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Actuator Contact Free Servo Writer for DASD Using Phase Demodulated LDV

IP.com Disclosure Number: IPCOM000121410D
Original Publication Date: 1991-Aug-01
Included in the Prior Art Database: 2005-Apr-03
Document File: 1 page(s) / 54K

Publishing Venue

IBM

Related People

Chiang, WW: AUTHOR [+2]

Abstract

This servo writing scheme eliminates the requirement of having any mechanical contact of the actuator by an external precision stage or position encoder to control the actuator position of the magnetic disk drive during the servo writing process. This method also does not require the attachment of any reflection device to the actuator to reflect the laser beam for position measurement. The slider position is measured directly by the laser which eliminates the error caused by the suspension vibration.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 78% of the total text.

Actuator Contact Free Servo Writer for DASD Using Phase Demodulated
LDV

      This servo writing scheme eliminates the requirement of having
any mechanical contact of the actuator by an external precision stage
or position encoder to control the actuator position of the magnetic
disk drive during the servo writing process.  This method also does
not require the attachment of any reflection device to the actuator
to reflect the laser beam for position measurement.  The slider
position is measured directly by the laser which eliminates the error
caused by the suspension vibration.

      As shown in the figure, a focused laser beam from a Laser
Doppler Vibrometer (LDV) is directed to the side of a slider to
measure its position and the actuator position is controlled by its
own Voice Coil Motor (VCM).  An optical opening at the side of the
base plate is required to allow the laser beam to pass through.  A
phase demodulator is used to demodulate the LDV optical signal to
track the absolute position of the slider with high accuracy.  Due to
the fact that the focused laser beam has a finite field of depth of
the focal point which is usually much smaller than the entire moving
range of the actuator inside the disk drive, a linear or rotary stage
is used to move the drive's base plate to achieve a large relative
motion between the actuator and the drive while maintaining the
slider within the laser beam's measurement volume.  A linear stage
will be used for drives wi...