Random printmasks in a multilevel inkjet printer

DETAILED DESCRIPTION " section of this document.
In preferred embodiments of a second of its aspects, the invention is apparatus for printing a color image on a printing medium, by construction from individual inkdrops formed in a pixel grid of multiple rows and columns.
The apparatus includes inkjet printing means for forming inkdrops on such medium in a pixel grid, during plural passes of the printing means over such medium.
The apparatus also includes--for each of the plural passes, some means defining an indicator of whether to print or not at each pixel.
It is to be understood that the respective indicators for the plural passes form a sequence of indicators for each pixel.
This sequence, for each pixel, is selected generally at random from a multiplicity of such sequences.
The apparatus also includes some means for applying the sequence of indicators to control the inkjet printing means.
The foregoing may represent a definition or description of the second aspect of the invention in its most general or broad form.
Even in this form it can be seen that this aspect of the invention too significantly mitigate a difficulty left unresolved in the art.
In particular this aspect of the invention provides an extremely efficient and elegant way of both selecting and designating randomized printmask data.
In fact, this form of identifying printmask data is also highly efficient and elegant for selecting and designating printmask data in general--whether or not randomized.
Nevertheless preferably the invention is practiced in conjunction with certain further characteristics or features that additionally enhance enjoyment of its benefits.
For example preferably the sequence for each pixel is preselected substantially at random from the multiplicity of sequences; and these preselected sequences--for all pixels--are prestored in nonvolatile memory for use in the apparatus.
We also prefer, as with the first aspect of the invention, that each sequence in said multiplicity of sequences be numbered; and that the sequence for each pixel be selected by substantially randomly selecting a sequence number