TUNABLE LIQUID CRYSTAL OPTICAL DEVICE
A liquid crystal optical device has a layered structure with split liquid crystal layers having alignment surfaces that define in a liquid crystal material pre-tilt angles of opposite signs. Four liquid crystal layers can provide two directions of linear polarization. In the case of a lens, the device can be a gradient index lens, and the alignment surfaces can have a spatially uniform pre-tilt.
1 . A liquid crystal lens device having a layered structure, the device comprising:
split liquid crystal cells each having an alignment surface that defines in a liquid crystal material a pre-tilt angle of opposite signs wherein said split liquid crystal cells comprise a middle separation substrate that has surfaces that define a direction of ordering of the liquid crystal without defining a pre-tilt angle; and
electrodes configured to generate an electric field that controls an orientation of said liquid crystal material, wherein the electric field influences the liquid crystal material in the split liquid crystal cells such that a combined effect of the split liquid crystal cells on a propagation of light incident on the lens is substantially the same, independent of an angle of incidence of the light on the lens.
2 . The device as defined in claim 1 , wherein the split liquid cells form a first split cell pair and both cells of the pair act primarily on a first linear polarization of light, and wherein the device further comprises a second split cell pair comprising split cells, both cells of which act primarily on a second linear polarization of light essentially orthogonal to linear polarizations of light.
3 . The device as defined in claim 1 , wherein said pre-tilt is spatially uniform.
4 . The device as defined in claim 1 , wherein said device is a gradient index lens.
5 . The device as defined in claim 1 , wherein said electrodes are planar electrodes.
6 . The device as defined in claim 5 , wherein said electric field is spatially modulated using a layer of essentially uniform index of refraction and spatially non-uniform dielectric constant.
7 . The device as defined in claim 5 , wherein one of said electrodes is patterned and said electric field is spatially modulated using a layer of complex dielectric material associated with said patterned electrode to shape said electric field as a function of control signal frequency.
8 . The device as defined in claim 7 , wherein said one electrode is a middle electrode operating between opposed planar electrodes defining separately an electric field on each side of said one electrode.
9 . The device as defined in claim 8 , wherein said middle electrode is deposited on a surface of a first thin rigid substrate with a second thin rigid substrate bonded over said middle electrode, wherein said alignment surfaces can be arranged on outer surfaces of said middle electrode.
10 . (canceled)
11 . The device as defined in claim 9 , wherein said middle separation substrate comprises a sheet of material stretched in said direction of ordering.
12 . The device as defined in claim 11 , wherein said sheet of material is made of polyimide.
13 . The device as defined in claim 12 , wherein said sheet is less than 60 microns thick.
14 . A tunable liquid crystal optical device having a layered structure, the device comprising:
two identical layered liquid crystal optical devices each acting on a direction of polarization, made a number at a time by a wafer process and singulated, joined together after a 90 degree rotation, wherein each one of said two identical layered liquid crystal optical devices operates primarily on a different one of two perpendicular polarizations of light.
15 . The device as claimed in claim 14 , wherein said identical layered liquid crystal optical devices comprise split liquid crystal cells having pre-tilt angles of opposite signs.
16 . The device as claimed in claim 14 , wherein said device is a variable focus lens.
17 . The device as claimed in claim 14 , wherein the two identical layered liquid crystal optical devices are joined together after a 90 degree rotation and flip.
18 . The device as defined in claim 13 , wherein:
the split liquid cells form a first split cell pair and both cells of the pair act primarily on a first linear polarization of light,
the device further comprises a second split cell pair comprising split cells both cells of which act primarily on a second linear polarization of light essentially orthogonal to linear polarizations of light,
said pre-tilt is spatially uniform,
said device is a gradient index lens, and
said sheet is less about 20 microns thick.
19 . The device as defined in claim 6 , wherein:
the split liquid cells form a first split cell pair and both cells of the pair act primarily on a first linear polarization of light,
the device further comprises a second split cell pair comprising split cells both cells of which act primarily on a second linear polarization of light essentially orthogonal to linear polarizations of light,
said pre-tilt is spatially uniform, and
said device is a gradient index lens.
20 . The device as defined in claim 1 , wherein said middle separation substrate comprises a sheet of material stretched in said direction of ordering.
21 . The device as defined in claim 20 , wherein said sheet of material is made of polyimide and said sheet is less than 60 microns thick.