Abstract: A pixel density correction device for processing a signal containing pixel density values conveyed to a printing head of an electrocoagulation printing apparatus that includes a plurality of simultaneously addressable electrodes. The pixel density correction device of the invention comprises an input for receiving the signal representative of pixel density values associated with the simultaneously addressable electrodes, and a processing element for altering a pixel density value of a selected one of the simultaneously addressable electrodes, the signal processing element being responsive to pixel density values associated with electrodes other than the selected electrode to determine a corrected pixel density value associated with the selected electrode.

Abstract: An electrocoagulation printing apparatus has a printing head with an array of electrodes in contact with an electrically conductive electrocoagulation printing ink, and a driver circuit for impressing electric signals to individual electrodes of the array. The driver circuit includes a current limiter for limiting the magnitude of electric current passing through individual electrodes and the electrocoagulation printing ink to a predetermined value. The current limiter corrects a density of adjacent ink film pixels of a printed line to compensate for a cross-influence of impedance between adjacent ink film pixels.

Abstract: The invention relates to a printing head system for an electrocoagulation printing apparatus. The printing head system of the invention comprises an electrode carrier, a linear array of electrolytically inert electrodes electrically insulated from one another and mounted to the electrode carrier, the array of electrodes being arranged into a plurality of groups each having a predetermined number of closely spaced electrodes, and a driver circuit for addressing the electrodes of selected groups. The driver circuit is responsive to a graphical data input signal to cause simultaneous passage of electric current through at least a major portion of the electrodes in a selected one of the groups, the major portion of electrodes including electrodes that are contiguous with one another. Such a printing head system is capable of improving the quality of the image reproduced by electrocoagulation of an electrolytically coagulable colloid.