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10 April 2005 Etendue efficient coupling of an array of LEDs for projection display
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The rapid development of high power visible LEDs has prompted an increase in interest in the projection display industry. Although the power level has not achieved sufficient level for large projection displays, it is sufficient for smaller displays. It is also expected that in the near future, there will be significant improvements in the LED output and the market may open up. In this paper, a LED based illumination engine is presented which is suitable for projection display using an array of LEDs whose output is coupled into a single light pipe with minimum loss of brightness. The basic building block in the array consists of an LED chip mounted on a heat conductive substrate, a concave reflector, and a tapered light pipe. The concave reflector can be spherical, toroidal, elliptical, or dual paraboloidal. The LED light is focused at the input of the tapered light pipe by the concave reflector. The output dimension of the light pipe is made so that it has the same cross-sectional size of the building block, and therefore, the array of tapered light pipes are packed tightly at the output end without lost space in between. This will allow the most efficient way to combine the light output without loss in etendue. Various configuration of this system will be shown below that is applicable to projections displays.
© (2005) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Kenneth Li and Seiji Inatsugu "Etendue efficient coupling of an array of LEDs for projection display", Proc. SPIE 5740, Projection Displays XI, (10 April 2005);


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