Elimination of stitch artifacts in a planar illumination area

• US 7,907,804 B2
• Filed: 11/26/2008
• Issued: 03/15/2011
• Est. Priority Date: 12/19/2007
• Status: Active Grant

• Current Assignee: Oree Advanced Illumination Solutions Ltd.
• Original Assignee: Oree, Inc.
• Inventors: Zimmermann, Micha, Meir, Noam, Shani, Yosi
• Primary Examiner(s): Rahll; Jerry T
• Application Number:
  US12/324,555
• Publication Number:
  US 20090162015A1
• Time in Patent Office: 839 Days
• Field of Search: 385/31, 349/63, 349/65, 362/616, 362/628
• US Class Current: 385/31
• CPC Class Codes: G02B 6/0065 Manufacturing aspects; Material aspects
• CPC Class Codes: G02B 6/0068 Arrangements of plural sources, e.g. multi-colour light sources
• CPC Class Codes: G02B 6/0073 Light emitting diode [LED]
• CPC Class Codes: G02B 6/008 of the partially overlapping type
• CPC Class Codes: G02B 6/0088 of the light guide or other optical sheets in the package

Abstract

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.

Claims

1. A planar illumination area comprising:

a first discrete light-guide element comprising (i) a first light source emitting light therein, (ii) first and second adjacent non-parallel sidewalls spanning top and bottom surfaces, and (iii) a first out-coupling region in the top surface; and

a second discrete light-guide element in contact with the first discrete light-guide element and comprising (i) a second light source, different from the first light source, emitting light therein, (ii) first and second adjacent non-parallel sidewalls spanning top and bottom surfaces, and (iii) a second out-coupling region in the top surface, only a portion of the second out-coupling region, including at least one sidewall of the second light-guide element, being disposed over and overlapping only a portion of the first out-coupling region including at least one sidewall of the first light-guide element, to define an overlapping region having an area,

wherein (i) a light output power of the first out-coupling region within the overlapping region is less than a light output power of the first out-coupling region outside the overlapping region and (ii) a light output power of the second out-coupling region within the overlapping region is less than a light output power of the second out-coupling region outside the overlapping region, whereby the overlapping region emits a substantially uniform light output power over the area.

2. The planar illumination area of claim 1, wherein the light output power of the overlapping region differs from the light output power of the first and second out-coupling regions outside the overlapping region by no more than 10%.

3. The planar illumination area of claim 2, wherein the change in light output power between the overlapping region and the first and second out-coupling regions outside the overlapping region is gradual.

4. The planar illumination area of claim 1, wherein the first out-coupling region comprises light-scattering elements therein, a density of the light-scattering elements disposed within the first out-coupling region outside the overlapping region being greater than a density of the light-scattering elements disposed within the first out-coupling region inside the overlapping region.

5. The planar illumination area of claim 4, wherein the density of the light-scattering elements inside the overlapping region decreases along one direction.

6. The planar illumination area of claim 1, wherein the second out-coupling region is transparent in the overlapping region so as not to augment light emitted from the first out-coupling region.

7. The planar illumination area of claim 6, wherein, in the overlapping region, light emitted from the first out-coupling region passes through the second out-coupling region.

8. The planar illumination area of claim 1, further comprising a third discrete light-guide element comprising a third out-coupling region in its top surface, only a portion of the third out-coupling region overlapping only a second portion of the second out-coupling region to define a second overlapping region different from the overlapping region and having a second area, wherein the second overlapping region emits a substantially uniform light output power over the second area.

9. The planar illumination area of claim 1, wherein at least a portion of the first sidewall of the first light-guide element (i) is non-vertical and (ii) forms a non-right angle with at least one of the top or bottom surfaces of the first light-guide element, and at least a portion of the first sidewall of the second light-guide element (i) is non-vertical, (ii) forms a non-right angle with at least one of the top or bottom surfaces of the second light-guide element, and (iii) is complementary to the first sidewall of the first light-guide element, the first sidewalls of the first and second light-guide element being disposed beneath a top surface of the second light-guide element in the overlapping region.

