Periodic image artifacts from continuous-tone laser scanners.
Continuous-tone images produced by mechanically scanned analog modulated laser beams are susceptible to image artifacts in the form of spatially periodic density variations due to machine errors in film transport velocity, raster scan-line placement, and scan-line intensity. The human eye is particularly sensitive to periodic patterns and, in ideal conditions, can detect peak-to-peak density variations as small as approximately 0.005 for spatial frequencies around 2-5 cycles/deg. The stringent requirements that this implies for the scanner hardware are derived. Particular attention is paid to the rotating polygon-type scanner, since this device currently provides the best combination of speed, image quality, and cost.
Schubert
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3M Company, Graphics Sector Research Laboratory, Graphics Resources Technology Department, St. Paul, Minnesota 55144, USA.