Browse Prior Art Database

Original Publication Date: 1988-Oct-31
Included in the Prior Art Database: 2004-Apr-04

Publishing Venue

Xerox Disclosure Journal


A bar code scanner or reader for automatic density control. A test patch composed of a succession of different voltage levels on a photoreceptor (corresponding to lines of a bar code), are arranged in order that the number of lines developed to a visible state are used to produce proper development control. As an example, assuming five lines, the first three would be developed to visibility when toner concentration (developability) is normal, and only two lines developed to visibility if a standard addition of toner is needed. The presence of only one line might call for a larger than normal toner addition and a count of zero or more than three lines trigger appropriate signals to the operator. The lines of various voltages could be generated in several ways such as a small transparency with a flashing light, a transparency intermittently introduced into the path of the exposure light, an opaque test patch adjacent the document area for exposure through a lens, or a small charging device intermittently energized to various voltages.