Patent ID: 8657401

Claim:
An image forming apparatus comprising: a printing head unit including: multiple nozzles to eject liquid droplets; multiple separate liquid chambers communicating with the multiple nozzles, respectively; a common liquid chamber to supply liquid to the multiple separate liquid chambers; and a pressure generator to generate pressure to compress the liquid stored in the multiple separate liquid chambers; a driving waveform generator to generate and output a driving waveform having at least four driving pulses per driving cycle arranged in chronological order; and a selector to select and apply at least one of the multiple driving pulses included in the driving waveform outputted from the driving waveform generator to the pressure generator to cause the printing head unit to selectively discharge liquid droplets of at least three different sizes, wherein three or more driving pulses including a final driving pulse included in the at least four driving pulses at the end of the driving waveform discharges a biggest liquid droplet, and a micro-driving pulse included therein discharges a smallest droplet, wherein the micro-driving pulse is outputted within a time period of from about 2×Tc to about 4×Tc after the driving waveform starts being outputted when Tc represents a natural vibration period of the liquid chambers of the printing head.