Adaptive exposure color correction
AssigneeXerox Corporation
InventorsCyril G. Edmunds, William L. Lama
Life of this patent
Estimating the term…
Abstract
An apparatus for correcting color images in an electrophotographic printing machine in which a first image is developed on a photoconductive surface, the second and subsequent images are superimposed over the first developed image. The apparatus includes an input device for inputting an image signal having a plurality of color components. An image processing unit processes the inputted signal. The image processing unit includes an adaptive exposure processor that modulates the exposure level of a raster output scanner (ROS) for a given pixel as a function of toner previously developed at the pixel site, thereby allowing toner layers to be made independent of each other.
Claims6
An electrophotographic printing machine, comprising:
- a photoconductive member;
- means for charging the photoconductive member;
- means for inputting an image signal;
- means, responsive to the image signal, for exposing the charged photoconductive member for recording an electrostatic latent image thereon;
- means for developing the electrostatic latent image with toner of a first color during a first cycle and toner of a second color during a second cycle to form a composite toner image on said photoconductive member;
- adaptive exposure processing means for modulating the exposure level of said exposing means for the second cycle as a function of the amount of toner developed on the electrostatic latent image recorded on said photoconductive member during the first cycle;
- and
- means for transferring the composite toner image from the photoconductive member to a copy sheet.
A method of producing a color copy in an electrophotographic printing machine, comprising the steps of:
- inputting an image signal including a plurality of color components;
- exposing a charged photoconductive surface to record an electrostatic latent image thereon;
- separating the image signal into a plurality of bit maps which represent the color of each pixel;
- examining and correlating the color of each pixel to the modulation of said exposing step;
- developing the latent image with toner of a first color during a first cycle and toner of a second color during a second cycle to form a composite toner image image on the photoconductive member;
- and
- determining a correction value from a look-up table as a function of the active part of the photo-discharge curve of the photoconductive surface, the dielectric thickness effect of the toner previously developed at the pixel site of the latent image recorded on the photoconductive surface during the prior cycle, and the backscattering/absorption of the toner developed on the latent image recorded on the photoconductive surface during the prior cycle;
- and
- transferring the composite toner image from the photoconductive member to a sheet.
Dependencies are inferred from the claim text.