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Browse Prior Art Database

Laser Tilt Sensor for Disk Drive Assembly

IP.com Disclosure Number: IPCOM000100810D
Original Publication Date: 1990-Jun-01
Included in the Prior Art Database: 2005-Mar-16
Document File: 4 page(s) / 108K

Publishing Venue

IBM

Related People

Pack, TJ: AUTHOR [+2]

Abstract

This article describes a laser-based tilt sensor for detecting the tilt of a shaft with respect to a given orientation utilizing the tracking of two laser beam images reflected by a retroreflector on the shaft.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Laser Tilt Sensor for Disk Drive Assembly

       This article describes a laser-based tilt sensor for
detecting the tilt of a shaft with respect to a given orientation
utilizing the tracking of two laser beam images reflected by a
retroreflector on the shaft.

      Magnetic disk storage devices consist of multiple disks which
are stacked concentrically on a hub shaft.  Robots are used to handle
the disks and perform the placement.  To improve placement accuracy,
end- of-arm tooling (EOAT) includes a precise translation stage
guided by a sensor system which locates the center of the hub shaft
at the top of the shaft.  However, if the hub shaft is tilted with
respect to the EOAT axis, placement error will occur, as illustrated
in Fig. 1.  Disclosed herein is a laser-based sensor which locates
the center of rotation and the tilt of the hub shaft for accurate
disk placement by the robot EOAT.  The collimated nature of laser
light and the use of a custom retroreflector eliminate the need to
move optical components to maintain the depth of field specification.
Image analysis is performed with a commercial charge-coupled device
(CCD) camera and image processing system.

      The laser sensor system of this disclosure is shown in Fig. 2.
The laser beam 1 is mounted in the robot EOAT along with an
attenuator/beam expander 2, beamsplitter 3, and camera 4.  The
expanded input laser beam 5 is directed at the hub shaft 6 such that
it completely fills the aperture of a retroreflector 7 placed on top
of the shaft.  The retroreflector is an optical corner cube with the
property of returning the output beam 8 parallel to the input beam 5
independently to small variations in position and orientation.  In
addition, the top surface of the retroreflector is partially coated
with a reflective material.  Therefore, part o...