US Patent 11099433 Switchable directional display apparatus

A switchable directional display apparatus comprises a spatial light modulator and a backlight comprising a waveguide, two light sources arranged to provide illumination through the edge of the waveguide and a switchable liquid crystal retarder. The light sources and switchable liquid crystal retarder may be controlled to provide a first operating state with a narrow field of view and a second operating state with a wide field of view. Image visibility in wide angle mode of operation may be maximised while visual security level may be maximised in a narrow angle mode of operation, to provide an efficient privacy mode of operation.