Light input for directional backlight

A directional backlight comprising:

• a waveguide comprising first and second, opposed guide surfaces for guiding input light along the waveguide, wherein the second guide surface comprises at least two parts each extending partway along the waveguide, being separated perpendicular to the lateral direction by an input aperture;
• and
• an array of light sources arranged to generate input light and to inject the input light through the input aperture into the waveguide at respective input positions in a lateral direction across the waveguide, wherein
• the waveguide further comprises a reflective end arranged to reflect the input light back through the waveguide to each of the parts of the second guide surface,
• the first guide surface is arranged to guide light by total internal reflection, each of parts of the second guide surface comprises a plurality of light extraction features that extend linearly and parallel to each other and intermediate regions between the light extraction features that are arranged to direct light through the waveguide without extracting it, the light extraction features being oriented to deflect the input light after reflection from the reflective end in directions allowing exit through the first guide surface as output light through the first guide surface, and
• the reflective end has positive optical power in the lateral direction so that the waveguide directs the output light from the light sources into optical windows in output directions that are positioned in a lateral direction in dependence on the input position of the input light.