Illumination system using light emitting diodes
Publication Date: 2002-Sep-28
The IP.com Prior Art Database
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The purpose of the system is to provide a uniform illumination onto a target. This target can be close to the system, like in an LCD display, and the system is configured as a backlight, or the system can be on the ceiling or wall of a room, and provide a uniform illumination in the room or on a desk. The system consists of a fixture, and red, green and blue LEDs. The LEDs are preferably of a side emitting type, like the ones produced by Lumileds, called Luxeon™ side emitters (Luxeon codes LXHL-Dxxx, see http://www.luxeon.com), or are regular LEDs, or the Luxeon Lambertian or batwing devices, and have an optical structure mounted in front of the LEDs to spread the light to the side. As an alternative, the LEDs can be mounted on a post, so that the light is mainly directed to the side. The fixture is configured as a box, where the thickness of the box is in general smaller than its width and height. In general it will be of a rectangular shape, but any other shape can be made as well (disk). In most cases the box will be made of metal, and the insides of the box will be covered by high reflecting (reflection coefficient > 75%) sheets (either white diffuse, of a mirror type). These sheets can be shaped to improve the uniformity of the illumination, and to improve the efficiency of the fixture. On the front side of the fixture (the output side), transmissive plastic sheets can be used, either of a diffuse type, or having a optical microstructure, to spread the light into the desired directions. An example of such a film is a brightness enhancement film, as produced by 3M (BEF).