Optical assembly with holographic optics for folded optical path
An optical device for a head-mounted display device includes a first partial reflector and a second partial reflector positioned relative to the first partial reflector so that the second partial reflector receives first light transmitted through the first partial reflector and reflects at least a portion of the first light toward the first partial reflector as second light. At least a portion of the second light is reflected by the first partial reflector as third light, and at least a portion of the third light is transmitted through the second partial reflector. At least one of the first partial reflector or the second partial reflector includes a reflective holographic element.
1. An optical device for a head-mounted display device, the optical device comprising:
a first partial reflector;
a second partial reflector positioned relative to the first partial reflector so that the second partial reflector receives first light transmitted through the first partial reflector and reflects at least a portion of the first light toward the first partial reflector as second light, wherein:
at least a portion of the second light is reflected by the first partial reflector as third light, and at least a portion of the third light is transmitted through the second partial reflector, and
at least one of the first partial reflector or the second partial reflector comprises a reflective holographic element, and
a third partial reflector.
2. The optical device of claim 1 , wherein the reflective holographic element has a freeform phase profile.
3. The optical device of claim 1 , wherein the reflective holographic element is a wavelength sensitive element having different phase profiles for each of red, green, and blue wavelengths.
4. The optical device of claim 3 , wherein the phase profiles are encoded in the reflective holographic element by wavelength multiplexing.
5. The optical device of claim 3 , wherein the reflective holographic element includes a stack of two or more holograms, each of which is sensitive to a distinct wavelength range.
6. The optical device of claim 1 , wherein the reflective holographic element includes a pitch-gradient polarization volume hologram.
7. The optical device of claim 6 , wherein the pitch-gradient polarization volume hologram includes cholesteric liquid crystals.
8. The optical device of claim 1 , wherein the third partial reflector is a reflective holographic element.
9. The optical device of claim 1 , wherein the first partial reflector comprises a volume Bragg grating and the second partial reflector comprises a reflective polarizer.
10. The optical device of claim 1 , wherein the reflective holographic element is selected from the group consisting of volume Bragg grating, polarization volume hologram and Pancharatnam Berry Phase element.
11. The optical device of claim 1 , wherein the second partial reflector is spaced apart by an air gap from the first partial reflector, and a size of the air gap is configured to be varied.
12. An optical device for a head-mounted display device, the optical device comprising:
a first partial reflector; and
a second partial reflector positioned relative to the first partial reflector so that the second partial reflector receives first light transmitted through the first partial reflector and reflects at least a portion of the first light toward the first partial reflector as second light, wherein:
at least a portion of the second light is reflected by the first partial reflector as third light, and at least a portion of the third light is transmitted through the second partial reflector,
at least one of the first partial reflector or the second partial reflector comprises a reflective holographic element, and
the first partial reflector comprises a volume Bragg grating and the second partial reflector comprises a polarization volume hologram.
13. The optical device of claim 12 , wherein the reflective holographic element has a freeform phase profile.
14. The optical device of claim 12 , wherein the reflective holographic element is a wavelength sensitive element having different phase profiles for each of red, green, and blue wavelengths.
15. An optical device for a head-mounted display device, the optical device comprising:
a first partial reflector; and
a second partial reflector positioned relative to the first partial reflector so that the second partial reflector receives first light transmitted through the first partial reflector and reflects at least a portion of the first light toward the first partial reflector as second light, wherein:
at least a portion of the second light is reflected by the first partial reflector as third light, and at least a portion of the third light is transmitted through the second partial reflector,
at least one of the first partial reflector or the second partial reflector comprises a reflective holographic element, and
the first partial reflector comprises a polarization volume hologram and the second partial reflector comprises a reflective polarizer.
16. The optical device of claim 15 , wherein the reflective holographic element has a freeform phase profile.
17. The optical device of claim 15 , wherein the reflective holographic element is a wavelength sensitive element having different phase profiles for each of red, green, and blue wavelengths.
18. An optical device for a head-mounted display device, the optical device comprising:
a first partial reflector; and
a second partial reflector positioned relative to the first partial reflector so that the second partial reflector receives first light transmitted through the first partial reflector and reflects at least a portion of the first light toward the first partial reflector as second light, wherein:
at least a portion of the second light is reflected by the first partial reflector as third light, and at least a portion of the third light is transmitted through the second partial reflector,
at least one of the first partial reflector or the second partial reflector comprises a reflective holographic element, and
the first partial reflector has optical power and the second partial reflector is positioned away from a focal plane of the first partial reflector.
19. The optical device of claim 18 , wherein the second partial reflector has no optical power.
20. The optical device of claim 18 , wherein the reflective holographic element has a freeform phase profile.