Non uniform modification of process black colorants to achieve c

Details Non uniform modification of process black colorants to achieve c Non uniform modification of process black colorants to achieve c

1996-05-24

1998-04-07

Frahm, Eric

Facsimile and static presentation processing

Facsimile

Recording apparatus

358518, 358520, H04N 123, H04N 146, G03F 308

Patent

active

057370885

ABSTRACT:
A digital color printing method is described for printing process black color over a background color, which modifies individual values of the process colors in a process black independent of other process colors whenever the black colorant is sufficiently opaque. An example described which controls excess total colorant in a process black while simultaneously controlling misregistration fringes, a result which is not possible with the standard approach of modifying all process colors uniformly. The result is obtained by preferentially reducing the process colorant value with the highest luminance instead of reducing all process colorants uniformly.
In certain printing systems, printing problems can occur when process black, composed of a mixture of colorants such as cyan, magenta, yellow, and black (CMYK), is printed over a color background. For example, in a xerographic color printing system, a process black containing black plus all process colorants at maximum or near-maximum value can sometimes produce objectionable deletions in a surrounding color field, because the excessive toner height of the foreground process black interferes with the transfer of toner in the surrounding background color. However, solving the excess colorant problem in the standard way by reducing all process colorants uniformly can often create a significant difference in the foreground and background values of at least one process colorant, potentially causing light-colored misregistration fringes at the foreground/background edge. By instead preferentially reducing the colorant with the highest luminance, the result is controlled pile height without misregistration fringing.

REFERENCES:
patent: 4500919 (1985-02-01), Schreiber
patent: 5315416 (1994-05-01), Taniuchi et al.
patent: 5402253 (1995-03-01), Seki

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