LIGHTING DEVICE

• US 20150355505A1
• Filed: 02/11/2013
• Published: 12/10/2015
• Est. Priority Date: 02/10/2012
• Status: Active Grant

• Current Assignee: Top Victory Investments Limited (Nanjing Huadong Electronics Information & Technology Co., Ltd.)
• Original Assignee: TP Vision Holding BV (Nanjing Huadong Electronics Information & Technology Co., Ltd.)
• Inventors: Cornelissen, Hugo Johan, Langendijk, Erno Hermanus Antonius, Overes, Theodorus Franciscus Emilius, Onac, Gabriel Eugen
• Granted Patent: US 9,488,863 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G02B 6/0043 provided on the surface of the light guide
• CPC Class Codes: G02B 6/0073 Light emitting diode [LED]
• CPC Class Codes: G02B 6/0075 Arrangements of multiple light guides G02B6/0028 takes precedence
• CPC Class Codes: G02F 1/133603 with LEDs
• CPC Class Codes: G02F 1/133606 including a specially adapted diffusing, scattering or light controlling members
• CPC Class Codes: G02F 1/133611 including means for improving the brightness uniformity

Abstract

The present disclosure relates to a backlight for illuminating back lit displays (e.g. LC displays of LCD televisions). In order to enable a thin design of the backlight and a high uniformity of the light emitted by the backlight, an apparatus may be provided with transparent and diffusing masking elements that may mask individual light sources and may diffuse light back into a light guide. Absorbing elements and/or retro-reflective elements may be arranged proximate the light sources in order to avoid generation of bright spots or rings around the light sources.

Claims

1. A lighting device, comprising:

one or more planar light guides, wherein each of the one or more planar light guides includes a respective back face for receiving light and a respective front face for emitting light,

one or more light sources arranged to transmit light into the respective back face of the one or more planar light guides,

one or more semi-transparent masking elements, wherein each of the one or more semi-transparent masking elements having a respective light diffusing surface arranged to partially diffuse light back into the one or more light guides and partially transmit light through a respective semi-transparent masking element so as to mask the one or more light sources, and

one or more light absorbers arranged adjacent to the one or more light sources to absorb at least a fraction of light diffused from the respective diffusing surface of the one or more semi-transparent masking elements, or one or more retro-reflectors arranged adjacent to the one or more light sources to reflect at least a fraction of light diffused from the respective diffusing surface of the one or more semi-transparent masking elements back to an adjacent one of the one or more semi-transparent masking elements, wherein the one or more light absorbers or the one or more retro-reflectors are not optically connected to the one or more planar light guides.

2. A lighting device according to claim 1, wherein the one or more light absorbers or the one or more retro-reflectors are separated from the one or more light guides by air or by a transparent material with a low refractive index.

3. A lighting device according to claim 2, wherein the one or more light sources are connected to the one or more light guides by a transparent adhesive having a refractive index that is higher than the refractive index of a transparent adhesive connecting the one or more light absorbers or the one or more retro-reflectors.

6. A lighting device according to claim 1, further comprising out coupling features arranged at a surface of the front face, a surface of the back face of the one or more light guides, or inside the one or more light guides for coupling light out through the front face at non-masked locations wherein the one or more semi-transparent masking element is not present.

7. A lighting device according to claim 1, wherein the one or more light sources are mechanically connected to the one or more light absorbers or the one or more retro-reflectors, and wherein the one or more light absorbers, the one or more retro-reflectors, and/or the one or more light sources are fixed to the back face.

11. A lighting device according to claim 1, further comprising a light diffusing or reflective surface facing the back face of the one or more light guides and arranged next to the one or more light absorbers or the one or more retro-reflectors, for diffusing or reflecting light transmitted through the back face back into the one or more light guides.

12. A lighting device according to claim 6, wherein the light out coupling capability of the out coupling features and a transparency of the one or more semi-transparent masking elements is configured to equalize light intensity of light coupled out by the out coupling features and light transmitted by the one or more semi-transparent masking elements.

