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Browse Prior Art Database

ADJUSTABLE ROTATING LIGHT BEAM DEFLECTOR

IP.com Disclosure Number: IPCOM000024608D
Original Publication Date: 1981-Apr-30
Included in the Prior Art Database: 2004-Apr-02
Document File: 4 page(s) / 171K

Publishing Venue

Xerox Disclosure Journal

Abstract

Current rotating light beam deflectors (including polygon mirrors, optical disks, etc.) suffer performance/cost problems due to fabrication and assembly tolerance/- errors as well as errors due to dynamic deflections. In a typical system utilizing a multi-facet rotating polygon, each facet of the rotating polygon deflects the incident light beam from a stationary source such as a laser through a specific deflection angle onto an imaging/photoreceptor plane at which location a scan line is formed by each facet deflection. The spacing between each successive pair of scan lines should be as uniform as possible.

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Page 1 of 4

XEROX DISCLOSURE JOURNAL

ADJUSTABLE ROTATING LIGHT BEAM DEFLECTOR U.S. Cl. 358/285
Milton J. Profant

Proposed Classification

Int. Cl. H04n 1/04

9

7

FIG. I

FIG. 2

Volume 6 Number 2 March/April 1981 89

[This page contains 1 picture or other non-text object]

Page 2 of 4

ADJUSTABLE ROTATING LIGHT BEAM DEFLECTOR (Cont'd)

Current rotating light beam deflectors (including polygon mirrors, optical disks, etc.) suffer performance/cost problems due to fabrication and assembly tolerance/- errors as well as errors due to dynamic deflections. In a typical system utilizing a multi-facet rotating polygon, each facet of the rotating polygon deflects the incident light beam from a stationary source such as a laser through a specific deflection angle onto an imaging/photoreceptor plane at which location a scan line is formed by each facet deflection. The spacing between each successive pair of scan lines should be as uniform as possible.

A typical motor/polygon assembly includes a motor housing base plate and a rotor shaft mounted in ball bearings. The polygon mirror is attached to a hub which, in turn, is fitted onto the rotor shaft. In order to achieve uniform scan line spacing in the photoreceptor planes each polygon mirror facet should be exactly parallel to the centerline of polygon rotation at the system operating speed. If this condition is not met, the reflected ray position path will vary for each facet, causing scan line spacing errors in the photoreceptor plane, thus degrading copy quality. This sagittal/pyramidal error component arises from both static and dynamic sources.

Static error sources include: (a) polygon facet surface fabrication tolerances/errors and (b) interface/assembly errors originating from fabrication tolerances of base, motor housing, rotor shaft, bearings, hub, polygon body, etc. Dynamic error sources are primarily due to: (c) rotor shaft deflection at operating speed.

The most significant individual error is generally item (a> and its magnitude is dependent on fabrication tolerance requirements.

A typical method of attempting to reduce the sagittal (scan line spacing) error is to mount the polygon mirror on a spherically compliant member located between the polygon and rotor shaft. This type of approach can help to reduce the errors in items (b) and (c) but can do nothing to reduce the errors of item (a). The result is that, at best, the errors of items (b) and (c) may be reduced but not eliminated with the major errors of item (a) not reduced at all. This type of approach could require dynamic adjustment of the polygon assembly depending on the particular design.

The apparatus described herein is designed to eliminate all sagittal errors including those in item (a) as well as those in items (b) and (c). Dynamic adjustment is provided for each polygon facet and spherically compliant polygon mirror mounting is required.

Another option presented by the apparatus shown herein is to statically adjust each polygon facet...