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Browse Prior Art Database

Separation of the Interferometer Laser from the Object

IP.com Disclosure Number: IPCOM000118182D
Original Publication Date: 1996-Oct-01
Included in the Prior Art Database: 2005-Apr-01
Document File: 2 page(s) / 48K

Publishing Venue

IBM

Related People

Wagner, D: AUTHOR

Abstract

Disclosed is a laser interferometer in which the laser light source is situated outside the interferometer. Optical fibers guide the laser light to the measuring machine.

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This is the abbreviated version, containing approximately 84% of the total text.

Separation of the Interferometer Laser from the Object

      Disclosed is a laser interferometer in which the laser light
source is situated outside the interferometer.  Optical fibers guide
the laser light to the measuring machine.

      Lasers with high power loss rates of about 50 W cause
temperature fluctuations in the air which have significant impact on
the measuring accuracy of the laser interferometers.  National
institutes for standards carry out their highly precise length
measurements in vacuum.  This is, however, not very cost effective
and, therefore, not  suitable for production areas like in the
semiconductor industry where  displacements in the nanometer range
have to be measured with high accuracy in several lithography tools
like wafer steppers or mask alignment tools.

      The laser beam consists of two circularly polarized components
with a slight difference in their frequency.  As shown in Fig. 1, the
two beam components of laser 1 are transformed into two orthogonally
polarized beams by the lambda/4 plate 2.  Beamsplitter 3 separates
these partial beams and by lenses 4 the partial beams are fed into
the optical  fibers guiding them to the measuring machine 6.  The
output face of the  optical fibers is rigidly fixed to the measuring
machine.  In the measuring machine 6 a polarizing beam splitter 7 and
lambda/4 plate 8 puts the partial beams together to a total beam
having the same properties as the original laser beam.

    ...