The diffraction grating principle is used to deflect an infrared beam in a series of discrete predetermined directions. A periodic control voltage having a staircase waveform with N steps is applied across a liquid crystal layer to create local variations of refractive index therein, thereby setting...http://www.google.com.au/patents/US4639091?utm_source=gb-gplus-sharePatent US4639091 - Static deflector device for an infrared beam
