US Patent 7802869 Printer and printing method

An inkjet printer includes a printing head having nozzle units, a main scanning control unit, a sub scanning control unit, and a printing pass setting unit. Each nozzle unit includes a nozzle array where the nozzles are arranged in a nozzle array direction. The main scanning control unit makes the printing head to scan in a main scanning direction while the nozzle units discharge ink drops. The sub scanning control unit relatively moves the printing head with respect to the medium in a sub scanning direction. The printing pass setting unit correlates each of the nozzles with each of multiple printing passes to be printed at once by a scanning of the printing head in the main scanning direction, and sets discharging nozzles among the nozzles to discharge ink drops to the printing passes not to overlap boundaries of the printing passes with boundaries of the nozzle units.