Abstract: A display 17 comprises a display panel 2 and a backlighting system comprising a light source 3 and waveguide 18. The waveguide 18 comprises a plurality of portions of diffusing material 10a to 10f. Light propagates through the waveguide 18 by means of total internal reflection, but may be scattered by a portion 10a to 10f. Scattered light leaving the waveguide 18 through its exit face 15 produces a pattern of light lines for use in illuminating a 3D autostereoscopic image displayed by the display panel 2. Intervening portions 19a to 19f may be provided, formed from a material such as a liquid crystal gel that can be switched between a light transmissive state and a diffusive state. Optical properties of the intervening portions 19a to 19f may be controlled using electric fields.