Dynamic diffractive liquid crystal lens

1. An ophthalmic apparatus, comprising:

first liquid crystal material enclosed between a first diffractive lens structure and a first substrate surface having a first alignment layer disposed thereon; and

second liquid crystal material enclosed between a second diffractive lens structure and a second substrate surface having a second alignment layer disposed thereon;

wherein the first and second liquid crystal materials assume a homeotropic alignment relative to the first and second substrate surfaces, respectively, in a first mode,

wherein the first alignment layer is configured to align the first liquid crystal material along a first direction and the second alignment layer is configured to align the second liquid crystal material along a second direction, substantially orthogonal to the first direction, in a second mode of the first and second liquid crystal materials,

wherein the first and second diffractive lens structures and the first and second liquid crystal materials form a multi-layer lens stack having a first optical power in the first mode and a second optical power, different from the first optical power, in the second mode,

wherein the first mode that homeotropically aligns the first and second liquid crystal materials comprises a default mode of the ophthalmic apparatus that persists in an absence of applied voltages across both of the first and second liquid crystal materials, and wherein the default mode is configured for distance vision of a wearer of the ophthalmic apparatus, and

wherein the second mode that aligns the first and second liquid crystal materials orthogonal to each other via application of voltages across both the first and second liquid crystal materials is configured for near vision of the wearer of the ophthalmic apparatus.

2. The ophthalmic apparatus of claim 1 , wherein the first and second liquid crystal materials have a first refractive index during the first mode and a second refractive index, different than the first refractive index, during the second mode, for light incident through the multi-layer lens stack along a normal trajectory through the first and second substrate surfaces.

3. The ophthalmic apparatus of claim 2 , wherein the first refractive index of the first and second liquid crystal materials is polarization insensitive along the normal trajectory in the first mode, and wherein the second refractive index of the first and second liquid crystal materials are orthogonally polarization sensitive along the normal trajectory in the second mode.

4. The ophthalmic apparatus of claim 3 , wherein the second refractive index of the first and second liquid crystal materials are collectively polarization insensitive along the normal trajectory in the second mode.

5. The ophthalmic apparatus of claim 2 , wherein the first refractive index is closer to a third refractive index of the first and second diffractive lens structures than the second refractive index, wherein the multi-layer lens stack has less optical power during the first mode than during the second mode.

6. The ophthalmic apparatus of claim 2 , wherein the first refractive index is an ordinary refractive index of the first and second liquid crystal materials and the second refractive index is an extraordinary refractive index of the first and second liquid crystal materials, both as measured along the normal trajectory.

7. The ophthalmic apparatus of claim 1 , further comprising:

a first electrode pair disposed to apply a first voltage across the first liquid crystal material; and

a second electrode pair disposed to apply a second voltage across the second liquid crystal material,

wherein the first mode is triggered by an absence of the first and second voltages and the second mode is triggered by application of the first and second voltages.

8. The ophthalmic apparatus of claim 7 , wherein the ophthalmic apparatus comprises one of a contact lens or an intraocular lens, the ophthalmic apparatus further comprising:

a controller coupled to selectively apply the first and second voltages; and

a power source coupled to power the controller.

9. The ophthalmic apparatus of claim 1 , wherein the first and second substrate surfaces are disposed between the first and second diffractive lens structures.

10. The ophthalmic apparatus of claim 1 , wherein the first and second diffractive lens structures are disposed between the first and second substrate surfaces.

11. The ophthalmic apparatus of claim 1 , wherein first and second diffractive lens structures are formed of clear plastic.

12. The ophthalmic apparatus of claim 1 , diffraction structures have a modulation depth approximately 3.6 um±1.4 um and the first and second liquid crystal materials are each less than 15 um thick.

13. The ophthalmic apparatus of claim 1 , further comprising:

a substrate including at least one of the first substrate surface or the second substrate surface, and wherein a refractive index of the substrate is different than respective refractive indices of the first diffractive lens structure and the second diffractive lens structure.

