Optical element for lateral light spreading in edge-lit displays and system using same

• US 20060290844A1
• Filed: 06/24/2005
• Published: 12/28/2006
• Est. Priority Date: 06/24/2005
• Status: Active Grant

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Weber, Michael F., Epstein, Kenneth A.
• Granted Patent: US 8,023,065 B2
• Time in Patent Office: Days
• US Class Current: 349/113
• CPC Class Codes: G02F 1/133615 Edge-illuminating devices, i.e. illuminating from the side
• CPC Class Codes: G02F 1/133617 Illumination with ultraviolet light; Luminescent elements or materials associated to the cell
• CPC Class Codes: G02F 1/13362 providing polarized light, e.g. by converting a polarisation component into another one

Abstract

An illumination light unit has at least one light source that generates illumination light. The unit also includes a reflecting cavity having one or more reflectors and a controlled transmission mirror disposed at an output of the reflecting cavity. The controlled transmission mirror includes an input coupling element, an output coupling element and a first multilayer reflector disposed between the input and output coupling elements. At least some of the illumination light is reflected within the reflecting cavity by the one or more reflectors and is transmitted out of the reflecting cavity through the controlled transmission mirror. The illumination light unit may be used for generating light for space lighting, or for illuminating a display. For example, the unit may be used in a backlight to illuminate a lightguide placed behind a display panel.

Claims

1. An optical system, comprising:

an image-forming panel having an illumination side and a viewing side;

a light guide disposed to the illumination side of the image-forming panel; and

an illumination light unit comprising one or more light sources capable of generating illumination light and a controlled transmission mirror arranged to receive the illumination light from the one or more light sources, the controlled transmission mirror comprising an input coupling element, an output coupling element and a first multilayer reflector disposed between the input and output coupling elements, the input coupling element redirecting at least some of the illumination light incident thereon in a direction substantially perpendicular to the first multilayer reflector into a direction that is transmitted through the multilayer reflector to the output coupling element, illumination light from the output coupling element being coupled into the light guide.

2. A system as recited in claim 1, wherein the image-forming panel is a liquid crystal display (LCD) panel, and further comprising a first polarizer disposed on the viewing side of the LCD panel and a second polarizer disposed on the illumination side of the LCD panel.

3. A system as recited in claim 1, further comprising a controller coupled to control an image displayed by the image-forming panel.

4. A system as recited in claim 1, wherein the one or more light sources comprise light emitting diodes (LEDs).

5. A system as recited in claim 1, wherein the one or more light sources comprise a first light source that emits light at a first wavelength and a second light source that emits light at a second wavelength different from the first wavelength.

6. A system as recited in claim 1, wherein the illumination light unit further comprises a reflective surface disposed to reflect light from the one or more light sources to the controlled transmission mirror.

7. A system as recited in claim 6, wherein the illumination light unit comprises a reflective cavity, the one or more light sources being positioned to emit light within the reflective cavity.

8. A system as recited in claim 1, wherein the first multilayer reflector comprises a polymeric multilayer film.

9. A system as recited in claim 1, wherein the input coupling element comprises at least one of a bulk diffuser, a surface diffuser and a structured surface.

10. A system as recited in claim 1, wherein the output coupling element comprises at least one of a bulk diffuser, a surface diffuser and a structured surface.

11. A system as recited in claim 1, wherein the controlled transmission mirror further comprises a transparent layer disposed between the input coupling element and the output coupling element.

12. A system as recited in claim 11, wherein the transparent layer is disposed between the first multilayer reflector and the output coupling element.

13. A system as recited in claim 11, wherein the first multilayer reflector is disposed between the transparent layer and the output coupling element.

14. A system as recited in claim 11, further comprising a side reflector disposed at at least one edge of the transparent layer to reflect light that would escape from the transparent layer in the absence of the side reflector.

15. A system as recited in claim 1, wherein the output coupling element couples light out of the controlled transmission mirror in substantially only one polarization state.

16. A system as recited in claim 15, wherein the output coupling element comprises a disperse polymeric phase in a continuous polymeric matrix, at least one of the disperse polymeric phase and the continuous polymeric matrix comprising birefringent polymeric material.

17. A system as recited in claim 15, wherein the output coupling element comprises fibers disposed within a polymeric matrix, at least one of the fibers and the polymeric matrix comprising birefringent polymeric material.

18. A system as recited in claim 1, further comprising one or more light management films disposed between the light guide and the image-forming panel.

19. A system as recited in claim 18, wherein the one or more light management films comprise at least one of a reflective polarizer and a brightness enhancing film, and further comprising a reflector, the light guide being disposed between the reflector and the one or more light management films.

20. A system as recited in claim 1, further comprising a wavelength converter disposed on an optical path of light within the optical system to convert wavelength of light emitted by the one or more light sources.

21. A system as recited in claim 20, wherein the wavelength converter is disposed between the controlled transmission mirror and the lightguide.

22. An illumination light unit, comprising:

at least a first light source capable of generating illumination light; and

a reflecting cavity having one or more reflectors and a controlled transmission mirror disposed at an output of the reflecting cavity, the controlled transmission mirror comprising an input coupling element, an output coupling element and a first multilayer reflector disposed between the input and output coupling elements, at least some of the illumination light from the at least a first light source being reflected within the reflecting cavity by the one or more reflectors and being transmitted out of the reflecting cavity through the controlled transmission mirror.

23. A unit as recited in claim 22, wherein the controlled transmission mirror further comprises a transparent layer disposed between the input and output coupling elements.

24. A unit as recited in claim 22, wherein the at least a first light source comprises a light emitting diode (LED).

25. A unit as recited in claim 22, wherein the at least a first light source comprises at least a first light source and a second light source, the first light source generating light at a first wavelength and the second light source generating light at a second wavelength different from the first wavelength.

26. A unit as recited in claim 22, further comprising a light wavelength converter disposed to convert the wavelength of the illumination light output through the controlled transmission mirror.

27. A unit as recited in claim 22, wherein the reflecting cavity is elongated along a longitudinal axis and has a first end, and the controlled transmission mirror is on a first side of the reflecting cavity, substantially parallel to the longitudinal axis.

28. A unit as recited in claim 27, wherein the at least a first light source is disposed at the first end of the reflecting cavity.

29. A unit as recited in claim 27, wherein the at least a first light source is disposed on a second side of the reflecting cavity.

30. A unit as recited in claim 22, wherein the reflecting cavity comprises at least one curved reflector on an optical path between the one or more light sources and the controlled transmission mirror.

31. A unit as recited in claim 30, wherein the at least one curved reflector is curved in one dimension only.

32. A unit as recited in claim 30, wherein the at least one curved reflector comprises at least two curved reflectors, each of the curved reflectors curved in two dimensions.