Display apparatus
A display apparatus comprises a spatial light modulator and optical elements in series therewith. The optical elements provide a first parallax element being a parallax barrier capable of directing light output from the display apparatus into a first plurality of viewing windows, and a second parallax element capable of directing light output from the display apparatus into a second plurality of viewing windows. In a first mode, the first and second parallax elements have substantially no directional effect on the light output from the display apparatus. In a second mode, the first parallax element directs light output from the display apparatus into the first plurality of viewing windows and the second optical element has substantially no directional effect. In a third mode, the second optical element directs light output from the display apparatus into the second plurality of viewing windows and the first parallax element has substantially no directional effect.
1. A display apparatus comprising:
a spatial light modulator; and
a birefringent lens array arranged in series with the spatial light modulator and comprising a layer of birefringent material between two opposing lens surfaces, the lens surfaces each shaped as an array of cylindrical lenses extending substantially orthogonally to each other,
the display apparatus being switchable between a first mode in which the birefringent lens array has substantially no directional effect on light output from the display apparatus and a second mode in which the directional distribution of the light output from the display apparatus is modified by both of the opposing lens surfaces.
2. A display apparatus according to claim 1 , wherein the birefringent lens array is an active birefringent lens array comprising electrodes for applying an electric field across the layer of birefringent material, the display apparatus being switchable between the first and second modes by switching of the voltage applied across said electrodes.
3. A display apparatus according to claim 1 , wherein the birefringent lens array is a passive birefringent lens array and the display apparatus further comprises a switchable polarisation control device arranged in series with the birefringent lens array which is switchable to pass light of either a first polarisation component or a second polarisation component, the birefringent lens array having substantially no directional effect on light of the first polarisation component and modifying the directional distribution of light of the second polarisation component, the display apparatus being switchable between the first and second modes by switching of the switchable polarisation control device.
4. A display apparatus according to claim 1 , wherein the two opposing lens surfaces are formed as the surfaces of two respective layers of material, which layers of material are provided outside the lens surfaces with alignment features which engage each other to align the lens surfaces relative to each other.
5. A display apparatus according to claim 1 , wherein the display apparatus is an autostereoscopic display apparatus and the cylindrical lenses are for directing light from the spatial light modulator into a plurality of viewing windows.