Adaptive lens assemblies including polarization-selective lens stacks for augmented reality display
The present disclosure relates to display systems and, more particularly, to augmented reality display systems an related methods. In one aspect, an adaptive lens assembly includes a lens stack configured to exert polarization-dependent optical power to linearly polarized light. The lens stack includes a birefringent lens and an isotropic lens contacting each other to form a conformal interface therebetween. The adaptive lens assembly is configured to be selectively switched between a plurality of states having different optical powers.
1. A method comprising:
focusing, via an adaptive lens assembly of a head mounted augmented reality display device, virtual images at a plurality of depth planes among a real world view,
wherein the adaptive lens assembly comprises a lens stack supported by the head mounted augmented reality display device and is configured to exert polarization-dependent optical power to linearly polarized light,
wherein the lens stack comprises a birefringent lens and an isotropic lens contacting each other to form a conformal interface therebetween, and
wherein the focusing includes selectively switching the adaptive lens assembly between a plurality of states having different optical powers to focus the virtual images at the plurality of plane depths among the real world view while simultaneously refocusing the real world view to appear without substantial distortion.
2. The method of claim 1 , wherein the birefringent lens has an optic axis and a birefringence (Δn) and is configured to exert a first optical power to light having a polarization direction parallel to the optic axis, and to exert a second optical power to light having a polarization direction perpendicular to the optic axis; and
wherein the isotropic lens has a refractive index and is configured to exert to light passing therethrough a third optical power opposite in sign as the first optical power and the second optical power.
3. The method of claim 2 , wherein the Δn corresponds to a difference between an extraordinary refractive index (ne) in a direction parallel to the optic axis of the birefringent lens and an ordinary refractive index (no) in a direction perpendicular to the optic axis of the birefringent lens, and wherein the refractive index of the isotropic lens has substantially the same value as the no of the birefringent lens.
4. The method of claim 2 , wherein the third optical power is substantially the same in magnitude as the second optical power, such that the lens stack is configured to exert substantially no optical power to light having a polarization direction perpendicular to the optic axis.
5. The method of claim 2 , wherein the lens stack is configured to exert an optical power proportional to the Δn to light having a polarization direction parallel to the optic axis.
6. The method of claim 1 , wherein the adaptive lens assembly further comprises a switchable half waveplate comprising twisted nematic (TN) liquid crystals (LCs) optically coupled to the lens stack, and wherein the focusing includes preserving, via the switchable half waveplate, a polarization of linear polarized light passing therethrough when activated and altering, via the switchable half waveplate, the polarization of linear polarized light passing therethrough when deactivated.
7. The method of claim 6 , wherein the switchable half waveplate is disposed on a first side of the lens stack, wherein the adaptive lens assembly further comprises on a second side of the lens stack:
a second switchable half waveplate comprising TN LCs optically coupled to the lens stack; and
a second lens stack configured to exert polarization-dependent optical power to linearly polarized light, wherein the second lens stack comprises a second birefringent lens and a second isotropic lens contacting each other to form a conformal interface therebetween, and
wherein the focusing includes selectively switching the adaptive lens assembly between at least four states by electrically activating and/or deactivating the switchable half waveplate and/or the second switchable half waveplate.
8. The method of claim 1 , wherein the birefringent lens comprises reactive mesogens, and wherein the lens stack comprises electrodes configured to apply an electric field across the birefringent lens such that the lens stack is configured to be electrically switchable between different optical power states.
9. A method comprising:
focusing, via a head mounted augmented reality display device, virtual images at a plurality of depth planes among a real world view, the focusing including:
guiding, via a waveguide assembly, light in a lateral direction parallel to an output surface of the waveguide assembly,
outcoupling, via the waveguide assembly, the guided light through the output surface; and
receiving, via an adaptive lens assembly disposed on a first side of the waveguide assembly, outcoupled light from the waveguide assembly, and
selectively switching the adaptive lens assembly between a plurality of states having different optical powers to focus the virtual images at the plurality of plane depths among the real world view while simultaneously refocusing the real world view to appear without substantial distortion,
wherein the adaptive lens assembly comprises a lens stack configured to exert polarization-dependent optical power to linearly polarized light, the lens stack comprising a birefringent lens and an isotropic lens contacting each other, and wherein contacting surfaces of the birefringent lens and the isotropic lens form a conformal interface.
