Optical: systems and elements – Deflection using a moving element – Using a periodically moving element
Reexamination Certificate
1999-12-06
2001-06-19
Phan, James (Department: 2872)
Optical: systems and elements
Deflection using a moving element
Using a periodically moving element
C359S198100, C359S216100, C384S100000, C310S090000
Reexamination Certificate
active
06249366
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to raster output scanners. More particularly it relates to reducing wobble and jitter from raster output scanners having motor polygon assemblies with stationary shafts.
BACKGROUND OF THE INVENTION
Electrophotographic marking is a well-known, commonly used method of copying or printing documents. Electrophotographic marking is performed by exposing a charged photoreceptor with a light image representation of a desired document. The photoreceptor is discharged in response to that light image, creating an electrostatic latent image of the desired document on the photoreceptor's surface. Toner particles are then deposited onto that latent image, forming a toner image, which is then transferred onto a substrate, such as a sheet of paper. The transferred toner image is then fused to the substrate, usually using heat and/or pressure, thereby creating a permanent record of the original representation. The surface of the photoreceptor is then cleaned of residual developing material and recharged in preparation for the production of other images.
One way of exposing the photoreceptor is to use a Raster Output Scanner (ROS). A ROS is typically comprised of a laser source (or sources), a pre-polygon optical system, a rotating polygon having a plurality of mirrored facets, and a post-polygon optical system. In a simplified description of operation light from the laser source is collimated and focused onto the rotating polygon by the pre-polygon optics; the light beam is reflected by the polygon's mirrored facets, and the reflected light is then directed by the post-polygon optical system into a finely focused light spot on the photoreceptor's surface. As the polygon rotates, the spot traces a path on the photoreceptor surface referred to as a scan line. By moving the photoreceptor as the polygon rotates the spot raster scans the surface of the photoreceptor. By modulating the laser beam with image information a predetermined latent image is produced on the photoreceptor.
Polygons typically are rotated at thousands, possible tens of thousands, of revolutions per minute. To achieve such rotational velocities polygons are usually mounted on air bearings. While several types of air bearing are known in the art, one type uses a housing with a centered, cantilevered stationary shaft and a rotating sleeve on the shaft. A multifaceted polygon is mounted on the rotating sleeve and the rotating sleeve forms part of a motor. Such a group of components is referred to as a motor polygon assembly (MPA). To create the air bearing, grooves (or flats) for generating air pressure are formed either around the outer surface of the stationary shaft or around the inner surface of the rotating sleeve. As the rotating sleeve turns air pressure is created between the shaft and the sleeve. That air pressure provides a low friction bearing that centers the rotating sleeve on the stationary shaft.
While motor polygon assemblies are beneficial, they are subject to various rotational defects. For example, wobble and jitter introduce scan line anomalies. While the post-polygon optical system is designed to reduce wobble and jitter, they are not totally effective. Additionally, the ROS optical components and their mounts have mechanical resonant frequencies that can be driven by a rotating motor polygon assembly. A prior art method of reducing rotational defects is to stiffen the housing and the cantilevered stationary shaft. While useful, this approach becomes increasingly more costly and bulky as stiffness is increased. Therefore, a new approach to reducing rotational defects in motor polygon assemblies having cantilevered stationary shafts would be beneficial.
SUMMARY OF THE INVENTION
The principles of the present invention provide for reduced rotational defects in motor polygon assemblies having cantilevered stationary shafts. Those principles further provide for raster output scanners that produce scan lines with reduced anomalies. A motor polygon assembly according to the principles of the present invention includes a housing, a cantilevered stationary shaft within the housing, a rotating sleeve, a multifaceted polygon mounted on the rotating sleeve, and a cover over the housing. The cover includes a protrusion that contacts the free end of the cantilevered stationary shaft so as to stabilize the cantilevered stationary shaft.
REFERENCES:
patent: 4523800 (1985-06-01), Yamashita et al.
Gerald F. Marshall-Edited by; Copyright 1985 by Marcel Dekker, Inc.; Laser Beam Scanning Opto-Mechanical Devices, Systems, and Data Storage Optics; pp. 125-147, 149, 154; printed in the United States of America (No Month).
U.S. application Serial No. 09/216,586; filed Dec. 18, 1998; “Circular Polygon,” by Charles C. Pecoraro et al.
Burns Cedric R.
Hinton John H.
Pecoraro Joseph R.
Henn David E.
Kelly John M.
Phan James
Xerox Corporation
LandOfFree
Outboard support for cantilevered air bearing stationary shaft does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Outboard support for cantilevered air bearing stationary shaft, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Outboard support for cantilevered air bearing stationary shaft will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2520858