Compact lighting system and display device

• US 20050231976A1
• Filed: 12/05/2002
• Published: 10/20/2005
• Est. Priority Date: 12/07/2001
• Status: Active Grant

• Current Assignee: Philips Lumileds Lighting Company LLC (Apollo Global Management, Inc.)
• Original Assignee: Philips Lumileds Lighting Company LLC (Apollo Global Management, Inc.)
• Inventors: Hendriks, Robert Frans Maria, Keuper, Matthijs Hendrik
• Granted Patent: US 7,364,343 B2
• Time in Patent Office: Days
• US Class Current: 362/600
• 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

Abstract

A compact backlight system for illuminating a display device (12) has a light-emitting panel (1) with a front wall (2) and an opposed rear wall (3) and with edge surfaces (4, 5). At least one of the edge surfaces (4) is light-transmitting. The backlight system has a light source (6) comprising a limited number of LEDs. Light from the light source (6) is coupled into the light-emitting panel (1) via the edge surface that is light-transmitting. According to the invention, the light-emitting panel (1) is wedge-shaped, and the surface area S_i of the light-transmitting edge surface (4) and the surface area S_r of the opposite edge surface (5) fulfill the relation: 1<(S_r/S_i)<10, preferably 1.5<(S_r/S_i)<5. Light travelling for the first time from the light-transmitting edge surface through the light-emitting panel (1) towards the opposite edge surface (5) cannot be coupled out of the light emitting panel (1).

Claims

1. A lighting system provided with a light-emitting panel comprising:

a front wall, a rear wall situated opposite thereto, and furthermore edge surfaces between said front wall and said rear wall wherein;

at least one of said edge surfaces of the panel is light-transmitting,

at least one light source is associated with the light-transmitting edge surface,

light originating from the light source is incident on the light-transmitting edge surface and distributes itself in the panel during operation,

the light-emitting panel widens from the light-transmitting edge surface in a direction towards an edge surface situated opposite said light-transmitting edge surface, and

a ratio of a surface area S_i of the light-transmitting edge surface to a surface area S_r of the edge surface situated opposite the light-transmitting edge surface satisfies;

$1<<br><br>\frac{S_r}{S_i}<<br><br>10.$

2. A lighting system as claimed in claim 1, wherein the ratio S_r/S_i satisfies:

$1.5<<br><br>\frac{S_r}{S_i}<<br><br>5.$

3. A lighting system as claimed in claim 2, wherein the ratio S_r/S_i satisfies:

$2.5<<br><br>\frac{S_r}{S_i}<<br><br>4.$

4. A lighting system as claimed in claim 1, wherein the edge surface situated opposite the light-transmitting edge surface is reflecting with respect to light inside the light-emitting panel.

5. A lighting system as claimed in claim 4, wherein the edge surface situated opposite the light-transmitting edge surface is diffusely reflecting or is provided with a diffusely reflecting material.

6. A lighting system as claimed in claim 1, wherein the edge surface situated opposite the light-transmitting edge surface is faceted.

7. A lighting system as claimed in claim 1, wherein the front wall and the light-transmitting edge surface enclose in side elevation of the light-emitting panel an obtuse angle with a value 90+β

in which β

is a tilt angle over which the light-transmitting edge surface is tilted with respect to a normal of the front wall.

8. A lighting system as claimed in claim 7, wherein at a position of the light-transmitting edge surface the front wall and the rear wall enclose a wedge angle α

, and wherein the tilt angle β

at least has a value of 0.5*α

for α

≧

1°

.

9. A lighting system as claimed in claim 7, wherein β

≧

α

for α

≧

0.3°

.

10. A lighting system as claimed in claim 9, wherein the rear wall is free of reflecting material in a region adjacent the light-transmitting edge surface.

11. A lighting system as claimed in claim 7, wherein β

≧

1.5−

1.4*α

for α

≦

0.5°

.

12. A lighting system as claimed in claim 7, wherein β

≧

1.5−

1.4*α

for α

≦

0.5°

.

13. A lighting system as claimed in claim 1, wherein the rear wall of the light-emitting panel is diffusely reflecting or is provided with a diffusely reflecting material.

14. A lighting system as claimed in claim 13, wherein the reflecting material is positioned slightly apart with an air gap from the respective edge surface opposite the light-transmitting edge surface and rear wall.

15. A lighting system as claimed in claim 1, wherein the light source comprises at least two light-emitting diodes with different light emission wavelengths.

16. A lighting system as claimed in claim 15, wherein each of the light-emitting diodes has a luminous flux of at least 5 lm.

17. A display device provided with a lighting system as claimed in claim 1.

18. A display device as claimed in claim 17, which display device comprises a liquid crystal display.