Electrostatic copying method including compensation for photoconductor

Abstract

A method of producing toner-developed electrostatic images involving the repetitive performance of a copying cycle comprising the steps of corona charging a photoconductive layer at a determined voltage level, information-wise photo-exposing said charged photoconductive layer, developing the exposed photoconductor with charged toner particles to a toner image, transferring the applied toner image to a receptor, and restoring the photoconductive layer to a rest potential for the next cycle; and between successive copying cycles, maintaining said photoconductor in the dark for a randomly varying time period. The number of performed copying cycles in each series is registered by electronic means and an output signal is generated; the period of time between series that the photoconductor is maintained in the dark is measured and a corresponding output signal is generated. The respective output signals are inputed to electronic control means which (a) based on a relation between the actual surface potential of the photoconductor and the number of copying cycles performed in a series, measures the voltage change in the photoconductor surface from the actual number of cycles in a series, (b) based on a relation between the actual change in surface potential of the photoconductor and the dark recovery duration measures the voltage change in the surface potential after an actual dark recovery period, (c) and then gives a combined control signal indicating the overall change in surface potential from the beginning of one series of cycles to the beginning of the next series. Finally, the corona voltage is regulated substantially according to the combined control signal.