Browse Prior Art Database

Highly Accurate Rapid Incremental Interferometric Measurement of Rotary Motion

IP.com Disclosure Number: IPCOM000115452D
Original Publication Date: 1995-May-01
Included in the Prior Art Database: 2005-Mar-30
Document File: 2 page(s) / 80K

Publishing Venue

IBM

Related People

Wagner, D: AUTHOR

Abstract

Disclosed is an interferometer capable of measuring angles up to 90º and an integrated phase measuring system capable of analyzing interferences of this broad range. The interferometer reaches up to 10(7) pixels per scan with a maximum pixel frequency of more than 100 MHz.

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Highly Accurate Rapid Incremental Interferometric Measurement of
Rotary Motion

      Disclosed is an interferometer capable of measuring angles up
to 90º  and an integrated phase measuring system capable of
analyzing interferences of this broad range.  The interferometer
reaches up to 10(7)  pixels per scan with a maximum pixel frequency
of more than 100 MHz.

      All laser scanners have an image-forming system and a rotating
scanner.  The scanner may rotate continuously (polygon scanner),
sinusoidally (resonance scanner) or arbitrarily (vector scanner).
For producing pixels of the same size precision scanners need an
incremental gauge which may be a circular disk with a grid or a
linear grid with an additional image-forming system.  The incremental
gauges are very accurate optical instruments which today are working
at their performance limits.

      The system disclosed offers a possibility for replacing the
incremental glas gauge by the wave length of the light in an
interferometer with an integrated phase evaluation.  This system
shows increased performance limit and economy of operation.

      The Figure shows the interferometer and the phase measuring
unit.  A linearly polarized laser beam 1 with a diameter of
approximately 0.6 mm is transformed into circular polarized light
with a &lambda./4 plate 2.  A sinusoidal grid 3 provides a measuring
beam 1A and a reference beam 1B.  A lens 4 focusses both of the beams
1A, 1B to a rotating mirror 5 where the beams 1A, 1B are
phase-shifted.  The rotating mirror 5 reflects the two beams 1A, 1B
and the lens 4 combines them at the sinusoidal grid 3.  A beam
splitter 6 reflects the measuring beam 1A and the reference beam 1B
into the integrated phase measuring unit.  Between lens 4 and
rotating mirror 5 there is a further &lambda./4 plate 7 in the path
of the reference beam 1b.  After going there and back the components
of the reference beam 1B show an additional phase shift of
180 d...