| 摘要 |
PURPOSE:To sufficiently illuminate a liquid crystal optical element and to obtain excellent temperature characteristics by repeatedly impressing a high frequency electric field to a liquid crystal material during a writing period and impressing a low frequency electric field during one period in the repeated high frequency field impressing period. CONSTITUTION:A selecting period T1 consists of periods T3-T6, and in the case of an ON signal, a high frequency field fHL is impressed to the periods T3, T5, a low frequency field fL for temporarily turning off a shutter is impressed to the period T4 and a superposed electric field fHL for holding the ON state is impressed to the period T5. When the high frequency field is repeatedly impressed and the low frequency field is impressed during the period, a liquid crystal shutter is repeatedly turned on and off. Consequently, the total ON period is prolonged and the quantity of light is increased, and since the low frequency field is impressed in a short period, the influence of a hysteresis effect based upon the high frequency field is reduced and the temperature characteristics can be improved.
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