Dual frequency switchable cholesteric liquid crystal light shutter and

Abstract

A liquid crystal shutter and a drive waveform for controlling the same is presented by this invention. The liquid crystal shutter includes two distinct layers of liquid crystal material where one layer has a right hand twist sense and the other layer has a left hand twist sense. An electric field is selectively applied to the layers of liquid crystal material which have dual frequency properties. Accordingly, when a low frequency is applied to the liquid crystal materials they exhibit a positive dielectric anisotropy and a homeotropic texture which is substantially transparent. When a high frequency electric field is applied to the liquid crystal materials they exhibit a negative dielectric anisotropy and a planar texture which is substantially reflective. The liquid crystal material may be selected to selectively reflect predetermined spectrums of light. By alternatingly applying low and high frequencies to the liquid crystal shutter, the transition time between the transparent and reflective states is minimized.