Thermal-ink-jet print system with drop detector for drive pulse

Abstract

A thermal ink jet printing system includes a drop detector which is used in a feedback loop to optimize operational drive pulse parameters. By optimizing the drive pulse, drop velocity can be set within an optimal range above a inflection point in the transfer function of a print head drop generator. This provides near maximal drop velocity while minimizing heat dissipation at the heater resistors which would otherwise impair reliability and print head life. The drive circuitry includes a microcontroller including a pulse controller, a test generator and an algorithm function. During a maintenance procedure, for example, during start-up, the test generator causes the pulse controller to test each of many drop generators with a series of fixed-voltage rectangular pulses of digitally increasing pulse width. The pulse width at which a drop is first detected and the velocity of each drop detected is correlated with the width of the pulse which generated that drop. The algorithm function calculates an individual operational pulse width for each drop generator, or alternatively, a common operational pulse width for all drop generators, from the test data so collected. The pulse parameter value set so determined is programmed into the pulse controller and used during normal printing operation.