Browse Prior Art Database

IMAGE SCREENING TO REDUCE HALOS

IP.com Disclosure Number: IPCOM000023847D
Original Publication Date: 1979-Feb-28
Included in the Prior Art Database: 2004-Apr-01
Document File: 2 page(s) / 242K

Publishing Venue

Xerox Disclosure Journal

Abstract

In electrophotographic printing, it is frequently necessary to employ a screening system which modulates the resultant latent image recorded on a photoconductive surface. A typical screening system may be additive wherein a light source illuminates the screen to project a screened pattern on a photoconductive surface in superimposed registration with the latent image recorded thereon, In the alternative, a multiplicative screening system may be employed wherein the light image of the original document passes through the screen as it illuminates the

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XEROX DISCLOSURE JOURNAL

IMAGE SCREENING TO REDUCE HALOS Proposed Classification
L. Bean U.S. CL 355/3
R. Miller mt. CL G03g 15/00

In electrophotographic printing, it is frequently necessary to employ a screening system which modulates the resultant latent image recorded on a photoconductive surface. A typical screening system may be additive wherein a light source illuminates the screen to project a screened pattern on a photoconductive surface in superimposed registration with the latent image recorded thereon, In the alternative, a multiplicative screening system may be employed wherein the light image of the original document passes through the screen as it illuminates the

charged portion of the photoconductive surface. In either case, the resultant latent image is modulated by the screening pattern.

Hereinbefore, it has been found that without the use of a screening pattern, halos frequently form around the characters of the copy. Halos of this type are more prevalent when a single component magnetic toner is employed rather than the

conventional two~component magnetic toner. This is due to the fact that single component magnetic toner particles are generally field~dependentresistive toners.

The toner halo size may be significantly reduced by the utilization of a screening system. In practice, the frequency of the screen pattern used to supplement the image exposure should be at least 2Y

                          2 times greater than the resolution desired in the final copy. In additio...