Abstract: A liquid ink, drop-on-demand printhead includes a substrate having a plurality of drop-emitter orifices, an ink channel coupled to each of the orifices for delivery of a body of ink to the orifices at a pressure above ambient, thereby forming an ink meniscus at the orifices. Drop selection is effected by selectively delivering heat to ink which has been delivered to selectively addressed ones of the orifices, thereby causing a difference in meniscus position between ink in addressed and non-addressed orifices. A heater is suspended in each ink meniscus close to its surface when the meniscus is at its position in a non-addressed orifice, the heater being effective to heat the meniscus and to thereby reduce surface tension of the meniscus at selectively addressed orifices.

Abstract: A readout technique for use with a charge injection device avoids intensity-distortion resulting from both over-illumination and pattern noise. Although the invention utilizes column- (or row-) capacitance changing to produce information signals, it provides readout by supplying charge from a reference source (capacitor) to the pixel being read, thereby restoring the column potential of the pixel to a reference level. The readout signal corresponds to the voltage change across the reference capacitor as a result of its discharge.