Banding Reduction in Electrophotographic Process

This paper proposed a new process control strategy for reducing banding artifacts in electrophotographic (EP) processes. EP banding artifact is shown to correlate to the fluctuation of the organic photoconductive (OPC) drum angular velocity. Improved regulation of the OPC drum rotational velocity under various process uncertainty and variations will significantly improve EP process stability and reduce the appearance of banding. The proposed control strategy includes two levels of OPC drum speed regulation. The first level utilizes a loop shaping technique to incorporate a human visual system (HVS) model into the control loop to eliminate low frequency and non-periodic drum velocity fluctuation. The second level uses an internal model based repetitive controller to reduce the effect of periodic velocity fluctuations. The HVS based loop shaping design is intended to address the subjective evaluation of printing process by incorporating human visual perception into EP process control. Experimental verification on a typical low cost 600-dpi EP engine showed significant banding reduction for spatial frequency up to 70 cycles per inch.