Freeform polarization volume hologram

1. A polarization volume hologram (PVH) lens comprising:

a PVH layer configured to reflect an incident light via Bragg diffraction, including a first region and a second region encircling the first region,

wherein the first region is configured to reflect the incident light when the incident light has a first handedness, and transmit the incident light therethrough when the incident light has a second handedness orthogonal to the first handedness, and

wherein the second region is configured to reflect the incident light when the incident light has the second handedness, and transmit the incident light therethrough when the incident light has the first handedness.

2. The PVH lens of claim 1 , wherein the first region and the second region have different optical powers.

3. The PVH lens of claim 1 , wherein a first optical axis of the first region and a second optical axis of the second region extend in different directions and form non-zero angles with respect to a surface of the PVH lens.

4. The PVH lens of claim 1 , wherein a second field of view (FOV) of the second region encompasses a first FOV of the first region.

5. The PVH lens of claim 4 , wherein a second image formed by the second region has a lower resolution than a first image formed by the first region.

6. The PVH lens of claim 1 , wherein the first region and the second region are configured to respond to incident lights of different wavelengths.

7. The PVH lens of claim 6 , wherein the first region is configured to respond to the incident light when the incident light has a wavelength of about 850 nm, and the second region is configured to respond to the incident light when the incident light has a wavelength of about 940 nm.

8. The PVH lens of claim 1 , wherein the first region is configured to reflect a left-handed circularly polarized light and the second region is configured to reflect a right-handed circularly polarized light.

9. The PVH lens of claim 1 , further comprising:

a transition region between the first region and the second region, the transition region having an optical power that varies gradually from the first region to the second region.

10. An optical system comprising:

a polarization volume hologram (PVH) lens including:

a PVH layer configured to reflect an incident light via Bragg diffraction, the PVH layer including a first region and a second region encircling the first region,

wherein the first region is configured to reflect the incident light when the incident light has a first handedness, and transmit the incident light therethrough when the incident light has a second handedness orthogonal to the first handedness, and

wherein the second region is configured to reflect the incident light when the incident light has the second handedness, and transmit the incident light therethrough when the incident light has the first handedness; and

an optical sensor configured to generate an image based on the incident light reflected by the PVH layer.

11. The optical system of claim 10 , wherein:

the PVH layer is a first PVH layer; and

the PVH lens further includes a second PVH layer coupled to the first PVH layer,

wherein the second PVH layer includes a third region and a fourth region encircling the third region,

wherein the third region is configured to reflect the incident light when the incident light has the first handedness, and transmit the incident light therethrough when the incident light has the second handedness, and

wherein the fourth region is configured to reflect the incident light when the incident light has the second handedness, and transmit the incident light therethrough when the incident light has the first handedness.

12. The optical system of claim 10 , further comprising:

a substrate, the PVH layer being formed over the substrate; and

a temple arm connected to the substrate;

wherein the optical sensor is mounted on the temple arm and faces the PVH lens.

13. The optical system of claim 10 , wherein the PVH layer is configured to reflect an infrared (IR) light reflected from an eye.

14. The optical system of claim 13 , further comprising:

a light source configured to emit a light beam having a wavelength in IR spectrum.

15. The optical system of claim 10 , wherein:

the PVH layer is a first PVH layer, and

the PVH lens further includes a second PVH layer coupled to the first PVH layer,

wherein the second PVH layer includes a third region and a fourth region encircling the third region,

wherein the third region is configured to reflect the incident light when the incident light has the second handedness, and transmit the incident light therethrough when the incident light has the first handedness, and

wherein the fourth region is configured to reflect the incident light when the incident light has the first handedness, and transmit the incident light therethrough when the incident light has the second handedness.