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 gradient index optical lens device having a layered structure, the device comprising:
four liquid crystal layers in split liquid crystal cells for acting on essentially orthogonal linear polarizations of light, each liquid crystal cell having an alignment surface that defines in a liquid crystal material a spatially uniform pre-tilt angle of opposite signs; and
planar electrodes for generating an electric field controlling an orientation of said liquid crystal material, wherein one of said electrodes being 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, 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, wherein said liquid crystal optical device has angular symmetry of optical power.
2. The device as defined in claim 1 , 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.
3. A liquid crystal optical 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; and
electrodes for generating an electric field controlling an orientation of said liquid crystal material, 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 wherein said liquid crystal optical device has angular symmetry of optical power.
4. The device as defined in claim 3 , wherein said middle separation substrate comprises a sheet of material stretched in said direction of ordering.
5. The device as defined in claim 4 , wherein said sheet of material is made of polyimide.
6. The device as defined in claim 3 , comprising four liquid crystal cells for acting on essentially orthogonal linear polarizations of light.
7. The device as defined in claim 6 , wherein said pre-tilt is spatially uniform.
8. The device as defined in claim 7 , wherein said device is a gradient index lens.
9. The device as defined in claim 8 , wherein said electrodes are planar electrodes with one of said electrodes being 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.