Browse Prior Art Database

Servo Scheme for Patterned Media Using Optical Detection Integrated with the Head Structure

IP.com Disclosure Number: IPCOM000100483D
Original Publication Date: 1990-Apr-01
Included in the Prior Art Database: 2005-Mar-15
Document File: 3 page(s) / 133K

Publishing Venue

IBM

Related People

Lambert, SE: AUTHOR [+2]

Abstract

Disclosed is the application of optical servo techniques to magnetic recording on patterned media by integrating optics into the slider. Provision is made to precisely align the optical components with conventional heads used to read/write data.

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This is the abbreviated version, containing approximately 52% of the total text.

Servo Scheme for Patterned Media Using Optical Detection Integrated with the Head Structure

       Disclosed is the application of optical servo techniques
to magnetic recording on patterned media by integrating optics into
the slider.  Provision is made to precisely align the optical
components with conventional heads used to read/write data.

      Patterned media formed by etching discrete tracks on the
surface of rigid disks have been investigated recently for
conventional magnetic recording (1).  One potential advantage of this
technology is the possibility of achieving high track density by
using the patterned tracks as a source of servo information.  Many
schemes have been proposed for this including capacitance sensing and
various servo-on-data schemes, such as center-tapped magnetoresistive
heads.  It is obvious that optical detection of the patterned tracks
is also possible in analogy to optical disks.  In fact, there have
been proposals to eliminate a bulky focusing mechanism for optical
disks by placing the optics on a slider supported by an airbearing
using either on-slider optics [2,3] or optical fibers to connect to
optical components on the arm [4].  One difficulty with applying
these proposals to discrete tracks in conventional recording is
aligning the optical detectors with the read/write heads.  We propose
here a scheme which facilitates that alignment.

      The invention consists of using lithographically defined
optical waveguides to couple light from a light source to the
patterned surface of a magnetic disk.  The light that is
backscattered from the disk reenters the waveguide and a portion of
it is directed to one or more optical detectors.  The waveguides
could be fabricated on the same substrate as the thin film magnetic
head using an additional lithographic mask step.  The accuracy of
alignment of read/write heads with the optical servo detector will be
determined by the limitations of mask alignment.

      One possible implementation of the invention is shown in the
figure.  Light from a semiconductor laser or light-emitting diode is
coupled into a waveguide, which might consist of aluminum oxide or
other high refractive index dielectric.  The light is carried by the
waveguide to the air bearing surface of the slider.  The light exits
the waveguide and illuminates a small portion of the patterned media.
 Since the air bearing surface of the slider is only a fraction of a
wavelength above the disk surface, negligible diffraction occurs and
the width of the illuminated area is determined by the waveguide
geometry. The size of the illuminated region can be as small as
several microns.  The lateral displacement of the waveguide from the
read/write head is controlled by mask alignment and, in this case, is
an integral multiple of the track pitch.

      The light...