Optical waveguide for directional backlight

A backlight apparatus comprising:

• an optical waveguide comprising:
• first and second opposed light guiding surfaces for guiding light along the optical waveguide by total internal reflection,
• a first light input end arranged between the first and second light guiding surfaces, wherein the first light input end extends in a lateral direction, and
• a second light input end arranged between the first and second light guiding surfaces, wherein the second light input end extends in a lateral direction facing the first light input end;
• at least one light source arranged to input light into the optical waveguide at the first input end;
• and
• at least one further light source arranged to input light into the optical waveguide at the second input end,
• wherein the second light guiding surface of the optical waveguide comprises:
• (i) a plurality of non-inclined light extraction features arranged in a two dimensional array, each non-inclined light extraction feature being elongate, extending in a longitudinal direction perpendicular to the lateral direction, and having surface normal directions that vary in a plane orthogonal to the longitudinal direction and that have no component of tilt in the longitudinal direction;
• and
• (ii) a plurality of inclined light extraction features arranged in a two dimensional array, each inclined light extraction feature having a surface normal direction with a tilt that has a component in the longitudinal direction,
• the plurality of non-inclined light extraction features and the plurality of inclined light extraction features being oriented to direct guided light through the first and second light guiding surfaces as output light having different angular illumination profiles for light input through the first and second input ends.