Varifocal structure comprising a liquid lens structure in optical series with a liquid crystal lens in a head-mounted display
A varifocal block includes liquid crystal (LC) lens and a liquid lens structure in optical series. The LC lens has a plurality of optical states, including an additive state that adds optical power to the LC lens and a subtractive state that removes optical power from the LC lens. The liquid lens structure comprises a transparent substrate layer, a deformable membrane, and a volume of liquid enclosed between the transparent substrate layer and the deformable membrane. The deformable membrane has an adjustable range of optical power dependent on an adjustable curvature of the deformable membrane. The plurality of optical states of the LC lens and the adjustable range of optical power of the liquid lens structure together provide a continuous range of optical power for the varifocal block.
1. A varifocal block comprising:
a liquid crystal (LC) lens that has a plurality of optical states, the plurality of optical states including an additive state that adds optical power to the LC lens and a subtractive state that removes optical power from the LC lens; and
a liquid lens structure in optical series with the LC lens, comprising:
a transparent substrate layer,
a deformable membrane, wherein the deformable membrane has an adjustable range of optical power that is based in part on adjusting a curvature of the deformable membrane, and
a volume of liquid enclosed between the transparent substrate layer and the deformable membrane; and
wherein the plurality of optical states of the LC lens and the adjustable range of optical power of the liquid lens structure together provide a continuous range of adjustment of optical power for the varifocal block.
2. The varifocal block of claim 1 , further comprising a switchable half waveplate, and the LC lens is positioned between the liquid lens structure and the switchable half waveplate.
3. The varifocal block of claim 2 , wherein, based in part on a state of the switchable half waveplate and a state of the LC lens, the continuous range of adjustment of optical power for the varifocal block is selected from the group consisting of:
d to (D+d), −d to (−d+D), and 0 to D,
where:
−d is the optical power of the LC lens in the subtractive state,
D is a maximum optical power of the adjustable range of the liquid lens structure, and
d is the optical power of the LC lens in the additive state.
4. The varifocal block of claim 1 , further comprising a circular polarizer, and the LC lens is positioned between the liquid lens structure and the circular polarizer.
5. The varifocal block of claim 4 , wherein, based in part on a state of the LC lens, the continuous range of adjustment of optical power for the varifocal block is selected from the group consisting of:
−d to (D−d), d to (d+D), and (d−D) to d,
where:
−d is the optical power of the LC lens in the subtractive state,
D is a maximum optical power of the adjustable range of the liquid lens structure, and
d is the optical power of the LC lens in the additive state.
6. The varifocal block of claim 1 , further comprising a circular polarizer that is positioned between the liquid lens structure and the LC lens.
7. The varifocal block of claim 6 , wherein, based in part on a state of the LC lens, the continuous range of adjustment of optical power for the varifocal block is selected from the group consisting of:
−d to (D−d), d to (d+D)
where:
−d is the optical power of the LC lens in the subtractive state,
D is a maximum optical power of the adjustable range of the liquid lens structure, and
d is the optical power of the LC lens in the additive state.
8. The varifocal block of claim 1 , wherein the LC lens is a Pancharatnam Berry Phase (PBP) liquid crystal lens.
9. The varifocal block of claim 1 , wherein a color dispersion caused by the liquid lens structure is opposite of a color dispersion caused by the LC lens.
10. The varifocal block of claim 1 , wherein the volume of liquid enclosed between the transparent substrate layer and the deformable membrane is constant.
11. A head-mounted display (HMD) comprising:
a varifocal block that receives content from an electronic display, and presents the content over a plurality of image planes that are associated with different optical powers of the varifocal block, the varifocal block comprising:
a liquid crystal (LC) lens that has a plurality of optical states, the plurality of optical states including an additive state that adds optical power to the LC lens and a subtractive state that removes optical power from the LC lens, and
a liquid lens structure in optical series with the LC lens, comprising:
a transparent substrate layer,
a deformable membrane, wherein the deformable membrane has an adjustable range of optical power that is based in part on adjusting a curvature of the deformable membrane, and
a volume of liquid enclosed between the transparent substrate layer and the deformable membrane, and
wherein the plurality of optical states of the LC lens and the adjustable range of optical power of the liquid lens structure together provide a continuous range of adjustment of optical power for the varifocal block, and each value of optical power over the continuous range of adjustment of optical power corresponds to a different image plane of the plurality of image planes.
12. The HMD of claim 11 , further comprising a switchable half waveplate, and the LC lens is positioned between the liquid lens structure and the switchable half waveplate.
13. The HMD of claim 12 , wherein, based in part on a state of the switchable half waveplate and a state of the LC lens, the continuous range of adjustment of optical power for the varifocal block is selected from the group consisting of:
d to (D+d), −d to (−d+D), and 0 to D,
where:
−d is the optical power of the LC lens in the subtractive state,
D is a maximum optical power of the adjustable range of the liquid lens structure, and
d is the optical power of the LC lens in the additive state.
14. The HMD of claim 11 , further comprising a circular polarizer, and the LC lens is positioned between the liquid lens structure and the circular polarizer.
15. The HMD of claim 14 , wherein, based in part on a state of the LC lens, the continuous range of adjustment of optical power for the varifocal block is selected from the group consisting of:
−d to (D−d), d to (d+D), and (d−D) to d,
where:
−d is the optical power of the LC lens in the subtractive state,
D is a maximum optical power of the adjustable range of the liquid lens structure, and
d is the optical power of the LC lens in the additive state.
16. The HMD of claim 11 , further comprising a circular polarizer that is positioned between the liquid lens structure and the LC lens.
17. The HMD of claim 16 , wherein, based in part on a state of the LC lens, the continuous range of adjustment of optical power for the varifocal block is selected from the group consisting of:
−d to (D−d), d to (d+D)
where:
−d is the optical power of the LC lens in the subtractive state,
D is a maximum optical power of the adjustable range of the liquid lens structure, and
d is the optical power of the LC lens in the additive state.
18. The HMD of claim 11 , wherein the LC lens is a Pancharatnam Berry Phase (PBP) liquid crystal lens.
19. The HMD of claim 11 , wherein a color dispersion caused by the liquid lens structure is opposite of a color dispersion caused by the LC lens.
20. The varifocal block of claim 11 , wherein the volume of liquid enclosed between the transparent substrate layer and the deformable membrane is constant.