Electrophotographic process control systems utilizing development bias currents
Jeffrey J. Folkins · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 1990
Both electrostatic and toner concentration (TC) electrophotographic process control systems can be constructed with the proper use of bias current measurements of the development subsystem. A TC I developability controller can be made by measuring the development bias current for each print or copy, summing the measurements, subtracting offset currents and dispensing toner proportionally to this developed charge measurement. If certain constraints are fulfilled, the system will operate at a constant developed toner mass. Similarly, a photoconductor electrostatic measurement I control system can be made by utilizing bias currents. This is accomplished by choosing a stable portion on the developed charge vs development voltage relationship of the development subsystem. This setpoint is then used to measure photoconductor test patch voltages by monitoring the bias current. In some cases this provides the same function as an electrostatic voltmeter. These low cost techniques enable the practical process control implementations in low and medium speed electrophotographic machines.