A display apparatus has a switchable birefringent lens array. The display apparatus produces a substantially linearly polarized output. The lens array comprises birefringent material arranged between a planar surface of a first substrate and a relief substrate of a second substrate defining an array of cylindrical lenses. The lens array has electrodes for applying a control voltage across the birefringent material for electrically switching the birefringent material between a first mode and a second mode. In the first mode the lens array modifies the directional distribution of incident light polarized in a predetermined direction. In the second mode the lens array has substantially no effect on incident light polarized in said predetermined direction. In a first aspect, in the first mode, at said relief surface the birefringent material is aligned substantially parallel to the geometrical axis of the cylindrical lenses, and at said planar surface the birefringent material is aligned parallel to the planar surface at a predetermined angle such that the alignment direction twists between the planar surface and the relief surface. In a second aspect, the birefringent material is homeotropically aligned at said at least one relief surface. In a third aspect, the lens array is arranged between a spatial light modulator and the output polarizer of the display device. In a fourth aspect, the lens array receives light from an emissive spatial light modulator which is arranged to output light which is substantially linearly polarized in each pixel. In a fifth aspect a voltage controller controls the voltage across the electrodes to switch between the first and second modes so as to compensate for variations in the temperature of the lens array apparatus, whereby the operating temperature range can be extended.