Compact lighting system and display device

• US 7,172,328 B2
• Filed: 03/27/2003
• Issued: 02/06/2007
• Est. Priority Date: 04/25/2002
• Status: Expired due to Fees

• Current Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Hoelen, Christoph Gerard August, Pfeffer, Nicola Bettina
• Primary Examiner(s): Ward; John Anthony
• Assistant Examiner(s): MAKIYA, DAVID J
• Application Number:
  US10/511,972
• Publication Number:
  US 20050140849A1
• Time in Patent Office: 1,412 Days
• Field of Search: 362/610, 362/615, 362/616, 362/619, 362623-626, 362/628
• US Class Current: 362/610
• CPC Class Codes: F21Y 2105/00 Planar light sources
• CPC Class Codes: F21Y 2115/10 Light-emitting diodes [LED]
• 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

Abstract

A compact backlight system has a light-emitting panel (1) with a front wall (2), a rear wall (3) situated opposite thereto, and furthermore, between the front and the rear wall (2, 3), a translucent input edge surface (4) for coupling light into the light-emitting panel (1). A light source (6, 6′, . . . ) is associated with the input edge surface (4). According to the invention, the rear wall (3) in a first portion (12) of the light-emitting panel (1) is provided with a multiplicity of steps (13, 13′, . . . ), and a second portion (22) of the light-emitting panel (1) widens from the input edge surface (4) in a direction facing the first portion (12). Preferably, a surface (17) of the steps (13, 13′, . . . ) facing the input edge surface (4) makes an angle β_av≧5° (with respect to a normal on a bisecting plane (20) bisecting the light-emitting panel (1).

Claims

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

a front wall (2), a rear wall (3) situated opposite thereto, and furthermore, between the front and the rear wall (2, 3), a translucent input edge surface (4) for coupling light into the light-emitting panel (1),

while at least a light source (6, 6′

, . . . ) is associated with the input edge surface (4), and

while, in operation, light originating from the light source (6, 6′

, . . . ) is incident on the input edge surface (4) and distributes itself in the light-emitting panel (1), characterized

in that the rear wall (3) in a first portion (12) of the light-emitting panel (1) is provided with a multiplicity of steps (13, 13′

, . . . ), and

in that a second portion (22) of the light-emitting panel (1) widens from the input edge surface (4) in a direction facing the first portion (12)

characterized in that a surface (17) of the steps (13, 13′

, . . . ) facing the input edge surface (4) makes an average angle β

_av with respect to a normal (25) on a bisecting plane (20) bisecting the light-emitting panel (1),

wherein the bisecting plane (20) comprises a bisecting line (21) in the input edge surface (4), said bisecting line (21) being parallel to the front wall (2) and bisecting the input edge surface (4), and

wherein the average angle β

_av is in the range 5≦

β

_av≦

25°

.

2. A lighting system as claimed in claim 1, characterized in that the surface (17) of the steps (13, 13′

, . . . ) facing the input edge surface (4) comprises a specular reflector (31) on a side facing away from the input edge surface (4).

3. A lighting system as claimed in claim 1, characterized in that the steps (13, 13′

, . . . ) comprise a diffuser (32) on a side facing away from the light-emitting panel (1) while an air gap (33) is maintained between the steps (13, 13′

, . . . ) and the diffuser (32).

4. A lighting system as claimed in claim 1, characterized in that the height h_st of a step (13, 13′

, . . . ) is in the range 0.1≦

h_st≦

0.5 mm.

5. A lighting system as claimed in claim 1, characterized in that the distance d_st between two steps (13, 13′

, . . . ) is in the range 0.1≦

d_st≦

10 mm.

6. A lighting system as claimed in claim 1, characterized in that the number of steps (13, 13′

, . . . ) is in the range from 25 to 100.

7. A lighting system as claimed in claim 1, characterized in that the length l_fp of the first portion (12) as compared to the length l_fw of the front wall (2) is in the range 0.05≦

l_fp/l_fw≦

0.6.

8. A lighting system as claimed in claim 1, characterized in that the ratio of the surface area S_es of the input edge surface (4) to the surface area S_tr in the lightemitting panel (1) at the transition between the first portion (12) and the second portion (22) of the light-emitting panel (1) satisfies the relation 1<

S_tr/S_es<

10.

9. A lighting system as claimed in claim 8, characterized in that the ratio is 1.5<

S_tr/S_es<

4.

10. A lighting system as claimed in claim 1, characterized in that the front wall (2) is provided with a translucent diffuser (8).

11. A lighting system as claimed in claim 1, characterized in that the front wall (2) is provided with a light redirecting foil.

12. A lighting system as claimed in claim 1, characterized in that the light source (6, 6′

, . . . ) comprises at least one white LED or at least two lightemitting diodes with different light emission wavelengths.

13. A lighting system as claimed in claim 12, characterized in that each of the light-emitting diodes has a luminous flux of at least 5 lm.

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

15. A display device as claimed in claim 14, which display device comprises a liquid crystal display (50).