Browse Prior Art Database

EXPOSURE CONTROL SYSTEM

IP.com Disclosure Number: IPCOM000026316D
Original Publication Date: 1991-Apr-30
Included in the Prior Art Database: 2004-Apr-05
Document File: 8 page(s) / 410K

Publishing Venue

Xerox Disclosure Journal

Abstract

The present invention relates to an optical imaging system for an electrophotographic copying machine and more particularly to an exposure system in which the reflectivity of a scan mirror in the optical system controls the illumination level and illumination profile at the surface of a photoreceptor.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 24% of the total text.

Page 1 of 8

XEROX DISCLOSURE JOURNAL

EXPOSURE CONTROL SYSTEM Thomas J. Hammond

Proposed Classification
U.S. C1.355/227 Int. C1. G03g 15/02

10

22

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12

4

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I /46

FIG. I

XEROX DISCLOSURE JOURNAL - Vol. 16, No. 2 MarchfApril1991 113

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EXPOSURE CONTROL SYSTEM(Cont'd)

       266, 26C 260 26A--,, , I I t

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30N

26N 26

.........---- l.-. '

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FIG. 2

114 XEROX DISCLOSURE JOURNAL - Vol. 16, No. 2 MarcidApril 1991

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Page 3 of 8

EXPOSURE CONTROL SYSTEM(Cont'd)

30N

0 y&g/ 4/'

6 7TT

MIRROR CONTROL CIRCUIT

UA 448 44c 440 44E 44N

FIG. 3

XEROX DISCLOSURE JOURNAL - Vol. 16, No. 2 MarcMApril1991 115

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Page 4 of 8

EXPOSURE CONTROL SYSTEM(Cont'd)

68

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*- 62

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LIGHT 30 IMAGE

30A--30N

64 l' d i

F/G. 4

116 XEROX DISCLOSURE JOURNAL - Vol. 16, No. 2 MarcidApril 1991

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

Page 5 of 8

EXPOSURE CONTROL SYSTEM(Cont'd)

The present invention relates to an optical imaging system for an electrophotographic copying machine and more particularly to an exposure system in which the reflectivity of a scan mirror in the optical system controls the illumination level and illumination profile at the surface of a photoreceptor.

In electrophotographic copiers, a document to be reproduced is placed on a document platen and is incrementally illuminated by a light source such as a fluorescent lamp, which moves in a parallel path beneath the platen. The light is reflected by at least a scanning mirror and the reflected light image projected through a lens to expose a surface of a photosensitive image medium such as a drum or belt photoreceptor. The optical system generally incorporates one or more folding mirrors to enable a compact design. The surface of the photoreceptor has previously received a charge of a certain magnitude and polarity. The incident light discharges the surface leaving fully charged areas representing the informational areas of the document (write-white system). The latent image of the document thus formed is subsequently developed and transferred to an output medium such as plain paper. The goal in the production of the output print for a 1:l copy is to make as exact a copy of the original document as possible. It is, therefore, desirable that the non-image areas of the photoreceptor which are exposed by the light experience a discharge to the same background level, e.g., achieve a uniform discharge level in all the illuminated areas.

The major source of non-uniform discharge is a non-uniform illumination level incident at the photoreceptor surface. The causes of non-uniform illumination are well known; the most significant being the fall-off in light at the ends of the image plane illumination profile caused by COS~ variations created by the projection lens. Other causes of non-uniformity include the dark regions near the electrodes in...