Directional backlights with light emitting element packages
View Patent ↗A light emitting diode package for a directional display may comprise light emitting diodes and a protection diode. The protection diode may be arranged in a well that is at a different location to the well that the light emitting diodes are arranged. The directional display may include a waveguide. The waveguide may include light extraction features arranged to direct light from an array of light sources by total internal reflection to an array of viewing windows and a reflector arranged to direct light from the waveguide by transmission through extraction features of the waveguide to the same array of viewing windows. The brightness of the directional display can be increased. An efficient and bright directional display system can be achieved. Efficient light baffling for light escaping from the edge of the waveguide is achieved through light deflecting extraction films.
1. A directional backlight for a directional display apparatus, comprising:
an array of light sources;
a waveguide comprising an input end arranged to receive input light from the array of light sources at respective input positions, and first and second, opposed guide surfaces for guiding input light along the waveguide, the second guide surface being arranged to deflect light as output light through the first guide surface;
an input end, front light shielding arrangement for shielding the light sources, comprising:
an extraction film strip extending across the first guide surface adjacent the input end, the extraction film strip comprising an array of alternating first and second facets, the first facets being oriented to receive light that leaks from the first guide surface while being guided along the waveguide, and the second facets being arranged to deflect the received light towards the normal to the first guide surface; and
a mask arranged outside the extraction film strip arranged to absorb the received light after deflection by the second facets; and
an input end, rear light shielding arrangement for shielding the light sources comprising:
an extraction film strip extending across the second guide surface adjacent the input end, the extraction film strip comprising an array of alternating first and second facets, the first facets being oriented to receive light that leaks from the second guide surface while being guided along the waveguide and the second facets being arranged to deflect the received light towards the normal to the second guide surface; and
a mask arranged outside the extraction film strip arranged to absorb the received light after deflection by the second facets.
2. A directional backlight according to claim 1 , wherein at least one of:
the extraction film strip of the input end, front light shielding arrangement, and
the extraction film strip of the input end, rear light shielding arrangement is absorptive for absorbing at least pan of the received light.
3. A directional backlight according to claim 1 , wherein the waveguide further comprises a reflective end for reflecting input light back through the waveguide, the second guide surface being arranged to deflect light after reflection from the reflective end as said output light.
4. A directional backlight according to claim 3 , further comprising a reflective end, front light shielding arrangement for shielding the light sources, comprising:
an extraction film strip extending across the first guide surface adjacent the reflective end, the extraction film strip comprising an array of alternating first and second facets, the first facets being oriented to receive lion that leaks from the first guide surface while being guided along the waveguide, and the second facets being arranged to deflect the received light towards the normal to the first guide surface; and
a mask arranged outside the extraction film snip arranged to absorb the received light after deflection by the second facets.
5. A directional backlight according to claim 4 , further comprising a reflective end, rear light shielding arrangement for shielding the light sources, comprising:
an extraction film strip extending across the second guide surface adjacent the reflective end, the extraction film strip comprising an army of alternating first and second facets, the first facets being oriented to receive light that leaks from the second guide surface while being guided along the waveguide and the second facets being arranged to deflect the received light towards the normal to the first guide surface; and
a mask arranged outside the extraction film strip arranged to absorb the received light after deflection by the second facets.
6. A directional backlight according to claim 5 , wherein at least one of the masks of:
the input end, front light shielding arrangement,
the input end, rear light shielding arrangement,
the reflective end, front light shielding arrangement, and
the reflective end, rear light shielding arrangement is a layer formed on the outside surface of the extraction film strip.
7. A directional backlight according to claim 1 , wherein the first guide surface is arranged to guide light by total internal reflection and the second guide surface comprises a plurality of light extraction features oriented to direct light guided through the waveguide in directions allowing exit through the first guide surface as the output light and intermediate regions between the light extraction features that are arranged to guide light through the waveguide.
8. A directional backlight according to claim 1 , wherein
the first guide surface is arranged to guide light by total internal reflection and the second guide surface is substantially planar and inclined at an angle to direct, light in directions that break that total internal reflection for outputting light through the first guide surface, and
the directional display apparatus further comprises a deflection element extending across the first guide surface of the waveguide for deflecting light towards the normal to the first guide surface.
