Wide field-of-view polarization switches and methods of fabricating liquid crystal optical elements with pretilt
A switchable optical assembly comprises a switchable waveplate configured to be electrically activated and deactivated to selectively alter the polarization state of light incident thereon. The switchable waveplate comprises first and second surfaces and a first liquid crystal layer disposed between the first and second surfaces. The first liquid crystal layer comprises a plurality of liquid crystal molecules that are rotated about respective axes parallel to a central axis, where the rotation varies with an azimuthal angle about the central axis. The switchable waveplate additionally comprises a plurality of electrodes to apply an electrical signal across the first liquid crystal layer.
1 . A switchable optical assembly comprising:
a switchable waveplate configured to be electrically activated and deactivated to selectively alter the polarization state of light incident thereon, said switchable waveplate comprising:
first and second surfaces;
a liquid crystal layer disposed between said first and second surfaces, said liquid crystal layer comprising a plurality of liquid crystal molecules that are longer than wide along respective longitudinal directions, said liquid crystal molecules orientated such that said longitudinal directions extend radially from an axis of said first and second surfaces and said liquid crystal layer in a plurality of radial directions from said axis; and
a first electrode layer and a second electrode layer arranged on either side of the liquid crystal layer and configured to apply an electrical signal across said liquid crystal layer,
wherein the first electrode layer includes a pattern of nanostructures formed as part of the first electrode layer, and wherein the pattern of nanostructures is configured to align the liquid crystal molecules of the liquid crystal layer to the pattern when the electrical signal is not applied.
2 . The switchable optical assembly of claim 1 , wherein the first and second surfaces comprise planar surfaces.
3 . The switchable optical assembly of claim 1 , wherein the first and second surfaces comprise planar surfaces on planar substrates.
4 . The switchable optical assembly of claim 1 , wherein the axis is normal to said first and second surfaces.
5 . The switchable optical assembly of claim 1 , wherein said plurality of liquid crystal molecules are rotated about axes parallel to said axis.
6 . The switchable optical assembly of claim 1 , wherein said longitudinal directions of said liquid crystal molecules are parallel to said first and second surfaces.
7 . The switchable optical assembly of claim 1 , configured to transmit light to a viewer's eye at a distance from said switchable optical assembly, wherein said longitudinal directions of said liquid crystal molecules extend along respective projections of a path of light from respective locations in a field of view of the viewer's eye to the viewer's eye that are projected onto the liquid crystal layer.
8 . The switchable optical assembly of claim 1 , further comprising a waveplate lens comprising a diffractive lens.
9 . The switchable optical assembly of claim 1 , further comprising a waveplate lens comprising a liquid crystal layer, wherein the liquid crystal layer of the waveplate lens is arranged such that the waveplate lens has birefringence that varies in a radially outward direction from a central region of the waveplate lens.
10 . The switchable optical assembly of claim 1 , wherein when the switchable waveplate is in a first state, the switchable waveplate serves as a half waveplate configured to invert a handedness of circularly polarized light passing therethrough, while when the switchable waveplate is in a second state, the switchable waveplate is configured to conserve the handedness of circularly polarized light passing therethrough.
11 . The switchable optical assembly of claim 1 , wherein the liquid crystal layer comprises a plurality of sublayers and said liquid crystal molecules are included in a first sublayer of the plurality of sublayers.
12 . The switchable optical assembly of claim 11 , wherein said plurality of sublayers includes additional sublayers having liquid crystal molecules oriented and positioned the same laterally or radially as the liquid crystal molecules included in the first sublayer.
13 . The switchable optical assembly of claim 1 , wherein the switchable optical assembly further comprises a waveplate lens comprising a liquid crystal layer, said waveplate lens having different optical power for different polarizations of light incident thereon, and
wherein the switchable optical assembly is configured to be selectively switched between at least two lens states including:
a first lens state configured to have a first optical power; and
a second lens state configured to have a second optical power different than the first optical power.
14 . The switchable optical assembly of claim 13 , wherein the second optical power is zero optical power.
15 . The switchable optical assembly of claim 1 , wherein the plurality of liquid crystal molecules orientated such that said respective longitudinal directions extend radially from said axis in a plurality of radial directions from said axis include at least 50% of liquid crystal molecules extending over a range of at least 1 cm 2 across said liquid crystal layer.
16 . The switchable optical assembly of claim 1 , wherein the plurality of liquid crystal molecules orientated such that said respective longitudinal directions extend radially from said axis in a plurality of radial directions from said axis include at least 50% of liquid crystal molecules extending over a range of at least 2 cm 2 across said liquid crystal layer.
17 . The switchable optical assembly of claim 1 , wherein the plurality of liquid crystal molecules orientated such that said respective longitudinal directions extend radially from said axis in a plurality of radial directions from said axis include at least 80% of liquid crystal molecules extending over a range of at least 1 cm 2 across said liquid crystal layer.
18 . The switchable optical assembly of claim 1 , wherein the plurality of liquid crystal molecules orientated such that said respective longitudinal directions extend radially from said axis in a plurality of radial directions from said axis include at least 80% of liquid crystal molecules extending over a range of at least 2 cm 2 across said liquid crystal layer.
19 . The switchable optical assembly of claim 1 , wherein said axis comprises a central axis of said first and second surfaces and said liquid crystal layer.
20 . The switchable optical assembly of claim 1 , wherein the nanostructures are nanowires.