A display device comprising: a backlight arranged to output light, the backlight comprising a directional waveguide ; and plural light sources arranged to input input light into the waveguide , the waveguide being arranged to direct light from different light sources into different solid angular extents as the output light; a transmissive spatial light modulator arranged to receive the output light from the backlight ; an input polariser arranged on the input side of the spatial light modulator between the backlight and the spatial light modulator ; and an output polariser arranged on the output side of the spatial light modulator , characterised by further comprising: an additional polariser arranged on the input side of the input polariser between the input polariser and the backlight or on the output side of the output polariser ; and a switchable liquid crystal retarder comprising a layer of liquid crystal material arranged between the at least one additional polariser and the input polariser in the case that the additional polariser is arranged on the input side of the input polariser or between the additional polariser and the output polariser in the case that the additional polariser is arranged on the output side of the output polariser ; and a control system arranged to synchronously control the light sources and the at least one switchable liquid crystal retarder . a backlight arranged to output light, the backlight comprising a directional waveguide ; and plural light sources arranged to input input light into the waveguide , the waveguide being arranged to direct light from different light sources into different solid angular extents as the output light; a transmissive spatial light modulator arranged to receive the output light from the backlight ; an input polariser arranged on the input side of the spatial light modulator between the backlight and the spatial light modulator ; and an output polariser arranged on the output side of the spatial light modulator , characterised by further comprising: an additional polariser arranged on the input side of the input polariser between the input polariser and the backlight or on the output side of the output polariser ; and a switchable liquid crystal retarder comprising a layer of liquid crystal material arranged between the at least one additional polariser and the input polariser in the case that the additional polariser is arranged on the input side of the input polariser or between the additional polariser and the output polariser in the case that the additional polariser is arranged on the output side of the output polariser ; and a control system arranged to synchronously control the light sources and the at least one switchable liquid crystal retarder . an additional polariser arranged on the input side of the input polariser between the input polariser and the backlight or on the output side of the output polariser ; and a switchable liquid crystal retarder comprising a layer of liquid crystal material arranged between the at least one additional polariser and the input polariser in the case that the additional polariser is arranged on the input side of the input polariser or between the additional polariser and the output polariser in the case that the additional polariser is arranged on the output side of the output polariser ; and a control system arranged to synchronously control the light sources and the at least one switchable liquid crystal retarder . <EOS>