Switchable holographic device

摘要

A switchable holographic diffraction device comprises holographic fringes (14) formed by liquid crystal droplets (15) dispersed in a medium. The droplets are composed of at least partly of a non-nematic (preferably cholesteric) liquid crystal material. The fringes are switchable between a first condition in which the liquid crystal molecules are oriented randomly with respect to a direction of propagation of radiation through the device (Figure 3), and a second condition in which the liquid crystal molecules are oriented uniformly with respect to said direction of radiation propagation (Figure 4).