Colored lighting device

• US 20020097354A1
• Filed: 01/16/2002
• Published: 07/25/2002
• Est. Priority Date: 01/20/2001
• Status: Active Grant

• Current Assignee: Signify Holding B.V. (Signify N.V.)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Greiner, Horst
• Granted Patent: US 7,063,430 B2
• Time in Patent Office: Days
• US Class Current: 349/61
• CPC Class Codes: F21S 10/02 changing colors F21S10/002 - F21S10/007, F21S10/04 take precedence
• CPC Class Codes: F21Y 2105/10 comprising a two-dimensional array of point-like light-generating elements
• CPC Class Codes: F21Y 2113/13 comprising an assembly of point-like light sources
• CPC Class Codes: F21Y 2115/10 Light-emitting diodes [LED]
• CPC Class Codes: G02B 6/0011 the light guides being planar or of plate-like form
• CPC Class Codes: G02F 1/133603 with LEDs

Abstract

A lighting device for generating mixed colors is described, which device comprises a light emission surface (11) and a plurality of light sources (21) such as, for example, LEDs of different colors, and which device is suitable in particular for backlighting of 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 into which a plurality of cavities (20) are recessed, each cavity accommodating a light source (21) and having an upper side (203) which faces the light emission surface (11) and side walls (201), which upper side (203) is coated with a first reflecting layer (204), while the coupling of light into the optical waveguide plate takes place through the side walls (201). A very homogeneous mixing and distribution of the light from each individual light source on the light emission surface is achieved thereby.

Claims

1. A lighting device for generating mixed colors, which device comprises a light emission surface and a plurality of light sources of different colors, characterized by an optical waveguide plate (1) into which a plurality of cavities (20) is provided, each cavity (20) accommodating a light source (21), and each cavity (20) having an upper side (203) facing the light emission surface (11) and side walls (201), said upper side (203) being coated 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) extend substantially perpendicularly to the light emission surface (11), and the upper sides (203) of the cavities (20) extend substantially parallel to the light emission surface (11).

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

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

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) comprise a plurality of red, green, and blue light-emitting diodes which are distributed such that no light sources of the same color lie in mutually adjoining cavities (20).

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) is prolonged by a first portion (204a) in horizontal direction into the optical waveguide plate (1).

10. A lighting device as claimed in claim 1, characterized in that the first reflecting layer (204) is prolonged by 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) lying opposite the upper side (203) are surrounded by a third reflecting layer (205).

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