9. A directional display apparatus comprising:
a directional backlight according to claim 1 ; and
a transmissive spatial light modulator arranged to receive the output light from the first guide surface of the waveguide and to modulate it to display an image.
10. A directional display apparatus according to claim 9 , wherein the mask of the input end, front light shielding arrangement is a portion of the spatial light modulator.
11. A directional backlight tor a directional display apparatus, comprising:
an array of light sources;
a waveguide comprising an input end arranged to receive input light from the array of light sources at respective input positions, and first and second, opposed guide surfaces for guiding input light along the waveguide, the second guide surface being arranged to deflect light as output light through the first guide surface;
a first extraction film strip extending across at least a portion of the first guide surface, the extraction film strip comprising a first array of alternating first and second facets, the first array of first facets being oriented to receive light that leaks from the first guide surface while being guided along the waveguide, and the first, array of second facets being arranged to deflect the received light towards the normal to the first guide surface;
a first mask arranged outside the first extraction film strip arranged to absorb the received light after deflection by the first array of second facets;
a second extraction film strip extending across at least a portion of the second guide surface, the extraction film strip comprising a second array of alternating first and second facets, the second array of first facets being oriented to receive light that leaks from the second guide surface while being guided along the waveguide and; the second array of second facets being arranged to deflect the received light towards the normal to the second guide surface; and
a second mask arranged outside the second extraction film strip arranged to absorb the received light after deflection by the second array of second facets.
12. A directional backlight according to claim 11 , wherein the waveguide further comprises a reflective end for reflecting input light back through the waveguide, the second guide surface being arranged to deflect light after reflection from the reflective end as said output light.
13. A directional backlight according to claim 12 , wherein at least one of the first and second extraction strips is adjacent to the reflective end of the waveguide.
14. A directional backlight according to claim 13 , wherein one of the first and second extraction strips is adjacent to the reflective end of the waveguide, and the other of the first and second extraction strips is adjacent to the input end of the waveguide.
15. A directional backlight according to claim 11 , wherein for at least one of the first and second arrays of first alternating first and second facets, ridges between respective pairs of the alternating first and second facets extend in a direction orthogonal to the normal to an input-end surface of the waveguide and orthogonal to the normal to the first guide surface.
16. A directional backlight for a directional display, apparatus, comprising:
an array of light sources;
a waveguide comprising an input end arranged to receive input, light from the array of light sources at respective input positions, and first and second, opposed guide surfaces for guiding input light along the waveguide, the second guide surface being arranged to deflect light as output light through the first guide surface;
a front light shielding arrangement for shielding the light sources, the front light shielding arrangement extending across at least a portion of the first guide surface, the a front light shielding arrangement comprising a first array of alternating first and second facets, the first array of first facets being oriented to receive light that leaks from the first guide surface while being guided along the waveguide, and the first array of second facets being arranged to deflect the received light towards the normal to the first guide surface, the front light shielding arrangement being configured to absorb the received light after deflection by the first array of second facets; and
a rear light shielding arrangement for shielding the light sources, the rear light shielding arrangement extending across at least a portion of the second guide surface, the rear light shielding arrangement comprising a second array of alternating first and second facets, the second array of first facets being oriented to receive light that leaks from the second guide surface while being guided along the waveguide and the second array of second facets being arranged to deflect the received light towards the normal to the second guide surface, the rear light shielding arrangement being configured to absorb the received light after deflection by the second array of second facets.
17. A directional backlight according to claim 16 , wherein the waveguide further comprises a reflective end for reflecting input light back through the waveguide, the second guide surface being, arranged to deflect, light after reflection from the reflective end as said output light.
18. A directional backlight according to claim 17 , wherein at least a portion of at least one of the front and rear light shielding arrangements is adjacent to the reflective end of the waveguide.
19. A directional backlight according to claim 18 , wherein at least a portion of one of the front and rear light shielding arrangements is adjacent to the reflective end of the waveguide, and the other of the front and rear light shielding arrangements is adjacent to the input end of the waveguide.
20. A directional backlight according to claim 16 , wherein for at least one of the first and second arrays of first alternating first and second facets, ridges between respective pairs of the alternating first and second facets extend in a direction orthogonal to the normal to an input-end surface of the waveguide and orthogonal to the normal to the first guide surface.