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OPTICAL SYSTEM TO REDUCE POLYGON SCAN ANGLE OF SMALL NUMBER OF FACET

IP.com Disclosure Number: IPCOM000022875D
Original Publication Date: 1976-Mar-31
Included in the Prior Art Database: 2004-Mar-27
Document File: 2 page(s) / 259K

Publishing Venue

Xerox Disclosure Journal

Abstract

It is desirable to have a large polygon facet width in a laser scanning system especially when the system requires a very small spot. In most cases the system is a diffraction limited system and the facet width is the limiting aperture of the system. When making the facets wider, the diameter of the polygon becomes larger0 In some cases this becomes very impractical0 In order to minimize the diameter of the polygons, the number of facets on the polygon may be reduced and the facet width increased0 This will introduce another problem, that is, the angular scanning efficiency will be reduced, or, in other words, the dead time between scans will increase which makes the system very inefficient0 However, this may be overcome by reducing the number of facets to accommodate wider facets and reducing the scanning angle to increase efficiency. The polygon 1 reflects a laser beam 2 through a scan angle of c'~ to a reflective or refractive aplanatic system 3 which changes the beam scan angle to ~ (~

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XEROX DISCLOSURE JOURNAL

OPTICAL SYSTEM TO REDUCE Proposed Classification
POLYGON SCAN ANGLE OF U.S. Cl

                                     0 350/6
SMALL NUMBER OF FACET mt. Cl. G02b 27/17
Philip L. Chen

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2 ~ENDQFSCAN I

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2 JSTARTOF

-j~ ~SCAN

It is desirable to have a large polygon facet width in
a laser scanning system especially when the system
requires a very small spot. In most cases the system is
a diffraction limited system and the facet width is the
limiting aperture of the system. When making the facets
wider, the diameter of the polygon becomes larger

                                       0 In
some cases this becomes very impractical

                          0 In order to
minimize the diameter of the polygons, the number of
facets on the polygon may be reduced and the facet width
increased
0 This will introduce another problem, that is,
the angular scanning efficiency will be reduced, or, in
other words, the dead time between scans will increase
which makes the system very inefficient

                          0 However, this
may be overcome by reducing the number of facets to
accommodate wider facets and reducing the scanning angle
to increase efficiency. The polygon 1 reflects a laser
beam 2 through a scan angle of c'~ to a reflective or
refractive aplanatic system 3 which changes the beam scan
angle to ~ (~<c~)to a scanning plane 4, The system 3 can
be either a lens system or mirror system. The scanning
speed variation can become severe due to the large scanning
angle of each polygon facet, but it can be compensated
for either optically or electronically. This system
automatically gives a flat...