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Method and Apparatus for Measuring Disk Curvature at the Merge Stage of Assembly of an HDA

IP.com Disclosure Number: IPCOM000112712D
Original Publication Date: 1994-Jun-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 2 page(s) / 58K

Publishing Venue

IBM

Related People

Lee, CK: AUTHOR [+2]

Abstract

Disclosed is a method for measuring disk curvature at the merge stage of assembly of an HDA. This technique is non-contact, simple and can scan single or multiple disk surfaces. The device works by reflecting a laser diode beam off a thin film disk surface at an angle near grazing. The beam is then split with a non-polarizing beam splitter, and each beam is then directed onto a lens. Subsequently each beam is then directed onto a 1-D position-sensitive detector located at the focal plane of the lens. The beam is translated over the disk and the resultant signal from the position-sensitive detector gives the required first derivatives needed for the curvature of the disk.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Method and Apparatus for Measuring Disk Curvature at the Merge Stage
of Assembly of an HDA

      Disclosed is a method for measuring disk curvature at the merge
stage of assembly of an HDA.  This technique is non-contact, simple
and can scan single or multiple disk surfaces.  The device works by
reflecting a laser diode beam off a thin film disk surface at an
angle near grazing.  The beam is then split with a non-polarizing
beam splitter, and each beam is then directed onto a lens.
Subsequently each beam is then directed onto a 1-D position-sensitive
detector located at the focal plane of the lens.  The beam is
translated over the disk and the resultant signal from the
position-sensitive detector gives the required first derivatives
needed for the curvature of the disk.

      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 beam is focussed with a 70
mm focal length lens to allow it to pass between the closely spaced
disks.  The angle of the laser beam with respect to the disk is
approximately 85 degrees.  After the beam reflects from the disk, it
is split into two equal intensity beams by a non-polarizing beam
splitter.  These beams then pass through an imaging lens and onto a
1-D position-sensitive detector, which is placed at the focal length
of the imaging lens.  This configuration allows one to measure the
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