final test in DASD manufacturing and/or as an in-situ test for
accidental DASD surface damage in computers.

   Detailed Description of Detection/Classification System

   The difference in the normalized local variance (NLV) in
thermal signal levels of the MR head responding to surface bumps or
pits is significant.  Surface bumps exhibit very large NLV, while
pits have small NLV.  This difference in NLV is exploited in this
disclosure.  Pits are not damaging to the operation of disk drives
and can be considered as noise.  The protruding surfac...