Browse Prior Art Database

Flying-Height Measurement Using Fiber-Optic Interferometry

IP.com Disclosure Number: IPCOM000102446D
Original Publication Date: 1990-Nov-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 2 page(s) / 73K

Publishing Venue

IBM

Related People

Spong, JK: AUTHOR

Abstract

Disclosed is a device that uses a fiber-optic interferometer to measure the flying height of magnetic tape over the read/write head with sub-nm resolution. The fiber-optic configuration uses no discrete optics, requires no specialized structures (such as transparent head or media), and does not need to be isolated from vibrations. It can therefore be installed in an actual commercial drive, and used to characterize the drive performance or to provide the servo signal for precise control of tape tension or velocity.

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Flying-Height Measurement Using Fiber-Optic Interferometry

       Disclosed is a device that uses a fiber-optic
interferometer to measure the flying height of magnetic tape over the
read/write head with sub-nm resolution.  The fiber-optic
configuration uses no discrete optics, requires no specialized
structures (such as transparent head or media), and does not need to
be isolated from vibrations.  It can therefore be installed in an
actual commercial drive, and used to characterize the drive
performance or to provide the servo signal for precise control of
tape tension or velocity.

      The fiber-optic interferometer, shown schematically in the
figure, is based on a device used to measure small deflections of a
cantilever in the atomic force microscope (*).  The coherent light is
generated by a laser diode, operating at 830 nm, which couples the
light from the chip directly into a single-mode optical fiber.  The
entire unit is about 2x1x1 cm.  The output face of the optical fiber
is placed in the recording head, and light which exits the fiber is
reflected by the magnetic tape.  The interferometric cavity therefore
is formed by the output face of the fiber and the tape, as shown in
the figure.  The maximum signal is obtained with the fiber 5 to 10 mm
from the tape surface.  Since the fiber is rigidly mounted in the
head, no vibration isolation is needed.  The reflected and
transmitted signals from the interferometer are separated in a
fiber-optic decoupl...