Patent ID: 7576763

Claim:
An imaging device for producing multicolor images from image data containing data representing an image of a first color and an image of a second color to be registered relative to the image of the first color onto a substrate by transferring colorants of the first and second colors to the substrate, the imaging device comprising: a first imager configured to generate an output corresponding to the image of the first color at a first exposure station, a second imager configured to generate an output corresponding to the image of the second color at a second exposure station; a photoreceptor belt configured to pass the first imager and the second imager; a photoreceptor drive system coupled to said photoreceptor belt, said photoreceptor drive system driving said photoreceptor belt in a process path past the first and second imagers in a process direction; an encoder coupled to said photoreceptor drive system, the encoder generating encoder pulses; said second imager being displaced along said process path from said first imager by a displacement corresponding to a nominal number of said encoder pulses, a controller coupled to receive the encoder pulses, the controller determining an actual machine clock period based on a time between successive ones of said encoder pulses, the controller generating a simulated machine clock signal based on a running average of a plurality of said actual machine clock periods, the controller using the simulated machine clock signal to count up to said nominal number following firing of said first imager for a given scanline of said image data to determine a target time for firing said second imager for said given scanline.