Biasing scheme for improving latitudes in the tri-level xerographic process

摘要

The operating latitude of the tri-level xerographic process is improved by replacing the standard DC bias that is applied to one or both of the developer housings in conventional tri-level imaging with a chopped DC (CDC) developer bias. Chopped DC biasing is the alternate application of two discrete bias voltages to a developer strucrute in a periodic fashion at a given frequency, with the period of each cycle divided up between the two bias levels at a duty cycle of from 5-10% or 90-95% depending upon which of the two developer structures is being biased. In the case of the DAD developer structure the duty cycle of higher of the two biases is 5-10% and in the case of a CAD developer structure the duty cycle of higher of the two biases is 90-95%.