Algorithms for Maximizing Printhead Utility Using Histogram Equalization

This paper presents algorithms for extending the life of thermal array printheads. A major cause of thermal element fatigue is the uneven use of the print elements, which is due to the uneven dot distribution requirements in printing alphanumerics. To obtain a nearly uniform dot utilization an optimum algorithm for shifting the printed text was developed on a page basis. To this end, first, means were developed to determine the dot distribution of a given font set, second, the effect of printshifting by a few dot rows on the overall distribution was studied and third, algorithms were developed that lead to optimum printshifting. Finally, it is shown that with simple shifting strategies, the printhead life can be extended by about 105% at a negligible software cost.