Browse Prior Art Database

Miniature Differential Laser Interferometer/Vibrometer for Optical Glide and Other Storage Applications

IP.com Disclosure Number: IPCOM000112413D
Original Publication Date: 1994-May-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 4 page(s) / 113K

Publishing Venue

IBM

Related People

Chiang, WW: AUTHOR [+6]

Abstract

Disclosed is an optical/electronic configuration of laser Doppler interferometer/vibrometer that can be easily miniaturized.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 47% of the total text.

Miniature Differential Laser Interferometer/Vibrometer for Optical
Glide and Other Storage Applications

      Disclosed is an optical/electronic configuration of laser
Doppler interferometer/vibrometer that can be easily miniaturized.

      The disclosed device provides us with an opportunity to achieve
advantages similar to that of the PZT (lead-zirconate-titanate)
specialty head, a direct storage access device industry manufacturing
standard for disk glide, while avoiding the high cost associated with
using the specialty heads.  Due to the high bandwidth and large
dynamic range inherited in the laser Doppler
interferometer/vibrometer configuration disclosed herein, both the
low frequency glide specifications (which related to air-bearing) and
the high frequency specifications (which related to slider modal
vibration excited by disk asperities) can be measured on regular
heads.  The potential cost saving by adopting this optical
configuration on the disk production process is significant.  In
addition, the newly disclosed device have the potential to allow us
to easily combine the burnish and glide steps.  Furthermore, the
disclosed device can also be used as a stand alone laser Doppler
vibrometer and a laser interferometer.

      The schematic of the disclosed device is shown in the Figure.
The laser light emitted from the laser (which can be a laser diode or
a gas laser, etc.) is first collimated and aligned so that a linearly
polarized light beam is propagated along the rotational axis of the
rotating laser mount.  This collimated laser light is then split by a
polarizing beam splitter (PBS1) into two object beams, E sub o1  and
E sub o2 .  The relative return intensity ratio of the two object
beams can be adjusted by rotating the laser optical axis relative to
the beam splitting plane of the PBS1.  This adjustment ensures that
the optical intensity of the two return object beams is identical in
order to minimize the background noise.  One of the main reasons that
this optical configuration can be easily miniaturized is that the
Bragg Cell typically used for removing the directional ambiguity in a
standard Doppler vibrometer configuration has been removed.  The
off-axis performance of these two focusing lens,
L sub 1  and  L sub 2 , is utilized, i.e. the outgoing object beams
and the returning object beams are incident on different locations of
the focusing lens.  An aperture mirror is adopted to separate the
outgoing light beams and the returning light beams.  The focused beam
configuration allows this optical design to operate in the case that
the measurement object surface does not have a flatness less than say
1/4 wavelength within the light spot.  As both object beams remain
linearly polarized and orthogonal with respect to each other,
polarization beam splitters (PBS1 and PBS2) can be used to separate
these two beams.  The two object beams remain linearly polarized and
are orthogonal with respect to ea...