Printer color registration by compensation for eccentricity in idler roll

A method for operation of a color printer having imaging stations disposed along a photoreceptor belt for producing images on said belt, said belt passing around an idler roll, wherein one or more of said imaging stations is disposed on a first span of said belt on one side of said idler roll and a plurality of said imaging stations is disposed on a second span of said belt on an opposite side of said idler roll, each of said imaging stations including a charger, an imager, and a developer, and wherein the printer includes a belt driver which drives said photoreceptor belt around said idler roll and past said imaging stations, the method providing compensation for eccentricity in said idler roll to preserve registration among the images of said imaging stations, wherein an eccentricity of said idler roll induces different cyclic disturbances in the first and the second spans of said belt on the opposite sides of said idler roll, the method comprising steps of:

• sensing the position of an index of said idler roll;
• providing a set of values of an eccentricity correction function as a function of angle of rotation of said idler roll;
• and
• in response to a sensed position of said index, outputting values of said eccentricity correction function for altering the location on said belt of the image of sold one imaging station on said first span relative to the images of said plural imaging stations on said second span to compensate for said eccentricity, the method including a step of applying the correction function to said belt driver to alter a speed of said belt to compensate for a differential speed between said first span and said second span of the belt, thereby to accomplish said altering of the location of the image of said one imaging station.

A conveyor apparatus comprising work stations disposed along a conveyor for providing objects on said conveyor, said conveyor passing around an idler roll, wherein at least one of said stations is disposed on a first span of said conveyor on one side of said idler roll and a plurality of said stations is disposed on a second span of said conveyor on an opposite side of said idler roll, said apparatus including a system for compensating for eccentricity in said idler roll to preserve registration among the objects of said stations, wherein an eccentricity of said idler roll induces different cyclic disturbances in said conveyor on opposite sides of said idler roll, said system comprising:

• a sensor for sensing an index of said idler roll;
• a conveyor driver which drives said conveyor around said idler roll and past said stations;
• and
• a corrector responsive to a position of said idler roll relative to its index for outputting an eccentricity correction function for altering the location on said conveyor of the object of said one station on said first span relative to the objects of said plural stations on said second span to compensate for said eccentricity, the correction function being applied to said conveyor driver and being operative to alter a speed of said conveyor to compensate for a differential speed between said first span and said second span of the conveyor, thereby to accomplish said altering of the location on said conveyor of the object of said one station.