Lighting apparatus having low profile

• US 6,473,554 B1
• Filed: 09/24/1997
• Issued: 10/29/2002
• Est. Priority Date: 12/12/1996
• Status: Expired due to Term

• Current Assignee: Seoul Semiconductor Co., Ltd.
• Original Assignee: Teledyne Lighting & Display Products, Inc. (Teledyne Technologies Incorporated)
• Inventors: Pelka, David G., Popovich, John
• Primary Examiner(s): NGO, HUNG NHAT
• Application Number:
  US08/936,717
• Time in Patent Office: 1,861 Days
• Field of Search: 362/555, 362/559, 362/560, 362/561, 385/146, 385/901, 385/14
• US Class Current: 385/146
• CPC Class Codes: G02B 6/0018 Redirecting means on the surface of the light guide
• CPC Class Codes: G02B 6/0021 for housing at least a part of the light source, e.g. by forming holes or recesses
• CPC Class Codes: G02B 6/0038 Linear indentations or grooves, e.g. arc-shaped grooves or meandering grooves, extending over the full length or width of the light guide
• CPC Class Codes: G02B 6/0046 Tapered light guide, e.g. wedge-shaped light guide
• CPC Class Codes: G02B 6/0055 Reflecting element, sheet or layer
• CPC Class Codes: G02B 6/006 to produce indicia, symbols, texts or the like
• CPC Class Codes: G02B 6/0061 to provide homogeneous light output intensity
• CPC Class Codes: G04B 19/30 Illumination of dials or hands dials in general G04B19/06; moving indicating means with numbers or hands, in general G04B19/20; arrangements for indicating different local apparent times by means of a globe illuminated from inside G04B19/22; continuous indication of the time by non-electric light sources G04B25/00, e.g. by electric lamps G04C17/02; illumination by electric lamps which function at fixed times or periodically G04C19/02; illuminated panels G09F13/00
• CPC Class Codes: Y10S 385/901 Illuminating or display apparatus

Abstract

Disclosed is a low profile lighting apparatus that is particularly advantageous for use as a backlight for illuminating a display. The lighting apparatus includes a waveguide coupled to a light source for injecting light into the waveguide. The waveguide includes a plurality of elongate structures for ejecting light propagating within the waveguide through a predetermined surface of the waveguide. Another embodiment of the waveguide includes a central region of reduced thickness that redirects light propagating within the waveguide. The lighting apparatus has a low profile so it is particularly useful in areas of limited space.

Claims

1. An illumination device, comprising:

a waveguide having an illumination coupler embedded in an interior region of said waveguide, said illumination coupler adapted to receive light from a point source within said interior region, and to direct light between generally parallel top and bottom surfaces outside said interior region, said illumination coupler comprising a refractive index interface which is inclined relative to at least one of said top and bottom surfaces said interface being configured to reflect light rays emitted by the point source which propagate along a line that forms less than the critical angle of total internal reflection with respect to a line lying in one of said top and bottom surfaces, such that light rays which would otherwise pass out of said waveguide are captured for propagation between said top and bottom surfaces.

2. The illumination device of claim 1, wherein said illumination coupler comprises a surface configured for total internal reflection of light incident thereon.

3. The illumination device of claim 2, comprising a point source of light disposed at least partially within a cavity in said waveguide, said cavity being adjacent to said total internal reflecting surface.

4. The illumination device of claim 3, comprising display elements on one of said top and bottom surfaces for ejecting light from said waveguide.

5. The illumination device of claim 3, comprising diffusive reflective material on one of said top and bottom surfaces.

6. The illumination device of claim 1, wherein the waveguide and illumination coupler are integrally formed from a single piece of material.

7. An illumination device comprising, in combination,

a) a waveguide for light, and defining a substantially flat light travel channel,

b) an LED closely associated with the waveguide,

c) and there being a surface on the waveguide curving toward the LED to receive impingement of light from the LED, said surface being a TIR surface with respect to said impingement of light from the LED, for re-directing such light to travel along said light travel channel, said surface defining a cusp directed toward the LED, said LED having an end terminating in alignment with said cusp to direct substantially all light from the LED directly toward and adjacent the cusp.

8. The device of claim 7 wherein said LED has a light-emitting portion located within a boundary defined by said waveguide.

9. The device of claim 7 wherein said waveguide has a body and said surface is concave adjacent the waveguide body.

10. The device of claim 7 wherein said surface is concave toward said channel.

11. The device of claim 7 wherein said surface defines an axis directed toward the LED.

12. The device of claim 11 wherein said surface defines an axis that intersects said cusp and said LED.

13. The device, as defined in claim 7, and comprising:

said waveguide is an optical waveguiding layer;

and including display elements formed on said waveguiding layer to cause light to be emitted from said waveguiding layer.

14. The device of claim 13, wherein:

said display elements are formed as concave channels within the surface of the waveguiding layer, and external surfaces of said channels are either smooth or rough to promote diffuse output radiation.

15. The device of claim 14, wherein:

said concave channels of said display elements have depths across said waveguiding layer that compensate for differences in said illumination.

