Browse Prior Art Database

Simple and Inexpensive Device for Measuring Carbon Wear on Thin Film Disks

IP.com Disclosure Number: IPCOM000104573D
Original Publication Date: 1993-May-01
Included in the Prior Art Database: 2005-Mar-19
Document File: 2 page(s) / 84K

Publishing Venue

IBM

Related People

Meeks, SW: AUTHOR [+2]

Abstract

Disclosed is a design configuration and procedure for measuring the changes occurring on a magnetic recording disk surface during testing, such as the onset of disk damage and wear, using a relatively simple and inexpensive integrated optical device. The proposed configuration uses one or more integrated optical reflective sensors which consist of a light emitting diode, a photodetector and a bifurcated lens. These sensors (a commercially available example would be the HEDS-1200 or HEDS-1300 optical sensors which are manufactured by Hewlett Packard Co.) are positioned perpendicular to the surface of a thin film magnetic recording disk, as shown in section (a) of the figure. One particular embodiment of this device would be to use two such sensors, namely a data and a reference sensor.

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

Simple and Inexpensive Device for Measuring Carbon Wear on Thin Film Disks

      Disclosed is a design configuration and procedure for measuring
the changes occurring on a magnetic recording disk surface during
testing, such as the onset of disk damage and wear, using a
relatively simple and inexpensive integrated optical device.  The
proposed configuration uses one or more integrated optical reflective
sensors which consist of a light emitting diode, a photodetector and
a bifurcated lens.  These sensors (a commercially available example
would be the HEDS-1200 or HEDS-1300 optical sensors which are
manufactured by Hewlett Packard Co.) are positioned perpendicular to
the surface of a thin film magnetic recording disk, as shown in
section (a) of the figure.  One particular embodiment of this device
would be to use two such sensors, namely a data and a reference
sensor.  The data sensor is positioned behind a rail of a thin film
slider and the reflected signal is monitored as a function of time.
The reference sensor is positioned near the slider, closer to the
disk inner or outer diameter.  The data and reference sensors are
nominally identical sensors that are operated with identical currents
and bias voltages.  The reference sensor produces a signal which is
subtracted from the data sensor response, which removes most of the
drift associated with a single sensor.  The result is a signal which
shows only the changes occurring on the disk surface due to the thin
film slider contacting the disk surface.  These changes may be due to
disk damage, carbon wear (increased reflectivity due to less
absorption) or changes in the amount or nature of the lubricant on
the disk surface.

      A side-view of this invention is shown in section (b) of the
figure.  The minimum spot size for the above mentioned HEDS-1200 and
HEDS-1300 optical sensors is 130 and 190 microns, respectively.  This
spot size is on the order of or smaller than a typical current slider
railwidth (about 150 - 300 microns).  To monitor or image the full
disk region flown over by a slider, one may scan this optical device
in section (a)...