Color variation control method for ink-jet printers

Abstract

A method for eliminating visible color variation, or color banding, in areas of the printout that color and black inks are capable of touching, without significant reduction in color-tint printout throughput, are described. The invented method includes detecting or analyzing areas in a print swath defined by a single horizontal pass of the printhead that contain superposed color and black dots. Upon detection of such a condition, the method further includes subdividing the typically broader black swath, e.g. forty-eight orifices, into a number of narrower swaths, e.g. by selecting only certain closely vertically adjacent ones of the orifices and their corresponding ink jets, that preferably are of equal vertical height to the height of the corresponding color swath, e.g. sixteen orifices. Printing is performed then-black ink during a first carriage pass followed by color ink during a subsequent carriage pass-by time interleaving one or more of the preferably equal height black and color swaths in such manner that the time between horizontally adjacent black and color ink-jet firing, or dot printing, is substantially constant. Preferably, the method avoids black swath down-sizing or other spatial or temporal accommodations when there is no likelihood of visible color-banding, i.e. when it is determined that there is in the present swath no color and black liquid ink interposition that could result in bleeding.