10. The planar illumination area of claim 9, wherein a top surface of the planar illumination area comprises the top surfaces of the first and second light-guide elements and is substantially flat.

11. The planar illumination area of claim 1, further comprising additional discrete light-guide elements forming, with the first and second 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.

12. The planar illumination area of claim 1, further comprising additional discrete light-guide elements forming, with the first and second light-guide elements, an array extending in first and second non-parallel directions, wherein the light-guide elements overlap in the first and second directions.

13. The planar illumination area of claim 1, wherein the overlapping region comprises a light-absorbing material.

14. The planar illumination area of claim 1, wherein at least a portion of a sidewall of the first light-guide element comprises a reflective coating.

15. The planar illumination area of claim 1, wherein at least a portion of a sidewall of the second light-guide element comprises a reflective coating.

16. The planar illumination area of claim 1, wherein only a portion of a top surface of at least one of the first light-guide element or the second light-guide element is a light-absorbing surface.

17. A method of forming a planar illumination area, the method comprising:

providing a first discrete light-guide element comprising (i) a first light source emitting light therein, (ii) first and second non-parallel sidewalls spanning top and bottom surfaces, and (iii) a first out-coupling region in the top surface; and

disposing beneath and overlapping only a portion of the first light-guide element with a second discrete light-guide element comprising (i) a second light source, different from the first light source, emitting light therein, (ii) first and second non-parallel sidewalls spanning top and bottom surfaces, and (iii) a second out-coupling region in the top surface, thereby forming an overlapping region comprising only a portion of the first out-coupling region including at least one sidewall of the first light-guide element and only a portion of the second out-coupling region including at least one sidewall of the second light-guide element,

wherein (i) a light output power of the first out-coupling region within the overlapping region is less than a light output power of the first out-coupling region outside the overlapping region and (ii) a light output power of the second out-coupling region within the overlapping region is less than a light output power of the second out-coupling region outside the overlapping region, whereby the overlapping region emits a substantially uniform light output power.

18. A planar illumination area comprising:

a first discrete light-guide element comprising a polished sidewall disposed between a top surface and a bottom surface of the first light-guide element; and

a second discrete light-guide element comprising a polished sidewall disposed between a top surface and a bottom surface of the second light-guide element, the polished sidewall of the second light-guide element being adjacent to the polished sidewall of the first light-guide element,

wherein the second light-guide element receives light from the first light-guide element through the polished sidewalls, and light is refracted as it travels from the first light-guide element to the second light-guide element.

19. The planar illumination area of claim 18, further comprising an index-matching material located between the sidewalls, an index of refraction of the index-matching material being approximately equal to an index of refraction of at least one of the first light-guide element or the second light-guide element.

20. The planar illumination area of claim 18, wherein the first and second polished sidewalls are polished to a tolerance less than approximately 600 nm peak-to-peak.

21. A planar illumination area comprising:

a first discrete light-guide element comprising a sidewall disposed between a light-emitting top surface and a bottom surface of the first light-guide element;

a second discrete light-guide element comprising a sidewall disposed between a light-emitting top surface and a bottom surface of the second light-guide element, the first and second light-guide elements being butted together or only partially overlapping such that their light-emitting top surfaces collectively form a single continuous illumination surface including at least one of the sidewalls; and

an index-matching material covering the sidewalls, an index of refraction of the index-matching material being approximately equal to an index of refraction of at least one of the first light-guide element or the second light-guide element,

wherein light travels between the first and second light-guide elements, and, in a direction of travel from the first light-guide element to the second light-guide element, an intensity of light emitted by the continuous illumination surface changes continuously and monotonically notwithstanding the included sidewalls.

22. The planar illumination area of claim 21, wherein the sidewall of the second light-guide element is adjacent to the sidewall of the first light-guide element and the index-matching material is located between the sidewalls.

23. The planar illumination of claim 21, wherein the first and second light-guide elements only partially overlap, and the index-matching material is disposed over and in direct contact with the first and second light-guide elements to create a smooth surface thereover.