Patent ID: 7410232

Claim:
An ink-droplet ejecting apparatus, comprising: a nozzle from which a droplet of an ink is ejected; a pressure chamber which is filled with the ink and is connected to the nozzle; an actuator which changes a volume of the pressure chamber and thereby changes a pressure of the ink in the pressure chamber; and a control device which, when a first print command corresponding to a first pixel and a first print period is to eject the ink and a second print command corresponding to a second pixel next to the first pixel and a second print period next to the first print period is to eject the ink, outputs, within the first print period, a first drive waveform so as to drive, a plurality of times, the actuator to produce a plurality of pressure waves, respectively, in the pressure chamber and thereby eject a plurality of droplets of the ink, respectively, from the nozzle to form the first pixel, and which, when the first print command is to eject the ink and the second print command is not to eject the ink, outputs a second drive waveform extending over the first and second print periods, wherein the control device outputs, as the second drive waveform, a first ejecting pulse signal, then a first canceling pulse signal, then a second ejecting pulse signal, and then a second canceling pulse signal, so as to drive, two times, the actuator to produce two pressure waves, respectively, in the pressure chamber and thereby eject two droplets of the ink, respectively, from the nozzle to form the first and second pixels, respectively, wherein each of the first and second ejecting pulse signals has a pulse length falling in a range of from 0.8AL to 1.2AL, where AL is a one-way propagation time needed for each of the two pressure waves to propagate one way in an ink flow passage which includes the pressure chamber and is connected to the nozzle, wherein the first canceling pulse signal has a pulse length falling in a range of from 1.3AL to 1.8AL, wherein the second canceling pulse signal has a pulse length falling in a range of from 0.3AL to 0.4AL, and wherein a time interval between a trailing end of the first canceling pulse signal and a leading end of the second ejecting pulse signal fills in a range of from 3.0AL to 4.5AL.