Method and apparatus for thermal ink jet drop volume control using variable prepulses

Abstract

A method and apparatus are providing for extending the drop volume control of a thermal ink jet print head. The print head has a plurality of drop ejectors, each of the plurality of drop ejectors has a heating element actuatable in response to input signals to eject an ink droplet from the print head. The method includes the steps of applying a plurality of print signals to the print head, the plurality of print signals corresponding to an image for the ink jet assembly to create, applying at least one pulse signal to the print head, and sequentially using the at least one pulse signal and the plurality of print signals to activate the heating elements so that the change in current remains small. In addition, the apparatus has a print data storage element that receives print data from a printer controller, a pulse data delay element that receives pulse data from either a print head controller or a previous drop ejector and sends the pulse data to a next drop ejector after a predetermined delay, a heating element and a checksum element that, when the data storage element contains print data, and the pulse data delay element contains pulse data, activates the heating element according to the print data and the pulse data.