Patent ID: 7355952

Claim:
A method for driving a liquid crystal device including a first transparent substrate and a second transparent substrate that face each other, a liquid crystal filled between the first and second transparent substrates, a first transparent electrode formed on a surface of the first transparent substrate that faces the second transparent substrate, and a second transparent electrode formed on a surface of the second transparent substrate that faces the first transparent substrate, the method comprising the steps of: applying a first driving signal of a square-wave voltage to the first transparent electrode and applying a second driving signal of a square-wave voltage to the second transparent electrode; where the first driving signal has a voltage amplitude V 1 , a frequency F 1 , and a duty ratio D 1 , the second driving signal has a voltage amplitude V 2 , a frequency F 2 , and a duty ratio D 2 , and a phase difference between the first driving signal and the second driving signal is indicated by Ï†, adjusting V 1 and V 2 so that a refractive index Î”N of the liquid crystal changes in a substantially linear range relative to Ï†; and controlling the refractive index Î”N of the liquid crystal by adjusting the phase difference Ï† in a state where V 1 =V 2 , F 1 =F 2 , and D 1 =D 2 so as to vary an effective voltage to be applied to the liquid crystal.