Multilevel ink mixing device and method using diluted and saturated color inks for inkjet printers

Abstract

A device and method of printing a color image using a lookup table that indicates the amount of at least two concentrations of a given ink color to use. Initially, several color wedges made from uniformly distributed digital counts for each color from lightest to darkest are printed. The color lightness value for each wedge is then measured as an L* value of the CIELAB system along with a granularity value. An interpolation process is then performed to determine the color lightness values and granularity values for color values between wedges. A diluted ink minimum color lightness point is identified by determining the darkest color that can be generated using only diluted ink. Ink patterns are then selected using only diluted ink for color lightness values lighter than the diluted ink minimum lightness point in the lookup table. A zero diluted ink starting point is then identified by determining that granularity improvement cannot be achieved significantly when adding more diluted ink to a pixel matrix. Ink patterns are then selected using a mixture of diluted and saturated ink that gives a print image within a predetermined percentage of a target color lightness value and within a predetermined percentage of the granularity of the pixel matrix using an optimum amount of diluted ink. Finally, ink patterns are selected using only saturated ink for color lightness values darker than the zero diluted ink starting point in the look up table.