4. (canceled)

5. (canceled)

8. (canceled)

9. (canceled)

10. (canceled)

13. (canceled)

14. A method for illuminating a matrix of image forming transparent pixels of a display, the method comprises providing a lighting device which comprises

a planar light guide with a back face for receiving light and a front face for emitting light,

first and second light sources arranged to transmit light into the back face of the light guide,

first and second semi-transparent masking elements having light diffusing surfaces, where the masking elements are arranged to partially diffuse light back into the light guide and partially transmit light through the masking elements so as to mask the respective first and second light sources, and

first and second absorbers arranged adjacent to the respective first and second light sources to absorb at least a fraction of light diffused from the diffusing surfaces of the respective first and second masking elements, or first and second retro-reflectors arranged adjacent to the respective first and second light sources to reflect at least a fraction of light diffused from the diffusing surfaces of the respective first and second masking elements back to the respective first and second masking elements, the method further comprises,

arranging the matrix of image forming transparent pixels in front of the plate shaped light guide.

15. A method according to claim 14, wherein the first and second light sources are connected to the first and second light guides by a transparent adhesive having a refractive index that is higher than the refractive index of a transparent adhesive connecting the first and second light absorbers or the first and second retro-reflectors.

16. A method according to claim 14, further comprising out coupling features-arranged at a surface of the front face, a surface of the back face of the first and second light guides, or inside the first and second light guides for coupling light out through the front face at non-masked locations wherein the first and second semi-transparent masking element is not present.

17. A method according to claim 14, wherein the first and second light sources are mechanically connected to the first and second light absorbers or the first and second retro-reflectors, and wherein the first and second light absorbers, the first and second retro-reflectors, and/or the first and second light sources are fixed to the back face.

18. A method according to claim 14, further comprising:

providing a light diffusing or reflective surface facing the back face of the first and second light guides and arranged next to the first and second light absorbers or the first and second retro-reflectors, for diffusing or reflecting light transmitted through the back face back into the first and second light guides.

19. A method according to claim 16, wherein the light out coupling capability of the out coupling features and a transparency of the first and second semi-transparent masking elements is configured to equalize light intensity of light coupled out by the out coupling features and light transmitted by the first and second semi-transparent masking elements.

20. A method according to claim 16, wherein the one or more light absorbers or the one or more retro-reflectors are separated from the one or more light guides by air or by a transparent material with a low refractive index.

21. A display for showing images, comprising:

a matrix of image forming transparent pixels; and

a lighting device arranged such that a front face of the lighting device faces a face of the matrix of image forming transparent pixels, wherein the lighting device comprises;

one or more planar light guides, wherein each of the one or more planar light guides includes a respective back face for receiving light and a respective front face for emitting light;

one or more light sources arranged to transmit light into the respective back face of the one or more planar light guides;

one or more semi-transparent masking elements, wherein each of the one or more semi-transparent masking elements having a respective light diffusing surface arranged to partially diffuse light back into the one or more light guides and partially transmit light through a respective semi-transparent masking element so as to mask the one or more light sources; and

one or more light absorbers arranged adjacent to the one or more light sources to absorb at least a fraction of light diffused from the respective diffusing surface of the one or more semi-transparent masking elements, or one or more retro-reflectors arranged adjacent to the one or more light sources to reflect at least a fraction of light diffused from the respective diffusing surface of the one or more semi-transparent masking elements back to an adjacent one of the one or more semi-transparent masking elements,

wherein the one or more light absorbers or the one or more retro-reflectors are not optically connected to the one or more planar light guides and wherein the one or more light absorbers or the one or more retro-reflectors are separated from the one or more light guides by air or by a transparent material with a low refractive index.

22. A display according to claim 21, wherein the one or more light sources are connected to the one or more light guides by a transparent adhesive having a refractive index that is higher than the refractive index of a transparent adhesive connecting the one or more light absorbers or the one or more retro-reflectors.

23. A display according to claim 21, further comprising out coupling features-arranged at a surface of the front face, a surface of the back face of the one or more light guides, or inside the one or more light guides for coupling light out through the front face at non-masked locations wherein the one or more semi-transparent masking element is not present.

24. A display according to claim 21, wherein the one or more light sources are mechanically connected to the one or more light absorbers or the one or more retro-reflectors, and wherein the one or more light absorbers, the one or more retro-reflectors, and/or the one or more light sources are fixed to the back face.

25. A display according to claim 21, further comprising a light diffusing or reflective surface facing the back face of the one or more light guides and arranged next to the one or more light absorbers or the one or more retro-reflectors, for diffusing or reflecting light transmitted through the back face back into the one or more light guides.

26. A display according to claim 23, wherein the light out coupling capability of the out coupling features and a transparency of the one or more semi-transparent masking elements is configured to equalize light intensity of light coupled out by the out coupling features and light transmitted by the one or more semi-transparent masking elements.