14. An ophthalmic lens system, comprising:

a diffractive liquid crystal (“LC”) lens including:

first liquid crystal material enclosed between a first diffractive lens structure and a first substrate surface; and

second liquid crystal material enclosed between a second diffractive lens structure and a second substrate surface, wherein the first and second diffractive lens structures and the first and second liquid crystal materials are stacked; and

a controller coupled to the diffractive LC lens, the controller including logic that, when executed by the controller, will cause the ophthalmic lens system to perform operation comprising:

activating a first mode that homeotropically aligns the first and second liquid crystal materials to the first and second substrate surfaces, respectively, to induce a first optical power of the diffractive LC lens, wherein the first mode that homeotropically aligns both the first and second liquid crystal materials comprises a default mode of the diffractive LC lens that persists in an absence of applied voltages across both of the first and second liquid crystal materials, and wherein the default mode that persists in the absence of applied voltages across both of the first and second liquid crystal materials configures the diffractive LC lens for distance vision; and

activating a second mode that aligns the first liquid crystal material along a first direction and aligns the second liquid crystal material along a second direction, substantially orthogonal to the first direction, to induce a second optical power of the diffractive LC lens, different from the first optical power.

15. The ophthalmic lens system of claim 14 , further comprising:

a first alignment layer disposed across the first substrate surface, the first alignment layer configured to cause the first liquid crystal material to align along the first direction upon activating the second mode; and

a second alignment layer disposed across the second substrate surface, the second alignment layer configured to cause the second liquid crystal material to align along the second direction upon activating the second mode.

16. The ophthalmic lens system of claim 14 , wherein the first and second liquid crystal materials have a first refractive index during the first mode and a second refractive index, different than the first refractive index, during the second mode, for light incident through the diffractive LC lens along a normal trajectory through the first and second substrate surfaces.

17. The ophthalmic lens system of claim 16 , wherein the first refractive index of the first and second liquid crystal materials is polarization insensitive along the normal trajectory in the first mode, and wherein the second refractive index of the first and second liquid crystal materials are orthogonally polarization sensitive along the normal trajectory in the second mode.

18. The ophthalmic lens system of claim 17 , wherein the second refractive index of the first and second liquid crystal materials are collectively polarization insensitive along the normal trajectory in the second mode.

19. The ophthalmic lens system of claim 16 , wherein the first refractive index is closer to a third refractive index of the first and second diffractive lens structures than the second refractive index, wherein the diffractive LC lens has less optical power during the first mode than during the second mode.

20. The ophthalmic lens system of claim 14 , further comprising:

a first electrode pair disposed to apply a first voltage across the first liquid crystal material; and

a second electrode pair disposed to apply a second voltage across the second liquid crystal material,

wherein the first mode comprises the default mode without application of the first and second voltages and the second mode comprises application of the first and second voltages.

21. The ophthalmic lens system of claim 20 , wherein the first and second electrode pairs share a common ground.

22. The ophthalmic lens system of claim 14 ,

wherein the second optical power of the second mode which requires applied voltages across both the first and second liquid crystal materials configures the diffractive LC lens for near vision.

23. An ophthalmic apparatus, comprising:

first liquid crystal material enclosed between a first diffractive lens structure and a first substrate surface having a first alignment layer disposed thereon; and

second liquid crystal material enclosed between a second diffractive lens structure and a second substrate surface having a second alignment layer disposed thereon;

wherein the first liquid crystal material, the second liquid crystal material, the first diffractive lens structure, and the second diffractive lens structure are arranged to form a multi-layer lens stack with variable optical power including a first optical power for distance vision corresponding to a first mode and a second optical power for near vision corresponding to a second mode,

wherein during the first mode the first optical power for distance vision is provided, at least in part, by a homeotropic alignment of the first and second liquid crystal materials that persists in an absence of applied voltages across the first and second liquid crystal materials; and

wherein during the second mode the second optical power for near vision is provided, at least in part, by application of voltages across the first and second liquid crystal materials to align the first and second liquid crystal materials substantially orthogonal to each other.