Lighting device with point-shaped light sources

• US 20020097578A1
• Filed: 01/16/2002
• Published: 07/25/2002
• Est. Priority Date: 01/20/2001
• Status: Active Grant

• Current Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Greiner, Horst
• Granted Patent: US 6,964,497 B2
• Time in Patent Office: Days
• US Class Current: 362/240
• CPC Class Codes: G02B 6/0021 for housing at least a part of the light source, e.g. by forming holes or recesses
• CPC Class Codes: G02B 6/0055 Reflecting element, sheet or layer
• CPC Class Codes: G02F 1/133603 with LEDs

Abstract

A lighting device is described which comprises a light emission surface (11) and a plurality of substantially point-shaped light sources (21) such as, for example, LEDs, and which is suitable in particular for backlighting liquid crystal displays such as LCD picture screens, or for use as a planar light radiator. The lighting device is characterized in particular in that an optical waveguide plate (1) is provided with a plurality of cavities (20) for the light sources (21), which cavities are covered with a first reflecting layer (204) on their upper sides (203) facing the light emission surface (11), while the coupling of the light into the optical waveguide plate takes place through side walls (201) of the cavities. A very homogeneous distribution of the luminous intensity on the light emission surface is achieved thereby.

Claims

1. A lighting device which comprises a light emission surface and a plurality of substantially point-shaped light sources, and which is characterized by an optical waveguide plate (1) into which a plurality of cavities (20) is provided, each cavity (20) accommodating a light source (21), which cavities each comprise an upper side (203) facing the light emission surface (11) and side walls (201), said upper side (203) being covered with a first reflecting layer (204), while the coupling of the light into the optical waveguide plate takes place through the side walls (201).

2. A lighting device as claimed in claim 1, characterized in that the side walls (201) of the cavities (20) are substantially perpendicular to the light emission surface (11), and the upper sides (203) of the cavities (20) are substantially parallel to the light emission surface (11).

3. A lighting device as claimed in claim 1, characterized in that the cavities (20) are each covered with a second reflecting layer (121) on their lower side opposite to their upper side (203).

4. A lighting device as claimed in claim 1, characterized in that the cavities (20) are substantially cylindrical in shape.

5. A lighting device as claimed in claim 1, characterized in that the cavities (20) are provided in the lower side (12) of the optical waveguide plate (1).

6. A lighting device as claimed in claim 1, characterized in that the light sources (21) are light-emitting diodes.

7. A lighting device as claimed in claim 3, characterized in that the second reflecting layer (121) extends over the side faces (13 to 16) and the lower side (12) of the optical waveguide plate (1).

8. A lighting device as claimed in claim 7, characterized in that the second reflecting layer (121) is at a distance from the optical waveguide plate (1), which distance constitutes an air gap.

9. A lighting device as claimed in claim 1, characterized in that the first reflecting layer (204) extends further in horizontal direction with a first portion (204a) into the optical waveguide plate (1).

10. A lighting device as claimed in claim 1, characterized in that the first reflecting layer (204) extends further with a second portion (204b) along the side walls (201) of the cavity (20).

11. A lighting device as claimed in claim 1, characterized in that the edges of the cavities (20) situated opposite the upper side (203) are surrounded by a third reflecting layer (205).

12. A liquid crystal display device with a lighting device as claimed in any one of the preceding claims.