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Proceedings Paper

Halftone moiré due to imager distortion
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Paper Abstract

Individual halftone color separations must possess a low degree of distortion to avoid undesirable moiré in the overlays that produce the process colors. Achieving low relative distortion requires precise registration between the exposure devices used to write the halftone separations. However, optical and mechanical errors within the multiple Raster Output Scanners (ROS's) or image bars of a printer result in differences in the trajectory and placement of the exposure spots among color planes. In this paper, color halftone moiré due to ROS errors is analyzed using a frequency vector representation of color halftones. We analyze three forms of process-direction distortion: skew, shear, and bow. Each distortion is inspired from a practical printing system (i.e. while shear and bow are observed in ROS systems, skew is observed in image bar imaging systems). The frequency vector formalism is used to derive bounds on distortion for a classical halftone screen configuration (square cell equal frequency halftones at 15°, 45°, and 75°). The bounds are examined for distortion of one halftone screen and the analysis can be readily applied to distortion of multiple screens. The bounds can be used to develop specifications for imaging components in the design of a ROS or image bar imaging system.

Paper Details

Date Published: 18 January 2010
PDF: 9 pages
Proc. SPIE 7528, Color Imaging XV: Displaying, Processing, Hardcopy, and Applications, 752811 (18 January 2010); doi: 10.1117/12.838867
Show Author Affiliations
Orhan Bulan, Univ. of Rochester (United States)
Robert Loce, Xerox Corp. (United States)
Beilei Xu, Xerox Corp. (United States)


Published in SPIE Proceedings Vol. 7528:
Color Imaging XV: Displaying, Processing, Hardcopy, and Applications
Reiner Eschbach; Gabriel G. Marcu; Shoji Tominaga; Alessandro Rizzi, Editor(s)

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