Incorporating human visual model and spatial sampling in banding artifact reduction

Halftone banding, which affects the uniformity of xerographic images, is a well-known artifact for xerography, which appears as periodic light and dark bands across a printed page perpendicular to the process or print direction. Effective approaches for banding compensation need to consider the following two unique characteristics: 1) The human visual system should be included into the control system synthesis to quantify the perceived banding; 2) Spatially periodic scanline spacing variation due to gear noise has been shown to be a major contributor. In this paper, we summarize the work to incorporated human visual model into control system design and point out one aspect of the human visual system model that need to be addressed. To handle position dependent periodic disturbances, we employ spatial sampling and reformulate the motion transmission system using angular displacement as the independent variable. A linear parameter varying repetitive controller (LPVRC) is proposed to compensate for the angular displacement dependent periodic disturbances caused by the gears. Experimental verifications of the proposed approach are presented.