Method of selecting a state of a switchable half waveplate and selecting an optical power of a liquid lens structure in optical series with a liquid crystal lens in a head-mounted display

1. A method comprising:

selecting a state of a switchable half waveplate (SHWP) of a varifocal block;

selecting an optical power of a liquid lens structure of the varifocal block from a range of optical power, the liquid lens structure in optical series with a liquid crystal (LC) lens and the SHWP; and

adjusting the SHWP to the selected state and the liquid lens structure to the selected optical power,

wherein a range of adjustment of optical power for the varifocal block is based in part on the state of the SHWP and the range of optical power of the liquid lens structure.

2. The method of claim 1 , wherein the range of optical power of the liquid lens structure is a continuous range of optical power.

3. The method of claim 1 , wherein the range of adjustment of optical power for the varifocal block is a continuous range of adjustment of optical power.

4. The method of claim 1 , wherein the LC lens is positioned between the liquid lens structure and the SHWP.

5. The method of claim 4 , wherein, based in part on a state of the SHWP and a state of the LC lens, the 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 range of the liquid lens structure, and

d is the optical power of the LC lens in the additive state.

6. The method of claim 1 , wherein the LC lens is positioned between the liquid lens structure and a circular polarizer.

7. The method of claim 1 , wherein a circular polarizer is positioned between the liquid lens structure and the LC lens.

8. The method of claim 1 , wherein the LC lens is a Pancharatnam Berry Phase (PBP) liquid crystal lens.

9. The method 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 method of claim 1 , further comprising:

presenting content from an electronic display of a head-mounted display at an image plane associated with the optical power of the varifocal block.

11. The method of claim 1 , wherein selecting the optical power of the liquid lens structure from the range of optical powers, comprises:

selecting a curvature for a deformable membrane of the liquid lens.

12. The method of claim 1 , further comprising:

determining a gaze line for each of the user based on a tracked eye position for each eye;

determining a vergence depth based on an estimated intersection of the gaze lines; and

wherein the selected state of the SHWP and the selected optical power of the liquid lens structure are based in part on the vergence depth.

13. 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,

a liquid lens structure in optical series with the LC lens, the liquid lens structure having a range of optical power, and

a switchable half waveplate (SHWP) that is in optical series with the liquid lens structure and the LC lens,

wherein the HMD is configured to:

select a state of the SHWP,

select an optical power of the liquid lens structure from the range of optical power; and

adjust the SHWP to the selected state and the liquid lens structure to the selected optical power, and

wherein a range of adjustment of optical power for the varifocal block is based in part on the state of the SHWP and the range of optical power of the liquid lens structure.

14. The HMD of claim 13 , wherein the range of optical power of the liquid lens structure is a continuous range of optical power.

15. The HMD of claim 13 , wherein the range of adjustment of optical power for the varifocal block is a continuous range of adjustment of optical power.

16. The HMD of claim 13 , further comprising one of:

a first circular polarizer, and the LC lens is positioned between the liquid lens structure and the first circular polarizer; and

a second circular polarizer that is positioned between the liquid lens structure and the LC lens.

17. The HMD of claim 13 , wherein the LC lens is positioned between the liquid lens structure and the SHWP.

18. The HMD of claim 13 , wherein the LC lens is a Pancharatnam Berry Phase (PBP) liquid crystal lens.

19. The HMD of claim 13 , wherein a color dispersion caused by the liquid lens structure is opposite of a color dispersion caused by the LC lens.

20. A non-transitory computer readable medium configured to store program code instructions, when executed by a processor, cause the processor to perform steps comprising:

selecting a state of a switchable half waveplate (SHWP) of a varifocal block;

selecting an optical power of a liquid lens structure of the varifocal block from a range of optical power, the liquid lens structure in optical series with a liquid crystal (LC) lens and the SHWP; and

adjusting the SHWP to the selected state and the liquid lens structure to the selected optical power,

wherein a range of adjustment of optical power for the varifocal block is based in part on the state of the SHWP and the range of optical power of the liquid lens structure.