16. The device of claim 15, wherein:

said concave channels of said display elements are deeper towards outer portions on said waveguiding layer of said display device than are said concave channels towards central portions of said waveguiding layer of said display device.

17. The device of claim 13, wherein:

each of said display elements is a polygon solid having an apex or a vertex on a line normal to said waveguiding layer.

18. The device of claim 13, wherein:

each of said display elements has the form of a polygon solid having two or more equilateral side faces.

19. The device of claim 13, including:

a lens element incorporated integrally to the surface of said waveguiding layer.

20. The device of claim 13, wherein:

said waveguiding layer has an overall shape that is thin relative to its length.

21. The device of claim 13, wherein:

said display elements are arranged in alphanumeric patterns.

22. The device of claim 13, wherein:

said LED is a bullet lens package light emitting diode.

23. The device of claim 13, wherein:

there is an air gap formed between said LED and said waveguiding layer.

24. The device of claim 13, wherein:

said LED is embedded in said waveguiding layer by optically coupling said LED to said waveguiding layer with an optical coupling agent.

25. The device of claim 24, wherein:

said optical coupling agent is one of the following;

a silicone adhesive, gel, grease, an epoxy polymer.

26. The device of claim 13, wherein:

said display elements are concentric circular grooves in a surface of the waveguiding layer, said concentric circular grooves being present only in areas corresponding to symbolic or nonsymbolic characters.

27. The device of claim 7, wherein:

said display elements are retroreflective corner cube elements.

28. An optical apparatus, comprising:

an LED;

an optical element having generally parallel top and bottom opposing sides and an edge extending between the top and bottom opposing sides, said LED mounted at a predetermined location adjacent a central portion of one of said opposing sides such that light from the LED enters the optical element, said optical element including a TIR surface spaced from said one opposing side and extending from a point adjacent the predetermined location of the LED outwardly towards said edges such that said light entering the optical element is directed against said TIR surface, said TIR surface curving in the vicinity of the LED so as to form a cusp adjacent the LED, the curving TIR surface having a curvature which totally internally reflects light rays incident on said TIR surface and redirects such light rays through said optical element, whereby such light rays do not pass through the other opposing surface.

29. The apparatus of claim 28, wherein the cusp is in the form of an equiangular spiral.

30. An optical apparatus, comprising:

a light emitting diode (LED);

an optical element having top and bottom opposing sides and an edge extending between the top and bottom opposing sides, said LED mounted at a predetermined location beneath a central portion of said optical element such that light from the LED enters the optical element, said optical element including a TIR surface spaced from said bottom side and extending from a point above the LED outwardly towards said edges, said TIR surface positioned to receive light emitted by the LED, said TIR surface curving towards the LED so as to form a cusp above the LED, the curving TIR surface totally internally reflecting light rays such that reflected light rays propagate from the TIR surface towards the edge of the optical element.

31. The optical apparatus of claim 30, wherein said TIR surface is circularly symmetric.

32. The optical apparatus of claim 31, wherein said TIR surface has a vortex-like shape.

33. The optical apparatus of claim 30, wherein said TIR surface is leaky such that some light emitted by the LED is transmitted therethrough.

34. The optical apparatus of claim 33, wherein said cusp is contoured to permit leakage of light through said TIR surface.

35. The optical apparatus of claim 34, wherein said cusp is rounded to permit leakage of light through said TIR surface.

36. The optical apparatus of claim 30, wherein said optical element comprises polymeric material.

37. The optical apparatus of claim 36, wherein said optical element comprises material selected from the group comprising acrylic, polycarbonate, and silicone.

38. An optical apparatus, comprising:

a light emitting diode (LED);

an optical element positioned to receive light from the light emitting diode, said element comprised of a refractive index interface having a curved shape that is symmetrical about an axis and converges to a location in a central portion of the optical element, said location and said light emitting diode lying substantially on said axis, said interface being shaped and positioned relative to said LED to reflect a substantial portion of light from said LED in a direction transverse to said axis.

39. The optical apparatus of claim 38, wherein said refractive index interface is circularly symmetric.

40. The optical apparatus of claim 39, wherein said curved shape conforms to the shape of a vortex.

41. The optical apparatus of claim 38, wherein said refractive interface surface converges to form a cusp which terminates at said location.

42. The optical apparatus of claim 41, wherein said cusp is contoured to permit leakage of light through said central portion of said refractive index interface.

43. The optical apparatus of claim 42, wherein said cusp is rounded to permit leakage of light through said central portion of said refractive index interface.

44. The optical apparatus of claim 38, wherein said refractive index interface has a shape of an equiangular spiral.

45. The optical apparatus of claim 38, wherein said refractive index interface is leaky such that some light emitted by the light emitting diodes transmitted therethrough.

46. The optical apparatus of claim 38, wherein said optical element comprises polymeric material.

47. The optical apparatus of claim 46, wherein said optical element comprises material selected from the group comprising acrylic, polycarbonate, and silicone.

48. The optical apparatus of claim 46, wherein said refractive index interface comprises an air/polymer interface.