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Dark Charge Correction for Copier Reduction Mode

IP.com Disclosure Number: IPCOM000049665D
Original Publication Date: 1982-Jul-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 2 page(s) / 48K

Publishing Venue

IBM

Related People

Bierschbach, JE: AUTHOR

Abstract

In a copier using the electrophotography process and having various reduction or magnification modes, it is desirable to adjust the process for each mode to compensate for the variation in illumination. As the copies are reduced in size, the amount of illumination to which the photoconductor is exposed decreases. To maintain quality copies, the dark charge voltage applied to the photoconductor should also decrease.

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Dark Charge Correction for Copier Reduction Mode

In a copier using the electrophotography process and having various reduction or magnification modes, it is desirable to adjust the process for each mode to compensate for the variation in illumination. As the copies are reduced in size, the amount of illumination to which the photoconductor is exposed decreases. To maintain quality copies, the dark charge voltage applied to the photoconductor should also decrease.

Shown above is a state diagram for controlling the dark charge voltage used by a corona to place dark charge on the photoconductor prior to the photoconductor being exposed to the image. Each state A, B and C represents a different copy size. State A is the normal or 1:1 copy, while states B and C are the 1.2 reduction and 1.5 reduction modes of operation. Accordingly, in a negative charge system using a photoconductor, the the dark charge voltage V1 is the most negative voltage. Dark charge voltage V2 at state B is a smaller negative voltage, and dark charge voltage V3 at state C is the smallest negative voltage.

The controls to switch the copying system between various states are preferably implemented by programming a microprocessor to control the copier. The conditions for moving between states A, B and C are evident from the above state diagram. State A represents the normal mode of operation. If the mode of operation changes to the 1.2 mode or the 1.5 mode, program control switches the copier to state B or C, respectively, to provide the correct dark charge voltage....