10. The method of claim 9 , wherein:
the birefringent lens has an optical axis and a birefringence (Δn) and is configured to exert a first optical power to light having a polarization direction parallel to the optic axis, and to exert a second optical power to light having a polarization direction perpendicular to the optic axis, and
the isotropic lens has a refractive index and is configured to exert to light passing therethrough a third optical power opposite in sign as at least one of the first optical power and the second optical power.
11. The method of claim 9 , further comprising:
a second adaptive lens assembly disposed on a second side of the waveguide assembly opposite the first side, the second adaptive lens assembly configured to be selectively switched between a plurality of states having different optical powers and comprising:
a second lens stack configured to exert polarization-dependent optical power to linearly polarized light, wherein the second lens stack comprises a second birefringent lens and a second isotropic lens contacting each other to form a conformal interface therebetween.
12. The method of claim 11 , wherein each of the first and second adaptive lens assemblies further comprises a switchable half waveplate comprising twisted nematic (TN) liquid crystals (LCs) optically coupled to a respective one of the lens stack or the second lens stack, and wherein the focusing includes preserving, via the switchable half waveplate, a polarization of linear polarized light passing therethrough when activated and altering, via the switchable half waveplate, the polarization of linear polarized light passing therethrough when deactivated.
13. The method of claim 12 , wherein each of the plurality of optical powers exerted by the second adaptive lens assembly has a corresponding one of the plurality of optical powers exerted by the adaptive lens assembly having substantially the same magnitude and having an opposite sign.
14. The method of claim 11 , wherein each of the birefringent lens and the second birefringent lens comprises reactive mesogens, and wherein each of the lens stack and the second lens stack comprises electrodes configured to switch the each of the lens stack and the second lens stack between different optical power states.
15. The method of claim 9 , wherein the birefringent lens comprises reactive mesogens, and wherein the lens stack comprises electrodes for electrically switching the lens stack between at least two optical power states.
16. A method comprising:
focusing, via a head mounted augmented reality display device, virtual images at a plurality of depth planes among a real world view, the focusing including:
guiding, via a waveguide assembly, light in a lateral direction parallel to an output surface of the waveguide assembly,
outcoupling, via the waveguide assembly, the guided light through the output surface; and
receiving, via an adaptive lens assembly disposed on a first side of the waveguide assembly, outcoupled light from the waveguide assembly, and
selectively switching the adaptive lens assembly between a plurality of states having different optical powers to focus the virtual images at the plurality of plane depths among the real world view while simultaneously refocusing the real world view to appear without substantial distortion,
wherein the adaptive lens assembly is formed on a first side of the waveguide assembly, wherein the display device further comprises a polarizing reflector interposed between the waveguide assembly and adaptive lens assembly, and wherein the polarizing reflector is configured to pass therethrough linear polarized light having a first polarization to reflect linear polarized light having a second polarization.
17. The method of claim 16 , further comprising on a second side of the waveguide assembly a nonpolarizing reflector and a quarter waveplate interposed between the nonpolarizing reflector and the waveguide assembly, wherein the nonpolarizing reflector is configured to reflect and to alter the polarization of linear polarized light having the first polarization incident thereon.
18. A method comprising:
focusing, via a head mounted augmented reality display device, virtual images at a plurality of depth planes among a real world view, the focusing including:
guiding, via a waveguide assembly, light in a lateral direction parallel to an output surface of the waveguide assembly,
outcoupling, via the waveguide assembly, the guided light through the output surface; and
receiving, via an adaptive lens assembly disposed on a first side of the waveguide assembly, outcoupled light from the waveguide assembly, and
selectively switching the adaptive lens assembly between a plurality of states having different optical powers to focus the virtual images at the plurality of plane depths among the real world view while simultaneously refocusing the real world view to appear without substantial distortion,
wherein a polarizing reflector is interposed between the adaptive lens assembly and the waveguide assembly, wherein the polarizing reflector comprises cholesteric liquid crystals configured such that the polarizing reflector is configured to pass therethrough circular polarized light having a first polarization and to reflect circular polarized light having a second polarization.
19. The method of claim 18 , further comprising on a second side of the waveguide assembly a nonpolarizing reflector, wherein the nonpolarizing reflector is configured to reflect and to alter the polarization of circular polarized light incident thereon having the second circular polarization.