Compact lighting system and display device

• US 7,364,343 B2
• Filed: 12/05/2002
• Issued: 04/29/2008
• Est. Priority Date: 12/07/2001
• Status: Expired due to Term

• Current Assignee: Philips Lumileds Lighting Company LLC (Apollo Global Management, Inc.)
• Original Assignee: Philips Lumileds Lighting Company LLC (Apollo Global Management, Inc.)
• Inventors: Keuper, Matthijs Hendrik, Hendriks, Robert Frans Maria
• Primary Examiner(s): Truong; Bao Q
• Application Number:
  US10/497,481
• Publication Number:
  US 20050231976A1
• Time in Patent Office: 1,972 Days
• Field of Search: 362/26, 362/27, 362600-634, 362559-561, 349 61- 67, 405/46, 405/47
• US Class Current: 362/628
• 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 a reflecting edge surface situated opposite said light-transmitting edge surface, the reflecting edge surface situated opposed said light-transmitting edge surface being planar, and

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

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

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

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

6. The 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.

7. The lighting system as claimed in claim 6, 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°

.

8. The lighting system as claimed in claim 7 wherein β

≧

α

for α

≧

0.3°

.

9. The lighting system as claimed in claim 8, wherein the rear wall is free of reflecting material in a region adjacent the light-transmitting edge surface.

10. The lighting system as claimed in claim 7 wherein β

≧

1.5-1.4*α

for α

≧

0.5°

.

11. The lighting system as claimed in claim 7 wherein β

≧

1.5-1.4*α

for α

≧

0.5°

.

12. The 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.

13. The lighting system as claimed in claim 12, wherein the reflecting material is positioned slightly apart with an air gap between the reflecting material and rear wall.

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

15. The lighting system as claimed in claim 14, wherein each of the light-emitting diodes has a luminous flux of at least 5 lm.

16. A display device provided with the lighting system as claimed in claim 1.

17. The display device as claimed in claim 16, which display device comprises a liquid crystal display.