Browse Prior Art Database

Correction of Mechanical Properties in Polygonal Scanners

IP.com Disclosure Number: IPCOM000116720D
Original Publication Date: 1995-Oct-01
Included in the Prior Art Database: 2005-Mar-31
Document File: 2 page(s) / 75K

Publishing Venue

IBM

Related People

Wagner, D: AUTHOR

Abstract

Precision and performance of polygonal scanners substantially depend on their mechanical properties like bevelling angle (angle parallel to scan direction), apex angle (angle orthogonal to scan direction) and speed of rotation.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Correction of Mechanical Properties in Polygonal Scanners

      Precision and performance of polygonal scanners substantially
depend on their mechanical properties like bevelling angle (angle
parallel to scan direction), apex angle (angle orthogonal to scan
direction) and speed of rotation.

      For particle inspection purposes all the three parameters of
the polygonal scanner have to be improved.  In the compact unit
described hereinafter defining the start-of-scan-line (or correcting
the bevelling angle) and correcting the apex angle may be achieved
substantially free of losses.  The correction of the speed of
rotation may be achieved by arithmetic means.  Each of the
adjustments proposed improves the properties of the scanner by a
factor of approximately 5 to 10.  The light to be deflected is
incident at right angle thus reducing the cross section of the beam
to a minimum and shortening the delay period by a factor of 1.41.
This
leads to an increased throughput without changing other conditions.

      The unit shown below belongs to a polygonal scanner system with
a polygonal mirror of 20 bevels.  The polygonal scanner system is
intended to scan an area of about 4000 pixels.  At the start of each
bevel a light pulse of high precision and transconductance is
provided by about 1% of the laser light to be deflected at the
bevels and incident at an angle of about 30º  onto the bevels
in the direction of rotation.  To define the offset of this light
pulse caused by the rotation of the polygonal mirror the parallel
laser light is focussed by a lens.  By rotating the polygonal mirror
and adjusting the light at the start-of-scan-line to a maximum, very
short and high light pulses are p...