Varifocal optical assembly providing astigmatism compensation

1. A varifocal optical assembly comprising:

an astigmatism compensation optical assembly comprising:

a first astigmatism compensation optical module comprising a first plurality of optical elements comprising Pancharatnam-Berry phase (PBP) lenses, PBP gratings, polarization sensitive hologram (PSH) lenses, PSH gratings, metamaterials, or combinations thereof, wherein the first plurality of optical elements are configured to compensate for astigmatism in a first axis and comprise a property associated with Zernike polynomial Z 2 −2 ; and

a second astigmatism compensation optical module comprising a second plurality of optical elements comprising PBP lenses, PBP gratings, PSH lenses, PSH gratings, metamaterials, or combinations thereof, wherein the second plurality of optical elements are configured to compensate for astigmatism in a second axis and comprise a property associated with Zernike polynomial Z 2 2 , wherein each of the first astigmatism compensation optical module and the second astigmatism compensation module are configurable between a plurality of optical powers to provide a plurality of cylindrical and axial correction values.

2. The varifocal optical assembly of claim 1 , further comprising a spherically lensing optical module.

3. The varifocal optical assembly of claim 2 , wherein the spherically lensing optical module comprises at least one of:

a liquid lens;

a plurality of movable lenses; or

a third plurality of optical elements comprising PBP lenses, PBP gratings, PSH lenses, PSH gratings, metamaterials, or combinations thereof.

4. The varifocal optical assembly of claim 1 , wherein the first and second plurality of optical elements comprise PBP lenses, PBP gratings, PSH lenses, PSH gratings, or a combination thereof, and wherein the property comprises a liquid crystal director pattern.

5. The varifocal optical assembly of claim 1 , wherein each optical element of the first and second plurality of optical elements comprises a PBP lens.

6. The varifocal optical assembly of claim 1 , wherein the first astigmatism compensation optical module and the second astigmatism compensation optical module each comprise at least three optical stages, each optical stage comprising at least one optical element, and wherein at least some of the optical elements have different optical powers.

7. The varifocal optical assembly of claim 6 , wherein one or more optical stages in each of the first astigmatism compensation optical module and the second astigmatism compensation optical module comprises a switchable retarder and an optical element comprising a PBP lens, a PBP grating, a PSH lens, or a PSH grating, wherein:

the switchable retarder is configurable to be in an “off” state or an “on” state, wherein

in the “off” state, the switchable optical retarder is configured to convert light of a first or a second polarization into light of the second polarization or light of the first polarization, respectively; and

in the “on” state, the switchable optical retarder transmits incident light without changing its polarization;

the optical element comprising the PBP lens, the PBP grating, the PSH lens, or the PSH grating is configured to receive light transmitted through the switchable retarder and has an optical power that is dependent on whether the light transmitted through the optical element of the first type has the first polarization or the second polarization.

8. The varifocal optical assembly of claim 1 , wherein the optical power of the first astigmatism compensation optical module and the optical power of the second astigmatism compensation optical module are configured based on astigmatism of a user of the varifocal optical assembly.

9. The varifocal optical assembly of claim 1 , further comprising at least one additional optical element, wherein the optical power of the first astigmatism compensation optical module and the optical power of the second astigmatism compensation optical module are configured to compensate for optical aberrations introduced by the at least one additional optical element.

10. The varifocal optical assembly of claim 1 , wherein each optical element has an optical power that is a power of about 2.

11. The varifocal optical assembly of claim 1 , wherein a combination of the first and second astigmatism compensation optical modules is configurable to exhibit a plurality of cylindrical optical powers of between −2 Diopters and +2 Diopters and a plurality of corrective axes between 0 and 180 degrees.

12. A head mounted display comprising:

a display configured to emit image light; and

a varifocal optical assembly configured to provide astigmatism compensation, the varifocal optical assembly comprising:

an astigmatism compensation optical assembly comprising:

a first astigmatism compensation optical module comprising a first plurality of optical elements comprising PBP lenses, PBP gratings, PSH lenses, PSH gratings, metamaterials or combinations thereof, wherein the first plurality of optical elements are configured to compensate for astigmatism in a first axis and comprise a property associated with Zernike polynomial Z 2 −2 ; and

a second astigmatism compensation optical module comprising a second plurality of optical elements comprising PBP lenses, PBP gratings, PSH lenses, PSH gratings, metamaterials, or combinations thereof, wherein the second plurality of optical elements are configured to compensate for astigmatism in a second axis and comprise a property associated with Zernike polynomial Z 2 2 , wherein each of the first astigmatism compensation optical module and the second astigmatism compensation module are configurable between a plurality of optical powers to provide a plurality of cylindrical and axial correction values.

13. The head mounted display of claim 12 , wherein the varifocal optical assembly further comprises a spherically lensing optical module.

14. The head mounted display of claim 12 , wherein the first and second plurality of optical elements comprise PBP lenses, PBP gratings, PSH lenses, PSH gratings, or a combination thereof, and wherein the property comprises a liquid crystal director pattern.

15. The head mounted display of claim 12 , wherein the first astigmatism compensation optical module and the second astigmatism compensation optical module each comprise at least three optical stages, each optical stage comprising at least one optical element, and wherein at least some of the optical elements have different optical powers.

16. The head mounted display of claim 12 , wherein the optical power of the first astigmatism compensation optical module and the optical power of the second astigmatism compensation optical module are configured based on astigmatism of a user of the head mounted display.

17. A method comprising:

transmitting light through a first astigmatism compensation optical module comprising a first plurality of optical stages, each optical stage comprising an optical element from a second plurality of optical elements comprising Pancharatnam-Berry-phase (PBP) lenses, PBP gratings, polarization sensitive hologram (PSH) lenses, PSH gratings, metamaterials, or combinations thereof, wherein the first plurality of optical elements are configured to compensate for astigmatism in a first axis and comprise a property associated with Zernike polynomial Z 2 −2 , wherein each stage of the first plurality of optical stages is configurable to be in any of a plurality of states including a first state and a second state;

adjusting a first focal power of the first astigmatism compensation optical module by changing respective states of one or more optical stages of the first plurality of optical stages;

transmitting light through a second astigmatism compensation optical module comprising a second plurality of optical stages, each optical stage comprising an optical element from a second plurality of optical elements comprising PBP lenses, PBP gratings, PSH lenses, PSH gratings, metamaterials, or combinations thereof, wherein the second plurality of optical elements are configured to compensate for astigmatism in a first axis comprise a property associated with Zernike polynomial Z 2 2 , wherein each stage of the second plurality of optical stages is configurable to be in any of a plurality of states including a first state and a second state; and

adjusting a second focal power of the second astigmatism compensation optical module by changing respective states of one or more optical stages of the second plurality of optical stages.

18. The method of claim 17 , further comprising:

transmitting light through a spherically lensing optical module comprising a third plurality of optical stages, each optical stage comprising an optical element from a third plurality of optical elements comprising PBP lenses, PBP gratings, PSH lenses, PSH gratings, or combinations thereof, wherein the first plurality of optical elements comprise a liquid crystal director pattern associated with Zernike polynomial Z 2 0 , wherein each stage of the first plurality of optical stages is configurable to be in any of a plurality of states including a first state and a second state; and

adjusting a spherical focal power of the spherically lensing optical module by changing respective states of one or more optical stages of the first plurality of optical stages.

19. The method of claim 17 , wherein the first astigmatism compensation optical module is configured to correct vertical astigmatism in a first plane normal to a principal axis of the varifocal optical assembly.

20. The method of claim 19 , wherein the second astigmatism compensation optical module is configured to correct oblique astigmatism.