US Patent 7753467 Ink jet printing apparatus and ink jet printing method

In an ink jet printing apparatus that ejects a plurality of kinds of pigment inks in small droplets, the drive pulse waveform to be applied to each of the heaters is adjusted according to the viscosity of the ink in a way that assures that the lengths of liquid columns ejected are approximately equal among different colors. This enables the dot areas formed on a print medium to be constant among different colors, realizing an image output with excellent color reproducibility, free from variations in image density and tonality.