Browse Prior Art Database

Flying Optical Fiber for Disk Testing

IP.com Disclosure Number: IPCOM000114126D
Original Publication Date: 1994-Nov-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 2 page(s) / 107K

Publishing Venue

IBM

Related People

Gudeman, CS: AUTHOR [+2]

Abstract

The disclosed invention provides a noncontact method for measuring the morphology of an entire disk surface with high resolution in a relatively short period of time. This invention is potentially useful for testing thin film disks for magnetic recording. The Figure shows schematically the invention. A single mode optical fiber is attached to the back of a slider that flys over the rotating disk surface. The laser light that exits from the end of the optical fiber reflects off the disk surface and a fraction of the reflected light reenters the optical fiber where it interferes with light internally reflected off the end of the optical fiber.

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Flying Optical Fiber for Disk Testing

      The disclosed invention provides a noncontact method for
measuring the morphology of an entire disk surface with high
resolution in a relatively short period of time.  This invention is
potentially useful for testing thin film disks for magnetic
recording.  The Figure shows schematically the invention.  A single
mode optical fiber is attached to the back of a slider that flys over
the rotating disk surface.  The laser light that exits from the end
of the optical fiber reflects off the disk surface and a fraction of
the reflected light reenters the optical fiber where it interferes
with light internally reflected off the end of the optical fiber.

      Attaching the optical fiber on a flying slider provides a
mechanical feedback system so that the end of the fiber maintains a
fairly constant flying height over the disk surface.  By varying the
voltage applied to the piezoelectric material on the back of a
programmable air bearing slider, (1), the fly height can be adjusted
so that the interference cavity length is at the most sensitive part
of the interference fringe for measuring vertical variations in disk
morphology.  The fly height can also be adjusted by varying the load
on the slider or the rotation speed of the disk.  The fiber
interferometer is most sensitive to changes in morphology with
lateral dimensions less than and equal to the length of the slider
while much less sensitive to changes with lateral dimensions greater
than the slider length such as from disk curvature or run out or to
lateral dimensions smaller than laser spot size on the disk surface.
Using a single mode optical fiber provides for a very small laser
spot size.  For example, a single mode fiber for &lambda.  = 633 nm
the laser light is confined to a 4 &mu.m diameter optical core.  As
the light diverges from the end of the optical fiber, the end of the
fiber should be held close to the disk sur...