A directional backlight comprising: a waveguide ; an array of light sources arranged to input input light into the waveguide at different input positions laterally across the waveguide , wherein the waveguide comprises first and second, opposed guide surfaces for guiding input light along the waveguide , the first guide surface being arranged to guide light by total internal reflection, and the second guide surface comprising: (a) a plurality of extraction features that are (i) arranged to reflect some of the input light so as to output it from the waveguide through the first guide surface and (ii) laterally curved to have positive optical power laterally so that the input light reflected from the extraction features laterally forms real images of the light sources in front of the directional backlight in a first window plane that provide viewing windows, the extraction features also transmitting some of the input light; and (b) intermediate regions between the extraction features that are arranged to guide light by total internal reflection; and a rear reflector comprising a linear array of reflective facets that are (i) arranged to reflect at least some of the input light that is transmitted through the extraction features of the waveguide , so as to direct it back through the waveguide to exit through the first guide surface , and (ii) laterally curved to have optical power laterally, characterised in that the linear array of reflective facets of the rear reflector are arranged so that the input light reflected from the reflective facets laterally forms images of the light sources in a second window plane that is separated from the first window plane. a waveguide ; an array of light sources arranged to input input light into the waveguide at different input positions laterally across the waveguide , wherein the waveguide comprises first and second, opposed guide surfaces for guiding input light along the waveguide , the first guide surface being arranged to guide light by total internal reflection, and the second guide surface comprising: (a) a plurality of extraction features that are (i) arranged to reflect some of the input light so as to output it from the waveguide through the first guide surface and (ii) laterally curved to have positive optical power laterally so that the input light reflected from the extraction features laterally forms real images of the light sources in front of the directional backlight in a first window plane that provide viewing windows, the extraction features also transmitting some of the input light; and (b) intermediate regions between the extraction features that are arranged to guide light by total internal reflection; and a rear reflector comprising a linear array of reflective facets that are (i) arranged to reflect at least some of the input light that is transmitted through the extraction features of the waveguide , so as to direct it back through the waveguide to exit through the first guide surface , and (ii) laterally curved to have optical power laterally, characterised in that the linear array of reflective facets of the rear reflector are arranged so that the input light reflected from the reflective facets laterally forms images of the light sources in a second window plane that is separated from the first window plane. <EOS>