Patent ID: 6361147
Filing Date: 2002-03-26
Classification: B41J,G03G

Abstract:
A direct electrostatic printing device comprising a pigment particle source, a voltage source, a printhead structure, and a control unit, the pigment particle source providing pigment particles, the printhead structure and an image receiving member moving relative to each other during printing, the image receiving member having a first face and a second face, the printhead structure being placed in between the pigment particle source and the first face of the image receiving member, the voltage source being connected to the pigment particle source and a back electrode thereby creating an electrical field for transport of pigment particles from the pigment particle source toward the first face of the image receiving member, the printhead structure including control electrodes connected to the control unit to thereby selectively open or close apertures through the printhead structure to permit or restrict the transport of pigment particles which enable the formation of a pigment image on the first face of the image receiving member, wherein distance variations occur between the apertures in the printhead structure and the pigment particle source during printing, the distance variations at least in part being caused by a relative movement between at least a part of the pigment particle source and the printhead structure, the distance variations causing undesired image density variations in a direction parallel to the relative movement between the image receiving member and the printhead structure, the control unit controlling the transport of pigment particles to compensate for the undesired image density variations to create a perceived uniform printed image density along a printed image for a specific desired image density.