A waveform forming device comprises a light source, a liquid crystal light shutter for passing or preventing the light of the light source and a driving circuit for driving a plurality of electrodes of the liquid crystal light shutter by using drive control signals including a signal of a high frequency f.sub.H and a signal of a low frequency f.sub.L. The frequencies f.sub.H and f.sub.L are respectively higher and lower than the frequency which makes a liquid crystal dielectric anisotropy zero. The waveform forming device has a ROM in which a plurality of basic control signals are stored, a counter for addressing a desired memory areas of the ROM and a waveform selector for selecting the basic control signals. The drive control signals are formed by combining the basic control signals, thereby to provide a desired drive pattern signal.