Etendue-preserving light coupling system having light output aperture smaller than light input aperture
This disclosure provides systems, methods and apparatus for providing illumination. In one aspect, an etendue preserving optical coupling system configured to: receive incident light through an input aperture; and emit the incident light through an output aperture having an area smaller than an area of the input aperture is provided. The light output from the optical coupling system is coupled into a light receiving system including material having substantially the same refractive index as the refractive index of the material of the optical coupling system. The light receiving system includes a light guide configured to internally propagate the redirected light and to release light to illuminate the ambient environment.
1. An optical system comprising:
an optical coupling system including:
a light input surface configured to receive incident light through an input aperture; and
a light output surface configured to emit the incident light through an output aperture having an area smaller than an area of the input aperture,
wherein the optical coupling system is configured to couple to an optical source separated from the light input surface by a gap, the gap including a medium having lower refractive index than the refractive index of material forming the optical coupling system; and
an optical receiving system optically coupled to the light output surface of the optical coupling system, the optical receiving system including:
a light redirecting element configured to receive light from the light output surface of the optical coupling system along an incident direction and redirect the light along an output direction that is at an angle with respect to the incident direction; and
a light guide configured to internally propagate the redirected light,
wherein a material of the optical receiving system optically coupling with the output aperture has substantially the same refractive index as material of the optical coupling system, and
wherein the optical coupling system is configured to preserve etendue of the light emitted from the output surface relative to the etendue of light incident on the input surface of the optical coupling system.
2. The optical system of claim 1 , wherein a ratio of the area of the input aperture to the area of the output aperture is approximately n 2 , where n is the refractive index of the material forming the optical coupling system.
3. The optical system of claim 1 , wherein the light input surface is square, rectangular, circular or polygonal.
4. The optical system of claim 1 , wherein the gap is filled with air.
5. The optical system of claim 1 , wherein the light redirecting element includes an etendue preserving reflector.
6. The optical system of claim 1 , wherein the light redirecting element includes a reflecting surface.
7. The optical system of claim 6 , wherein the reflecting surface has a polynomially shaped cross-section.
8. The optical system of claim 6 , wherein the reflecting surface is configured to redirect a first portion of light incident thereon and transmit a portion of light incident thereon.
9. The optical system of claim 6 , wherein the reflecting surface includes a plurality of optical apertures configured to transmit light.
10. The optical system of claim 1 , wherein the light redirecting element includes an input aperture of the light guide.
11. The optical system of claim 1 , wherein the light redirecting element includes a cylindrical light output surface configured to couple light into a cylindrical input surface of the light guide.
12. The optical system of claim 1 , wherein the light redirecting element includes a rectangular light output surface configured to couple light into a rectangular input surface of the light guide.
13. The optical system of claim 1 , wherein the angle between the output direction and the incident direction is less than or equal to 160 degrees.
14. The optical system of claim 1 , wherein the light guide has a light output surface, wherein a cross-section of the light guide in a plane perpendicular to the light output surface is tapered such that a surface opposite the light output surface is inclined and disposed at an angle α 1 with respect to the light guide output surface, the angle α 1 being less than 15 degrees.
15. The optical system of claim 14 , wherein the light guide has a shape of a tapered disc, wherein the light redirecting element is disposed in the interior of the tapered disc.
16. The optical system of claim 15 , wherein the output aperture of the optical coupling system is in the interior of the tapered disc.
17. The optical system of claim 16 , wherein the light redirecting element is a curved reflector that is configured to emit redirected light along substantially radial directions within the tapered disc.
18. An optical system comprising:
a means for coupling light, the light coupling means including:
a light input surface configured to receive incident light through an input aperture; and
a light output surface configured to emit the incident light through an output aperture having an area smaller than an area of the input aperture,
wherein the light coupling means is configured to couple to a means for emitting light, the light emitting means being separated from the light input surface by a gap, the gap including a medium having lower refractive index than the refractive index of material forming the light coupling means; and
a means for receiving light, the light receiving means being optically coupled to the light output surface of the light coupling means, the light receiving means including:
a means for redirecting light, the light redirecting means being configured to receive light from the light output surface of the light coupling means along an incident direction and redirect the light along an output direction that is at an angle with respect to the incident direction; and
a means for guiding light configured to internally propagate the redirected light,
wherein a material of the light receiving means that is optically coupled with the output aperture has substantially the same refractive index as material of the light coupling means, and
wherein the light coupling means is configured to preserve etendue of the light emitted from the output surface relative to the etendue of light incident on the input surface of the light coupling means.
19. The optical system of claim 18 , wherein the light coupling means includes an optical coupling system, the light receiving means includes a light receiving system and the light guiding means includes a light guide.
20. The optical system of claim 18 , wherein a ratio of the area of the input aperture to the area of the output aperture is approximately n 2 , where n is the refractive index of the material forming the light coupling means.
21. A method of manufacturing an optical system, the method comprising:
providing an optical coupling system including:
a light input surface configured to receive incident light through an input aperture; and
a light output surface configured to emit the incident light through an output aperture having an area smaller than an area of the input aperture,
wherein the optical coupling system is configured to couple to an optical source separated from the light input surface by a gap, the gap including a medium having lower refractive index than the refractive index of material forming the optical coupling system; and
providing an optical receiving system optically coupled to the light output surface of the optical coupling system, the optical receiving system including:
a light redirecting element configured to receive light from the light output surface of the optical coupling system along an incident direction and redirect the light along an output direction that is at an angle with respect to the incident direction; and
a light guide configured to internally propagate the redirected light,
wherein a material of the optical receiving system optically coupling with the output aperture has substantially the same refractive index as material of the optical coupling system, and
wherein the optical coupling system is configured to preserve etendue of the light emitted from the output surface relative to the etendue of light incident on the input surface of the optical coupling system.
22. The method of claim 21 , wherein a ratio of the area of the input aperture to the area of the output aperture is approximately n 2 , where n is the refractive index of the material forming the optical coupling system.