Verfahren und Gerät zum Modulieren der Punktgrösse beim Tintenstrahldrucken

An ink jet (10, 200) provides high-resolution gray scale printing or switchable resolution printing by providing PZT drive waveforms (100, 110, 120, 360, 370), each having a spectral energy distribution that excites a modal resonance of ink in an ink jet print head orifice (14, 208). By selecting the particular drive waveform that concentrates spectral energy at frequencies associated with a desired oscillation mode and that suppresses energy at the other oscillation modes, an ink drop (170, 180, 190, 210) is ejected that has a diameter proportional to a center excursion size of the selected meniscus surface oscillation mode. The center excursion size of high order oscillation modes is substantially smaller than the orifice diameter, thereby causing ejection of ink drops smaller than the orifice diameter. Conventional orifice manufacturing techniques may be used because a specific orifice diameter is not required. Jetting reliability and contaminant susceptibility are, thereby, improved by eliminating the need for an unconventionally small orifice. Changing a selected PZT drive waveform amplitude changes drop ejection velocity without substantially changing drop volume. This invention, therefore, provides for selection of ejected ink drop volumes having substantially the same ejection velocity over a wide range of drop ejection repetition rates.