Abstract: There is disclosed herein a display device comprising a picture generating unit, a waveguide pupil expander and a viewer-tracking system. The picture generating unit comprises a first display channel, a second display channel and a controller. The first display channel is arranged to output first spatially-modulated light of a first colour. The first spatially-modulated light corresponds to a first picture. The second display channel is arranged to output second spatially-modulated light of a second colour. The second spatially-modulated light corresponding to a second picture. The controller is arranged to drive the first display channel and second display channel. The waveguide pupil expander comprises a pair of parallel reflective surfaces. The waveguide pupil expander defines an input port and a viewing window. The input port is arranged to receive the first spatially-modulated light and the second spatially-modulated light.