Automatic Density Control for Increased Print Uniformity and Printer Reliability with Inline Linear Array Sensing

摘要

Color electrophotographic printing requires consistent and uniform color within a single page. One approach to increase and maintain uniform color is to measure any residual nonuniformity and then adjust the image to compensate for it. To make this measurement, we develop a test pattern consisting of a series of different density strips with fiducials to identify the position along the strip. The strip can be printed on a surface in the machine such as a photoreceptor belt. An image of the test pattern strip is captured as the strip passes under a linear array detector. The test pattern is cleaned from the belt and thus requires no user intervention to monitor. The density of toner as a function of position is extracted from the linear array response. From the toner density profile and the engine response curve, the gray level needed to compensate for any nonuniformity can be calculated. The change in the gray level is injected into the image path, so that the digital image is modified in a way to exactly compensate for the varying engine response. Control techniques maintain the uniformity throughout long prints runs.