Patent ID: 8511776
Filing Date: 2013-08-20
Classification: B41J

Abstract:
1. A method for maintaining the optical density of images produced by a printing device, the method comprising: with a printhead module of said printing device, printing a color region onto a first test page, said color region comprising a plurality of sub-regions, each said sub-region being printed with a different drive voltage; measuring an optical density of each of said sub-regions printed onto said first test page; determining a response curve based on a relationship between said optical density of said sub-regions and said different drive voltages used to print said sub-regions; using said response curve, determining a target drive voltage for said printhead module which will cause said printhead module to print at a target optical density, with said printhead module, printing a new color region on a second test page using said target drive voltage; and comparing an optical density of said new color region to an optical density of a target color region of a target page, said target page being printed by a trusted printing device at said target optical density.