Drum Technology: The Influence of Imaging Surface Geometry on Image Quality

Details:

Year: 1996
Pages: 13

Summary:

Five aspects of platesetter architecture affect the quality of images produced by high resolution, raster platesetters: image surface geometry, slow scan positioning system, writing beam configuration, vacuum system, and material docking system. Image surface geometry may be internal drum, external drum, or flatbed. Mechanical runout and variations in drum cylindricity significantly affect image quality, as do variations in slow scan positioning system parallelism. Writing beam configuration has four components: resolution, number of writing beams, external drum rotation speed or internal drum writing beam spinner/deflector speed, and material length or drum depth. Multi-beam configurations are susceptible to non-uniformity of beam intensity, beam-to-beam spacing, and cluster-to-cluster spacing, all of which cause visible artifacts. Multi-beam configurations also have a shorter depth of focus, which causes all drum surface variations to magnify errors resulting from runout and cylindricity variations. Image artifacts measured in millionths of an inch will be visible to the human eye. An external drum is also more susceptible than the internal drum to errors accruing from the vacuum system. The best image quality is achieved using an internal drum with a single writing beam.