Abstract: A photosensitive medium, normally a diazo printing plate or photopolymer-based proof, is exposed in a series of exposures each of a small rectangular area. Typically several linearly-arrayed Deformable Mirror Devices (DMD's) each spatially encode a light beam in order to expose corresponding pixels within corresponding regions of the medium. Between successive exposures, the several DMD's are moved to a new position relative to the medium along a first, x, axis so that new exposures of new regions can be made. Normally the arrayed DMD's are moved relative to the imager's frame by a screw drive. There is an additional, separate relative movement between the DMD's and the medium along another, perpendicular, y, axis. Normally the medium is moved relative to the imager's frame by nip rollers. In order to provide a required precision in registering successively imaged regions of the medium along either or both axis, reference marks are exposed directly on the medium.

Abstract: A web of material, typically paper, metal or film and most commonly roll photographic plate material, passes between a first, driven, roller made from material with a high coefficient of friction, typically neoprene rubber, and a second, driven, roller made from material with a low coefficient of friction, typically metal or nylon. The high-friction drive roller (only) is positionally adjustable. The web is driven straight ahead, without appreciable undesirable steering or skew, over a broad range of adjustments of the separation, and the parallelism, between the two rollers. The web motion is responsive substantially to only the high-friction drive roller, and the web speed may accordingly be regulated, including so as to be maintained highly uniform, in response to the drive roller (only).

Abstract: A photosensitive, photoconductive media moving in a first direction relative to a laser light beam scanning in a second direction, transverse to the first direction, incurs velocity variations. These velocity variations result in variations in the absolute and relative heights of white and black image features. This printed image nonuniformity is especially visually detectable for closely spaced parallel lines in the second direction, and/or gray scale. An optical velocity sensor senses instantaneous media velocity. An analog or digital velocity error processor maintains a running average velocity and determines, by subtraction, an instantaneous velocity error as the difference between currently sensed and running average velocities. The instantaneous velocity error so determined is used to adjust the intensity of the laser light beam to be proportionally brighter (dimmer), exposing a wider (narrower) scan line, on a faster-moving (slower-moving) media region.