Abstract
In a raster scanning printer, a laser beam is scanned across a photoreceptor in a direction perpendicular to the photoreceptor motion. When there is vibratory motion of the photoreceptor or wobble in the polygon mirror, the raster lines on the photoreceptor will not be evenly spaced. We analyze the positioning error and show that fractional raster spacing error is equal to photoreceptor fractional velocity error. These raster position errors can result in various print defects, of which halftone banding is the dominant defect. The dependences of halftone banding are examined using a first-order geometry-based printing model, an exposure model, and a more sophisticated laser imaging model coupled with a xerography model. The system model is used to calculate print reflectance modulation due to vibrations in both charged-area and discharged-area
development modes using insulative or conductive development. System parameters examined are halftone frequency, raster frequency, average reflectance, vibration frequency, and multiple-beam interlace spacing.
