Pancake lens including diffuser
Various embodiments set forth a foveated display system and components thereof. The foveated display system includes a peripheral display module disposed in series with a foveal display module. The peripheral display module is configured to generate low-resolution, large field of view imagery for a user's peripheral vision. The foveal display module is configured to perform foveated rendering in which high-resolution imagery is focused towards a foveal region of the user's eye gaze. The peripheral display module may include a diffuser that is disposed within a pancake lens, which is a relatively compact design. The foveal display module may include a Pancharatnam-Berry Phase grating stack that increases the steering range of a beam-steering device such that a virtual image can be steered to cover an entire field of view visible to the user's eye.
1. A pancake lens, comprising:
a half-wave plate;
a polarization- and angular-selective mirror;
a diffuser; and
a half mirror.
2. The pancake lens of claim 1 , wherein the diffuser is polarization and angular selective.
3. The pancake lens of claim 2 , wherein the diffuser is configured to reflect and diffuse light having one handedness of polarization that is incident on the diffuser at an angle.
4. The pancake lens of claim 3 , wherein:
the light incident on the diffuser at the angle includes light emitted by a light source that is projected onto the diffuser via the polarization- and angular-selective mirror and the half-wave plate;
the polarization- and angular-selective mirror is configured to maintain a handedness of polarization of the light emitted by the light source; and
the half-wave plate is configured to change a handedness of polarization of light that has passed through the polarization- and angular-selective mirror.
5. The pancake lens of claim 3 , wherein:
the diffused light is further passed through the half-wave plate, which changes a handedness of polarization of the diffused light;
light that has passed through the half-wave plate is reflected by the polarization- and angular-selective mirror;
light that has been reflected by the polarization- and angular-selective mirror is passed for a second time through the half-wave plate, which changes a handedness of polarization of the light that has been reflected by the polarization- and angular-selective mirror;
light that has passed for the second time through the half-wave plate is passed through the diffuser;
light that has passed through the diffuser is reflected by the half mirror, which changes a handedness of polarization of the light that has passed through the diffuser;
light that has been reflected by the half mirror is passed for a second time through the diffuser;
light that has passed for the second time through the diffuser is passed for a third time through the half-wave plate, which changes a handedness of polarization of the light that has passed for the second time through the diffuser; and
light that has passed for the third time through the half-wave plate is passed through the polarization- and angular-selective mirror toward an eye box.
6. The pancake lens of claim 2 , wherein the diffuser is further wavelength selective.
7. The pancake lens of claim 1 , wherein the diffuser comprises a cholesteric liquid crystal material.
8. The pancake lens of claim 1 , wherein the half mirror has focal power.
9. The pancake lens of claim 1 , wherein the pancake lens is included in a peripheral display system configured to generate a low-resolution, high field of view background image.
10. The pancake lens of claim 1 , wherein the pancake lens is included in a head-mounted display.
11. A display system, comprising:
a projector; and
a pancake lens comprising a diffuser and two mirrors, wherein the diffuser is disposed between the two mirrors.
12. The display system of claim 11 , wherein the projector is configured to project light onto the diffuser.
13. The display system of claim 11 , wherein the two mirrors comprise a polarization- and angular-selective mirror and a half mirror, and the pancake lens further comprises a half-wave plate.
14. The display system of claim 11 , wherein the diffuser is polarization and angular selective.
15. The display system of claim 14 , wherein the diffuser is configured to reflect and diffuse light having one handedness of polarization that is incident on the diffuser within a range of angles.
16. The display system of claim 11 , wherein light bounces twice within the pancake lens.
17. The display system of claim 11 , further comprising a condenser.
18. The display system of claim 11 , wherein the display system is included in an artificial reality system.
19. A method, comprising:
determining an image to display; and
projecting the image onto a pancake lens comprising a diffuser and two mirrors, wherein the diffuser is disposed between the two mirrors.
20. The method of claim 19 , wherein the diffuser is polarization and angular selective.