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20 August 2005 High-efficiency LED backlight optics designed with the flow-line method
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A novel backlight concept suitable for LED's has been designed using the flow-line design method, which allows controlling both the illumination uniformity and light extraction without scattering the light. This contrasts with conventional LED backlight optical designs, which are based on the use of a light guide with Lambertian scattering features that break the guidance and extract the light. Since most of Lambertian scattered light is re-guided, the average ray path in conventional backlights is long and multiple bounces are needed, which may lead to low efficiency. On the other hand, the new design presented here is not only efficient but also provide a relatively high collimation of the output beam (an output beam within a 10 degrees half-angle cone, with total theoretical efficiency over 80% including Fresnel and absorption losses). Wider beams can be controlled by design or obtained by adding a holographic diffuser at the exit. The new design offers other very interesting practical features: it can be very thin, can be made transparent (which widens its applications, including front lighting), can mix the colors from several LED's or recover reflected polarization for LCD illumination.
© (2005) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Juan C. Minano, Pablo Benitez, Julio Chaves, Maikel Hernandez, Oliver Dross, and Asuncion Santamaria "High-efficiency LED backlight optics designed with the flow-line method", Proc. SPIE 5942, Nonimaging Optics and Efficient Illumination Systems II, 594202 (20 August 2005);


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