Halftone pattern geometry for printing high quality images

Details Halftone pattern geometry for printing high quality images Halftone pattern geometry for printing high quality images

1997-11-28

1999-09-28

Hilten, John

Typewriting machines

Typing by other than type-face or type-die

Thermal

40012009, B41J 236

Patent

active

059575930

ABSTRACT:
A digital halftone pattern geometry adapted not to the characteristics of variable dot size printing presses but to the operating characteristics of the printer itself achieves a high degree of image quality. The techniques for creating the halftone pattern geometry include linear spot growth to provide uniform darkening and the use of a super-cell structure to maximize the number of tint or gray scale levels. A preferred super-cell structure is of hexagonal dispersed-dot form to reduce low frequency artifacts by spreading them over a greater number of frequencies. Hexagonal centered super-cells also distribute row and column artifacts along three axes of symmetry instead of two. The super-cell structure gives sharp edges and a greater amount of edge area available to manipulate when the super-cells are tessellated to form an image. This halftone cell arrangement is especially suited to thermal transfer printers, which print linear rows and form good rectangular shapes. The resulting image exhibits smooth darkening even for cells having few pixels.

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Ulichney, Robert, Digital Halftoning, 1987, pp. 1-11, 77-98, 110-139, 187-208, 343, and 344.

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