Abstract: A system and method of calibrating pulsewidth modulation of a laser. The output power of the laser is determined and a signal indicative of the output power is provided to a printer system control computer. The control computer calibrates the pulsewidth modulated signal responsive to the signal indicative of the output power. In a preferred embodiment, the control computer includes a lookup table or a mathematical model. The control computer compensates for timing variations in the pulsewidth modulated signal induced by system components and environmental operating conditions.

Abstract: Embodiments of a material-moving electrophotography roller are shown and described, each embodiment having an outer surface having ridges. The ridges may extend in right-handed or left-handed orientation, or in other angled (non-radial and non-horizontal) manner. The ridges lie in such a pattern so that the ridges move material radially over the roller or against a restrictive surface, and so that there are no gaps in the contact between the ridges and the material or the restrictive surface during a revolution of the roller. The roller is preferably made of a shaft covered by a sleeve or tube of non-disintegrating material with external ridges. The ridged tube is twisted and secured to the shaft so that the ridges run preferably and substantially at a 45.degree.-75.degree. angle from perpendicular to the roller axis.

Abstract: A charge roller displacement mechanism prevents the build up of a sharply defined circumferential ring of contaminants on the surface of a charge roller in an electrophotographic printing system, thereby reducing the severity of the print defect caused by the contaminants. By cyclically laterally displacing the charge roller parallel to the longitudinal axis of a photoconductor drum as the photoconductor drum rotates, contaminants which reach the surface of the charge roller will not form a sharply defined circumferential ring that interferes with the uniform charging of a photoconductor drum charged by the charge roller. The charge roller displacement mechanism includes a first gear that engages the gear used to rotate paddles in a waste hopper of an electrophotographic printer cartridge. A second gear engages the first gear to provide a reduction of approximately 400 to 1.