Elimination of stitch artifacts in a planar illumination area
In one aspect, a planar illumination area includes two light-guide elements, each with an out-coupling region. At least a portion of each out-coupling region overlaps with at least a portion of the other. The overlapping region emits a substantially uniform light output power.
1. A planar illumination area substantially free of stitch artifacts, comprising:
a first discrete light-guide element comprising (i) first and second non-parallel sidewalls spanning top and bottom surfaces, the first sidewall being reflective, and (ii) an out-coupling region partially bounded by the sidewalls;
a second discrete light-guide element comprising (i) first and second non-parallel sidewalls spanning top and bottom surfaces, the first sidewall being reflective, and (ii) an out-coupling region partially bounded by the sidewalls, the first sidewall of the second light-guide element being adjacent and opposed to the first sidewall of the first light-guide element; and
a third discrete light-guide element comprising an out-coupling region, at least a portion of the out-coupling region of the third light-guide element overlapping at least a portion of the out-coupling region of the first light-guide element, including the second sidewall thereof, to define an overlapping region having an area,
wherein (i) light in the first light-guide element striking its first sidewall substantially reflects therefrom rather than travelling into the second light-guide element, (ii) light in the second light-guide element striking its first sidewall substantially reflects therefrom rather than travelling into the first light-guide element, and (iii) the overlapping region emits a substantially uniform light output over the area.
2. The planar illumination area of claim 1 , further comprising a gap between the first light-guide element and the third light-guide element in the overlapping region.
3. The planar illumination area of claim 2 , wherein at least one of the first light-guide element or the third light-guide element comprises a light-absorbing surface in the overlapping region.
4. The planar illumination area of claim 1 , further comprising a diffuser sheet disposed over the first, second, and third light-guide elements.
5. The planar illumination area of claim 1 , wherein the light output power of the overlapping region differs from the light output power of the out-coupling regions of the first and third light-guide elements by no more than 10%.
6. The planar illumination area of claim 5 , wherein a change in light output power between the out-coupling regions of the first and third light-guide elements along the overlapping region is gradual.
7. The planar illumination area of claim 1 , wherein the out-coupling region of the first light-guide element comprises light-scattering elements therein and the out-coupling regions of the first and third light-guide elements overlap only partially, a density of the light-scattering elements disposed within the out-coupling region of the first light-guide element outside the overlapping region being greater than a density of the light-scattering elements disposed within the out-coupling region of the first light-guide element inside the overlapping region.
8. The planar illumination area of claim 7 , wherein the density of the light-scattering elements inside the overlapping region decreases along one direction.
9. The planar illumination area of claim 1 , wherein the out-coupling region of the third light-guide element is transparent in the overlapping region.
10. The planar illumination area of claim 9 , wherein, in the overlapping region, light emitted from the out-coupling region of the first light-guide element passes through the out-coupling region of the third light-guide element.
11. The planar illumination area of claim 1 , wherein the second sidewall of the first light-guide element is non-vertical, and the third light-guide element comprises a complementary non-vertical sidewall spanning top and bottom surfaces within the overlapping region, the second sidewall of the first light-guide element and the complementary sidewall of the third light-guide element being disposed beneath the top surface of the third light-guide element in the overlapping region.
12. The planar illumination area of claim 11 , wherein a top surface of the planar illumination area comprising the top surfaces of the first and third light-guide elements is substantially flat.
13. The planar illumination area of claim 1 , further comprising additional discrete light-guide elements forming, with the first, second, and third light-guide elements, an array extending in first and second non-parallel directions, wherein the light-guide elements overlap in the first direction and do not overlap in the second direction.
14. The planar illumination area of claim 1 , wherein the first sidewalls of the first and second light-guide elements are polished.
15. The planar illumination area of claim 14 , wherein the first sidewalls of the first and second light-guide elements are polished to a tolerance less than approximately 600 nm peak-to-peak.
16. The planar illumination area of claim 1 , wherein the first sidewalls of the first and second light-guide elements have a reflective coating thereon.
17. The planar illumination area of claim 1 , wherein the first and second sidewalls of the first light-guide element are perpendicular to the top and bottom surfaces of the first light-guide element, and the first and second sidewalls of the second light-guide element are perpendicular to the top and bottom surfaces of the second light-guide element.
18. The planar illumination area of claim 17 , wherein the first and second sidewalls of the first light-guide element form right angles to the top and bottom surfaces of the first light-guide element, and the first and second sidewalls of the second light-guide element form right angles with the top and bottom surfaces of the second light-guide element.
19. A planar illumination area substantially free of stitch artifacts, comprising:
a first discrete light-guide element comprising (i) first and second non-parallel sidewalls spanning top and bottom surfaces, the first sidewall being polished, and (ii) an out-coupling region partially bounded by the sidewalls;
a second discrete light-guide element comprising (i) first and second non-parallel sidewalls spanning top and bottom surfaces, the first sidewall being polished, and (ii) an out-coupling region partially bounded by the sidewalls, the first sidewall of the second light-guide element being adjacent to the first sidewall of the first light-guide element without overlap therebetween; and
a third discrete light-guide element comprising an out-coupling region, at least a portion of the out-coupling region of the third light-guide element overlapping at least a portion of the out-coupling region of the first light-guide element, including the second sidewall thereof, to define an overlapping region having an area,
wherein (i) light in the first light-guide element striking its first sidewall refracts and travels into the second light-guide element through its first sidewall, and (ii) the overlapping region emits a substantially uniform light output over the area.