CPC G02B 27/0179 (2013.01) [G02B 26/0833 (2013.01); G02B 27/0093 (2013.01); G02B 27/0172 (2013.01); G02B 27/286 (2013.01); G02B 2027/0174 (2013.01); G02B 2027/0187 (2013.01)] | 17 Claims |
1. A directional illuminator for a display panel, the directional illuminator comprising:
a light source for providing a light beam;
a pupil-replicating lightguide; and
a tiltable reflector for receiving the light beam from the light source and redirecting the light beam towards the pupil-replicating lightguide at a variable incidence angle;
wherein the pupil-replicating lightguide is configured to propagate the light beam therein by reflection from opposed surfaces of the pupil-replicating lightguide;
the pupil-replicating lightguide comprising a polarization-selective out-coupling grating for propagating light at a first polarization therethrough substantially without changing direction of propagation and for out-coupling light at a second, orthogonal polarization state from the pupil-replicating lightguide, such that offset parallel portions of the light beam at the second polarization state are out-coupled along at least one of the opposed surfaces at a variable out-coupling angle corresponding to the variable incidence angle of the light beam;
the directional illuminator further comprising an array of tunable polarization rotators optically coupled to the pupil-replicating lightguide along at least one of its opposed surfaces and configured to tune a polarization state of the light beam propagating in the pupil-replicating lightguide in a spatially-selective manner.
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