Browse Prior Art Database

Laser Alignment Sensor for Disk Drive Assembly

IP.com Disclosure Number: IPCOM000101135D
Original Publication Date: 1990-Jul-01
Included in the Prior Art Database: 2005-Mar-16
Document File: 4 page(s) / 94K

Publishing Venue

IBM

Related People

Pack, TJ: AUTHOR [+2]

Abstract

This article describes a laser-based alignment sensor for placement of magnetic storage disks. The concept involves tracking a laser beam reflected by a retroreflector on the disk hub shaft. The center of rotation of the shaft is found and the disk is placed and aligned on the hub.

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

Laser Alignment Sensor for Disk Drive Assembly

       This article describes a laser-based alignment sensor for
placement of magnetic storage disks.  The concept involves tracking a
laser beam reflected by a retroreflector on the disk hub shaft.  The
center of rotation of the shaft is found and the disk is placed and
aligned on the hub.

      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 vision system which locates the center of the hub shaft.  Since
the system must stack up to nine disks individually, the sensor
system must be able to detect the hub shaft center over a depth of
field equal to the stack height (Fig. 1).

      Since conventional optical systems have very small depth of
field with respect to the stack height, the system must be refocused
or moved to maintain an image of the top of the hub shaft.  This
motion will introduce error in the measurement of the hub shaft
location.

      A laser-based sensor is disclosed herein which locates the
center of the hub shaft for accurate disk placement by the robot
EOAT.  The collimated nature of laser light and the use of a
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.

      The laser sensor of this disclosure is shown in Fig. 2. The
laser beam 1 is mounted...