NVIS compatible backlight device and LCD using the same
View Patent ↗A backlight device for a liquid crystal display containing a substantially planar light guide with a light emission surface and a light-collecting portion opposing the light emission surface. A pair of opposing side portions may define the periphery of the light guide. A first plurality of LEDs are placed so as to direct the emitted light into the light-collecting portion. An NVIS filter is preferably placed adjacent to at least one of the side portions. A second plurality of LEDs are placed to direct the emitted light through the NVIS filter and into a side portion of the light guide. Alternative embodiments can contain NVIS filters and LEDs along additional edge portions of the light guide. Some embodiments may use directing elements or slanted surfaces of the light guide to direct the light from the second plurality of LEDs into the edge portions of the light guide.
1. A backlight device for a liquid crystal display comprising:
a substantially planar light guide comprising:
a light emission surface;
a light-collecting portion opposing the light emission surface;
four edge portions defining a periphery of the planar light guide;
a first plurality of LEDs positioned within a first plane in a direct-lit orientation and arranged to direct the emitted light from the first plurality of LEDs into the light-collecting portion;
a first NVIS filter placed adjacent to the light guide; and
a second plurality of LEDs positioned within the first plane and near an edge portion, arranged to direct the emitted light from the second plurality of LEDs through the NVIS filter and into the light guide.
2. The backlight device of claim 1 further comprising:
a second NVIS filter placed adjacent to the light guide; and
a third plurality of LEDs positioned within the first plane and near an edge portion opposite the edge portion containing the second plurality of LEDs, and arranged to direct the emitted light from the third plurality of LEDs through the second NVIS filter and into the light guide.
3. The backlight device of claim 1 further comprising:
a directing element placed adjacent to the second plurality of LEDs which directs the emitted light from the second plurality of LEDs through the first NVIS filter and into the light guide.
4. The backlight device of claim 1 further comprising:
a mounting structure attached to both the first and second plurality of LEDs.
5. The backlight device of claim 1 further comprising:
light scattering features within the light guide.
6. A backlight device comprising:
a light guide plate comprising
a light emission surface,
a saw-tooth surface opposing the light emission surface and defined by a plurality of alternating substantially vertical sub-surfaces and slanted sub-surfaces,
four edge portions defining a periphery of the planar light guide;
a first plurality of LEDs arranged to direct the emitted light from the first plurality of LEDs through the substantially vertical sub-surfaces;
a first NVIS filter placed adjacent to one of the edge portions; and
a second plurality of LEDs arranged to direct the emitted light from the second plurality of LEDs through the NVIS filter and into the edge portion of the light guide plate.
7. The backlight device of claim 6 wherein:
the NVIS filter is a hot mirror filter.
8. The backlight device of claim 6 further comprising:
a second NVIS filter placed adjacent to the edge portion opposite the edge portion which contains the first NVIS filter; and
a third plurality of LEDs arranged to direct the emitted light from the third plurality of LEDs through the second NVIS filter and into the edge portion of the light guide.
9. The backlight device of claim 6 wherein:
the substantially vertical sub-surfaces have a curved profile.
10. The backlight device of claim 6 further comprising:
a directing element placed adjacent to the second plurality of LEDs which directs the emitted light from the second plurality of LEDs through the first NVIS filter and into the light guide.
11. The backlight device of claim 10 further comprising:
a mounting structure attached to both the first and second plurality of LEDs.
12. The backlight device of claim 6 further comprising:
light scattering particles within the light guide.
13. A backlight device comprising:
a light guide plate comprising
a light emission surface,
a saw-tooth surface opposing the light emission surface and defined by a plurality of alternating substantially vertical sub-surfaces, substantially horizontal sub-surfaces, and slanted sub-surfaces,
a first pair of opposing edges which are substantially parallel to the substantially vertical sub-surfaces, and
a second pair of opposing edges which are substantially orthogonal to the first pair of opposing edges;
a first plurality of LEDs arranged to direct the emitted light from the first plurality of LEDs through the substantially vertical sub-surfaces;
a NVIS filter placed adjacent to one of the second pair of opposing edges of the light guide; and
a second plurality of LEDs arranged adjacent to the NVIS filter with at least one LED adjacent to each substantially horizontal sub-surface to direct the emitted light from the second plurality of LEDs through the NVIS filter and into the light guide plate.
14. The backlight device of claim 13 further comprising:
a mounting structure attached to both the first and second plurality of LEDs.
15. The backlight device of claim 13 wherein:
the substantially vertical sub-surfaces have a curved profile.
16. The backlight device of claim 13 further comprising:
light scattering features within the light guide.
17. A backlight device for a liquid crystal display comprising:
a substantially planar light guide comprising:
a light emission surface;
a light-collecting surface opposing the light emission surface;
four edge portions defining a periphery of the light guide, at least one of the edge portions comprising:
a substantially horizontal surface extending outwardly from the light-collecting surface and
a slanted surface connecting the substantially horizontal surface with the light emission surface;
a first plurality of LEDs arranged to direct the emitted light from the first plurality of LEDs into the light-collecting portion;
a NVIS filter placed adjacent to the substantially horizontal surface; and
a second plurality of LEDs arranged to direct the emitted light from the second plurality of LEDs through the NVIS filter and onto the slanted surface.
18. The backlight device of claim 17 wherein:
the slanted surface is reflective.
19. The backlight device of claim 17 wherein:
the first plurality of LEDs are oriented so as to emit the strongest light in the vertical direction.
20. A backlight device for a liquid crystal display comprising:
a substantially planar light guide comprising:
a light emission surface;
a light-collecting surface opposing the light emission surface;
four edge surfaces defining a periphery of the planar light guide;
a mounting structure placed adjacent to the light-collecting surface and substantially parallel to the planar light guide;
a first plurality of LEDs placed on the mounting structure to direct the emitted light from the first plurality of LEDs vertically into the light-collecting portion;
a NVIS filter placed adjacent to one of the edge portions;
a directing element placed adjacent to the NVIS filter; and
a second plurality of LEDs placed on the mounting structure and below the directing element so that the emitted light from the second plurality of LEDs reflects off the directing element, through the NVIS filter, and into the edge portion of the light guide.