Micro-structured illumination system for providing polarized light
A multi-layered arrangement according to the invention provide emission of polarized light. At least one of the interfacing surfaces between the layers is provided with a microstructure. In one embodiment, a first layer in the form of a lightguide substrate ( 401 ) receives unpolarized light from a lamp ( 420 ). A birefringent second layer ( 402 ) is provided with a microstructure ( 410 ) in the form of parallel grooves. On top of the birefringent layer a third layer ( 403 ), i.e. a coating layer, is located. Light is outcoupled by way of selective Total Internal Reflection, TIR, at the micro-structured surface of the birefringent layer, yielding a highly linearly polarized emission at near normal angles. The polarized light may be emitted out through the coating or in an opposite direction through the lightguide, which in an advantageous manner allow any configuration of transmissive (backlight), transflective (backlight) or reflective (frontlight) display arrangement.
1. An arrangement comprising:
a lightguide that is configured to receive unpolarized light,
a birefringent layer that is optically coupled to the lightguide and configured to provide polarized light, and includes a substantially planar surface and an opposite facing interface surface, and
an interface layer that is located between the lightguide and the interface surface of the birefringent layer,
wherein
the birefringent layer and the interface layer are coupled via a polarization-selective microstructure.
2. The arrangement of claim 1 , wherein
the interface layer includes an adhesive.
3. The arrangement of claim 1 , further including
a display panel that is configured to receive the polarized light.
4. The arrangement of claim 1 , wherein
the birefringent layer includes the microstructure, and the interface layer fills grooves in the microstructure.
5. The arrangement of claim 4 , wherein the birefringent layer includes an embossed PET.
6. The arrangement of claim 1 , wherein
the microstructure is configured to facilitate emission of the polarized light at an angle that is substantially normal to a surface of the arrangement.
7. The arrangement of claim 1 , wherein
the microstructure is configured to facilitate emission of the polarized light from the birefringent layer in a direction away from the lightguide.
8. The arrangement of claim 1 , wherein
the microstructure is configured to facilitate emission of the polarized light from the birefringent layer in a direction toward the lightguide.
9. The arrangement of claim 1 , wherein
the birefringent layer includes a first refraction index and a second refraction index, and
the interface layer has an index of refraction that substantially matches the first refraction index of the birefringent layer.
10. The arrangement of claim 9 , wherein
the interface layer is isotropic.
11. The arrangement of claim 1 , wherein
the birefringent layer includes a first refraction index and a second refraction index, and
the lightguide has an index of refraction that is less than the first and second indices of refraction of the birefringent layer.
12. The arrangement of claim 1 , wherein
the birefringent layer includes a first refraction index and a second refraction index, and
the lightguide has an index of refraction that is between the first and second indices of refraction of the birefringent layer.
13. An arrangement comprising:
a lightguide that is configured to receive unpolarized light,
a birefringent layer that is optically coupled to the lightguide and configured to provide polarized light, and
an interface layer that is located between the lightguide and the interface surface of the birefringent layer,
wherein
the birefringent layer and the interface layer are coupled via a polarization-selective microstructure, and the interface layer includes the microstructure, and the birefringent layer fills grooves in the microstructure.
14. The arrangement of claim 13 , wherein
the birefringent layer includes a liquid crystal polymer.
15. An arrangement comprising:
a lightguide that is configured to receive unpolarized light,
a birefringent layer that is optically coupled to the lightguide and configured to provide polarized light, and
a third layer,
wherein
the birefringent layer is located between the lightguide and the third layer,
the birefringent layer and the third layer are coupled via a polarization-selective microstructure, and
the microstructure is configured to refract the polarized light so as to the polarized light is emitted through the lightguide.
16. The arrangement of claim 15 , wherein
the microstructure is configured so that the polarized light is emitted at an angle that is substantially normal to a surface of the apparatus.
17. The arrangement of claim 15 , further including
a display panel that is configured to receive the polarized light.
18. The arrangement of claim 15 , wherein
the birefringent layer includes a first refraction index and a second refraction index, and
the third layer has an index of refraction that substantially matches the first refraction index of the birefringent layer.
19. The arrangement of claim 18 , wherein
the third layer is anisotropic.
20. The arrangement of claim 15 , wherein
the birefringent layer includes a first refraction index and a second refraction index, and
the lightguide has an index of refraction that is less than the first and second indices of refraction of the birefringent layer.