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Method and Apparatus for Simultaneously Measuring Wear and Roughness on Thin Film Disks

IP.com Disclosure Number: IPCOM000111905D
Original Publication Date: 1994-Apr-01
Included in the Prior Art Database: 2005-Mar-26
Document File: 2 page(s) / 40K

Publishing Venue

IBM

Related People

Meeks, SW: AUTHOR [+2]

Abstract

Disclosed is a device for optically measuring changes occurring on a thin film disk surface. The device consists of an optical beam from a collimated laser diode, a portion of which passes through a beam splitter and into a reference photodiode for laser stabilization. The remainder of the beam continues through the beam splitter and is focussed at the thin film interface, which is located at an exit port of the integrating sphere where it is reflected and scattered by the thin film coating surface. The specular beam reflects from the substrate and exits the sphere, being measured with the specular light photodetector. The light scattered from the disk surface is collected or integrated by the hollow sphere and is detected with the additional scattered light photodiode at the top of the sphere.

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Method and Apparatus for Simultaneously Measuring Wear and Roughness
on Thin Film Disks

      Disclosed is a device for optically measuring changes occurring
on a thin film disk surface.  The device consists of an optical beam
from a collimated laser diode, a portion of which passes through a
beam splitter and into a reference photodiode for laser
stabilization.  The remainder of the beam continues through the beam
splitter and is focussed at the thin film interface, which is located
at an exit port of the integrating sphere where it is reflected and
scattered by the thin film coating surface.  The specular beam
reflects from the substrate and exits the sphere, being measured with
the specular light photodetector.  The light scattered from the disk
surface is collected or integrated by the hollow sphere and is
detected with the additional scattered light photodiode at the top of
the sphere.   The scattered light depends on the roughness of the
thin film surface.

      A liquid crystal variable 1/2 wave plate can automatically
change the laser beam polarization state from P to S polarization,
and further, for a given polarization light type, both the specular
and scattered light types can be simultaneously acquired.  This means
that during an interface test, four distinct optical images of the
disk surface can be obtained; namely P specular and P scattered as
well as S specular and S scattered images.  The P specular light is
used for measuring carbon wear a...