Browse Prior Art Database

Optical Square

IP.com Disclosure Number: IPCOM000114866D
Original Publication Date: 1995-Feb-01
Included in the Prior Art Database: 2005-Mar-30
Document File: 2 page(s) / 50K

Publishing Venue

IBM

Related People

Houser, DE: AUTHOR [+2]

Abstract

Disclosed is a non-contact technique used to determine X to Y stage orthogonality of most any tool's XY stage. Previous techniques incorporate the use of precisely ground granite squares and contact indicator gauges. Measurement error includes both indicator and granite square error. These errors can be eliminated through the use of an optical square.

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Optical Square

      Disclosed is a non-contact technique used to determine X to Y
stage orthogonality of most any tool's XY stage.  Previous techniques
incorporate the use of precisely ground granite squares and contact
indicator gauges.  Measurement error includes both indicator and
granite square error.  These errors can be eliminated through the use
of an optical square.

      This technique requires a plate with defined features in a
symmetric pattern and a camera to view the features.  For purposes of
this application, a flat glass plate was used.  The camera can either
permanently reside on the tool being calibrated or temporarily
attached to the tool.  Features F1 and F3 are aligned to one axis(X),
either manually or by optical registration of the plate's coordinate
system (Figure).  The latter, being the more desirable technique,
requires the tool's software to rotate the plate's coordinate system
to match that of the tool's coordinate system.  Once accomplished,
Features F2 and F4 can be viewed and measured.

      This glass plate is then flipped so that Features F1 and F3 are
transposed, with Features F2 and F4 becoming F2r and F4r,
respectively (Figure).  The four features are now remeasured.  The
distance G represents the glass plate error before rotation, and Gr
represents the error after rotation.  The lines Xt and Yt represent
the tool's coordinate system, with Yt showing some degree of
non-orthogonality to Xt.  With G = Gr and the...