Incremental printing of symbolic information – Light or beam marking apparatus or processes – Scan of light
Reexamination Certificate
1999-12-09
2001-04-17
Nguyen, Thinh (Department: 2861)
Incremental printing of symbolic information
Light or beam marking apparatus or processes
Scan of light
C347S257000, C359S849000, C359S873000
Reexamination Certificate
active
06219082
ABSTRACT:
Disclosed in the embodiments herein is an improved, simple, low cost, system for micron level adjustment of a mirror surface. In particular, for bow correction of a printer ROS scanning beam linearity on the printer photoreceptor by a very small mirror surface deformation adjustment in the photoreceptor raster scanning output imaging system, utilizing a simple differential screw system in which two slightly different screw pitches of a differential screw subtract from one another to convert a gross or macro mechanical rotation of the differential screw into a micron level movement for a micron level mirror surface curvature change. Thus, solving a major problem in that widely practiced commercial technology (publicly better known as “laser printers”) with a very simple and inexpensive, yet effective, solution.
That is, this is a low cost and simple to use fix for the well-known “bowing” problem in laser imaging, that is, observable non-linearity of the laser scan line on the photoreceptor surface. As shown in the disclosed embodiments, this bowing is hereby correctable by, but is not limited to being caused by, the reflectance surface of the post-polygon fold mirror in a ROS system, since bowing may have various ROS system sources. The disclosed system allows very fine, very precise, alignment changes in a ROS mirror surface curvature or flatness without requiring delicate and expensive adjustment equipment.
As disclosed in the specific embodiment, the bow correction system may employ a special differential screw member with two coaxial, but separate, and very slightly different pitch, screw thread surfaces respectively screw coupled to different elements of the system. Rotation of the differential screw member effectively subtracts one screw pitch movement from the other in this system, thus applying an adjustment movement of only the very small difference between the two screw pitches to the bowing deflection of the mirror.
As disclosed in the specific embodiment, this simple differential screw in combination with a yoke or other mirror holding system can make fine mechanical adjustments in the flatness or deformation of a fold mirror (or other mirror) in a ROS system substantially along the optical path to correct for residual scan line bow, or other errors.
Bow matching to the 5 to ten micron level is particularly important in color applications, such as those in which multiple beam ROS sweep or scanning beam patterns have to all be precisely registered relative to one another on the same photoreceptor or on plural (tandem) photoreceptors in the same color printer. The human eye is particularly sensitive to color print registration errors of composite color images.
By way of background, it is known to provide screw adjustments, with normal, single pitch, screws, of the angular position of the reflective plane of mirrors, such as in the initial manufacturing alignment of scanning mirror systems in xerographic light-lens copiers.
Raster output scanner (ROS) systems per se are well know, extensively patented, and need not be re-described herein.
A specific feature of the specific embodiment(s) disclosed herein is to provide in a printer with a raster scanning system for image scanning a photoreceptor surface with scan lines, which scan lines have a small undesired non-linear bow, and which raster scanning system has an optical path with at least one mirror therein, the improvement for at least partially compensating for said bow comprising: a bow compensation system for very slightly deforming the initial plane of said mirror in a direction to partially correct said bowing of said scan lines, said bowing compensation system including a mirror gripping system for gripping said mirror, and a differential screw system engaging said mirror gripping system, said differential screw system having a screw shaft with first and second separate fine screw thread patterns having slightly different screw pitches, one of which screw thread patterns operatively engages said mirror gripping system so that rotation of said screw shaft moves said mirror gripping system and its engaged portion of said mirror by the difference between said slightly different screw pitches to provide a very small deformation of said mirror by a rotation of said screw shaft.
Further specific features disclosed herein, individually or in combination, include those further comprising a frame member holding said mirror in a fixed position at a position on said mirror different from said mirror gripping system, wherein said frame member has a first threaded hole engaging said first screw thread pattern of said screw shaft, and wherein said mirror gripping system has a second threaded hole coaxial with said first threaded hole, said second threaded hole engaging said second screw thread pattern of said screw shaft; and/or wherein a method of making very small curvature modifications of the reflective surface of a mirror comprising gripping at least one portion of the mirror with a gripping system, and applying a very small movement to said gripping system by gross rotation of screw shaft of a differential screw system operatively connected to said gripping system, wherein said screw shaft has two separate fine screw thread patterns of slightly different screw pitches, whereby said gross rotation of said screw shaft moves said mirror gripping system and its engaged portion of said mirror by automatically subtracting said two slightly different screw pitches from one another to provide a very small deformation of said mirror by said gross rotation of said screw shaft.
As to specific components of the subject apparatus, or alternatives, it will be appreciated that, as is normally the case, some such components are known per se in other apparatus or applications which may be additionally or alternatively used herein, including those from art cited herein. All references cited in this specification, and their references, are incorporated by reference herein where appropriate for appropriate teachings of additional or alternative details, features, and/or technical background. What is well known to those skilled in the art need not be described here.
REFERENCES:
patent: 5084715 (1992-01-01), Mama
patent: 5596404 (1997-01-01), Beck et al.
Dunn Susan E. F.
George Clifford L.
Rumsey Karen M.
Williams Antonio L.
Nguyen Thinh
Pham Hai C.
Xerox Corporation
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