Compact polarization-based multi-pass optical architectures
Optical systems that can produce digitally switchable optical power, optical pathlength, or both. It can apply to reconfigurable wide-angle optical systems that are compact, light-weight, and light-efficient. Architectures that increase pathlength can utilize polarization splitters to produce an additional round-trip of one or more optical cavities. Changing the focus distance of synthetic imagery in augmented/virtual reality systems is an example of an application where the techniques taught herein are particularly well suited. Passive double-cavity systems can be used to increase the throughput and decrease the stray-light/ghosts in polarization-based compact wide-angle lenses.
1. A double-cavity optical system with increased light-efficiency, comprising:
a first reflective-polarizer;
a single shared central partial-reflector; and
a second reflective-polarizer;
wherein the first cavity is formed between the first reflective-polarizer and the single shared central partial reflector and the second cavity is formed between the single shared central partial-reflector and the second reflective polarizer, the first and second cavities being distinct cavities separated by the single shared central partial-reflector;
wherein a first light path comprises:
an initial reflection by the shared central partial-reflector; and
a subsequent transmission by the shared central partial-reflector;
wherein a second light path comprises an initial transmission by the shared central partial reflector;
wherein the first light path and the second light path are superimposed after the subsequent transmission of the first light path; and
wherein the geometries of the first reflective-polarizer and the second-reflective polarizer are the same.
2. The optical system of claim 1 , wherein the first and second reflective-polarizers are one of a wire-grid, a multi-layer stretched-film, or a cholesteric liquid crystal.
3. The optical system of claim 2 , further comprising a quarter-wave retarder in each of the first and second optical cavities.
4. The optical system of claim 1 , wherein:
a first image is produced by the first optical cavity;
a second image with a same content as the first image is produced by the second optical cavity; and
the first image and the second image are superimposed at a viewer to create a superimposed image with the same content as the first and second images and with a greater intensity.
5. The optical system of claim 1 , wherein the geometries of the first and second reflective-polarizers are one of concave, convex, or flat.
6. The optical system of claim 1 , wherein each of cavity 1 and cavity 2 forms a wide-angle collimator.
7. The optical system of claim 1 , further including an input electronic display device.
8. The optical system of claim 7 , wherein the polarization of display light is selected to maximize the transmission of the first reflective-polarizer.
9. The optical system of claim 8 , further including a polarizer after the second reflective-polarizer that maximizes the transmission of light that completes three-passes of cavity 1 and cavity 2 .
10. The optical system of claim 8 , wherein the display transmits linear polarization that is maximally transmitted by the first wire-grid or stretched-polymer reflective-polarizer.
11. The optical system of claim 8 , wherein the display transmits circular polarization that is maximally transmitted by the first cholesteric liquid crystal reflective-polarizer.
12. A high-efficiency imaging system, comprising:
an electronic display;
a first optical cavity formed by a first reflective-polarizer and a single shared partial-reflector; and
a second optical cavity formed by the single shared partial-reflector and a second reflective-polarizer, the first and second optical cavities being distinct cavities separated by the single shared partial-reflector;
wherein the geometries of the first reflective-polarizer and the second reflective-polarizer are the same;
wherein display light is transmitted by the first reflective-polarizer and split into optical Path 1 and Path 2 by the single shared partial-reflector, such that Path 1 display light is transmitted when Path 2 display light is reflected;
wherein Path 1 display light is transmitted by the single shared partial-reflector, reflected by the second reflective-polarizer, reflected by the single shared partial-reflector and transmitted by the second reflective-polarizer;
wherein Path 2 light is reflected by the single shared partial-reflector, reflected by the first reflective-polarizer, transmitted by the single shared partial-reflector and transmitted by the second reflective-polarizer; and
wherein Path 1 and Path 2 display light are superimposed at the output of the imaging system, increasing the signal of Path 1 alone and of Path 2 display light alone.
13. The optical system of claim 12 , wherein the first reflective-polarizer is a concave reflector for Path 2 display light and the second reflective-polarizer is a concave reflector for Path 1 display light.
14. The optical system of claim 12 , wherein the first and second reflective-polarizers are one of a wire-grid, a multi-layer stretched-film, or a cholesteric liquid crystal.
15. The optical system of claim 12 , further comprising a quarter-wave retarder in each of the first and second optical cavities.
16. The optical system of claim 12 , wherein images produced by the first and second optical cavities are superimposed at a viewer.
17. The optical system of claim 12 , wherein the polarization of display light is selected to maximize the transmission of the first reflective-polarizer.
18. The optical system of claim 12 , further comprising a polarizer after the second reflective-polarizer that maximizes the transmission of Path 1 and Path 2 light.
19. The optical system of claim 12 , wherein the display transmits linear polarization that is maximally transmitted by t-Re-first wire-grid or stretched-polymer reflective-polarizer.
20. The optical system of claim 12 , wherein the display transmits circular polarization that is maximally transmitted by a first cholesteric liquid crystal reflective-polarizer.
21. A high-efficiency optical system, comprising:
an electronic display;
a first linear polarizer with absorption-axis parallel to the reflection-axis of a first linear reflective-polarizer;
a first optical cavity formed by the first linear reflective-polarizer, a first quarter-wave retarder, and a single shared central partial-reflector; and
a second optical cavity formed by the shared partial-reflector, a second quarter-wave retarder, and a second linear reflective-polarizer;
the first and second cavities being distinct cavities separated by the single shared partial-reflector;
wherein a first light path comprises:
an initial reflection by the shared central partial-reflector; and
a subsequent transmission by the shared central partial-reflector;
wherein a second light path comprises an initial transmission by the shared central partial-reflector;
wherein the first light path and the second light path are superimposed after the subsequent transmission of the first light path; and
wherein the first quarter-wave retarder and the second quarter-wave retarder convert between linear and circular polarization.
22. The optical system of claim 21 , further including a second linear polarizer following the second reflective-polarizer with absorption-axis parallel to the reflection-axis of the second reflective-polarizer.
23. The optical system of claim 21 , wherein the first and second reflective-polarizers are concave reflectors.
24. The optical system of claim 21 , wherein the first and second reflective-polarizers are one of a wire-grid and a multi-layer stretched-film.
25. The optical system of claim 21 , wherein images produced by the first and second optical cavities are superimposed at a viewer.