Browse Prior Art Database

Low-Cost Actuator Positioner For Servo Writing DASD

IP.com Disclosure Number: IPCOM000104822D
Original Publication Date: 1993-Jun-01
Included in the Prior Art Database: 2005-Mar-19
Document File: 2 page(s) / 65K

Publishing Venue

IBM

Related People

Dang, HP: AUTHOR [+2]

Abstract

Disclosed is an inexpensive way to provide a high-resolution positioning reference needed in servo writing Direct-Access Storage Devices (DASD).

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

Low-Cost Actuator Positioner For Servo Writing DASD

      Disclosed is an inexpensive way to provide a high-resolution
positioning reference needed in servo writing Direct-Access Storage
Devices (DASD).

      Most Servowriters for mid- to high-capacity DASD use a Laser
Interferometer as the positioning reference.  This provides in the
order of  0.4 microinches positioning accuracy over the the full
stroke of the actuator arm.  This laser system is still very
expensive and that drives up the overall cost of the servowriter.  A
method was proposed to use the spacing between pits (or bubbles) on
the Write-Once-Read-Many (WORM) optical disk as the positioning
reference.  An existing WORM writer deposits pits with 1.6 micrometer
spacing.

      As shown in the figure, the master arm is positioned by the
master controller in 1.6 micrometer steps, using feedback signal,
v sub o
, from the optical head electronics.  The master controller uses the
slope of
v sub o
to keep the master arm in position.  By varying the size of the pits
with respect to the active area of the photodetector, one can control
the slope of
v sub o
It is easier for the master controller to follow shallow-slope
v sub o
, but the position accuracy is not as good as that of a steep-slope
signal.  Optical components found in the consumer compact disk (CD)
player can be used without modification; only some of the electronics
have to be changed.  Unlike a consumer CD player, the optical disk
stays stationary and the o...