Browse Prior Art Database

Disk Handling Damage Detector

IP.com Disclosure Number: IPCOM000113232D
Original Publication Date: 1994-Jul-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 2 page(s) / 44K

Publishing Venue

IBM

Related People

Meeks, SW: AUTHOR [+2]

Abstract

Disclosed is a device to measure disk handling damage at the pre-sputter stage of the production of a thin film disk. This device consists of a collimated and stabilized laser diode which is focused with a 100 cm focal length lens and scanned over a disk surface with a single axis optical scanner (e.g., galvanometer or rotating polygon). The reflected and scanned beam is received with an extended detector to allow receipt of the scanned beam. This extended detector allows the measurement of light intensity. A defect on the disk will scatter light out of the beam and the resulting intensity measured with the detector will be reduced. In this manner this device can measure disk dings, gouges, dents, scratches, and defects as small as 10 microns in size.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 68% of the total text.

Disk Handling Damage Detector

      Disclosed is a device to measure disk handling damage at the
pre-sputter stage of the production of a thin film disk.  This device
consists of a collimated and stabilized laser diode which is focused
with a 100 cm focal length lens and scanned over a disk surface with
a single axis optical scanner (e.g., galvanometer or rotating
polygon).  The reflected and scanned beam is received with an
extended detector to allow receipt of the scanned beam.  This
extended detector allows the measurement of light intensity.  A
defect on the disk will scatter light out of the beam and the
resulting intensity measured with the detector will be reduced.  In
this manner this device can measure disk dings, gouges, dents,
scratches, and defects as small as 10 microns in size.

      The extended detector used in this invention is modified so
that the intensity of the laser beam is independent of the position
that the laser beam strikes the detector.  This makes the use of a
scanner feasible and reduces the effects of environmental vibration.
This device uses a low power collimated laser diode at 780 or 670 nm
which is reflected at an angle near grazing from the thin film disk
surface.  The laser is S polarized since the disk is more reflective
for S polarization.  The laser has been stabilized with a beam
splitter and a reference photodiode.  The split beam is fed back to
the laser current control and the resulting feedback loop controls
the...