Patent ID: 8004621

Claim:
A display apparatus comprising: a display device comprising: a spatial light modulator; and an output polariser; and an electrically switchable birefringent lens array positioned between the spatial light modulator and the output polariser of the display device, wherein the lens array comprises: birefringent material arranged between a planar surface and a relief surface defining an array of cylindrical lenses; and electrodes for applying a control voltage across the birefringent material for electrically switching the birefringent material between a first mode and a second mode, the lens array being arranged in said first mode to modify the directional distribution of incident light polarised in a predetermined direction and in said second mode to have substantially no effect on incident light polarised in said predetermined direction, wherein: in the first mode, at said relief surface the birefringent material is aligned substantially parallel to a geometrical axis of the cylindrical lenses; and in the first mode, at said planar surface the birefringent material is aligned parallel to the planar surface at a predetermined angle such that, in the first mode, the alignment direction twists between the planar surface and the relief surface.