21 April 2006 Design of a light-guide used for the real-time monitoring of LCD-displays
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Abstract
We describe the design of a light-guide that is part of a sensor which continuously measures the "quality" of Cold Cathode Fluorescent Lamp (CCFL) backlights. This sensor gives information to the electronic system that compensates the screens degradations. The light-guide should fulfill several conditions. First of all the acceptance angle of the light-guide should be in accordance with a predefined value, this for reasons of calibration. Secondly the energy-loss inside the light-guide should be minimal. This is indispensable especially when using the light-guide for color screens. In this case the flux density on the photodiodes surface is much lower in comparison with monochromatic screens due to the color filters which are present. Finally we want the light-guide to be low-cost and we have to make sure that the design could easily be built inside a screen. For the optical design of this light-guide we used both sequential and non-sequential ray-tracing software. We started our simulations with an L-shaped light-guide profile. The dimensions of this guide were chosen in such a way that the element easily fits into a standard screen. To make sure that the sensor only captures light within the desired acceptance angle we proposed a system using a lens on top of this light-guide. In this paper we describe the design and simulation results of this L-shaped light-guide with extra lens. After making some final changes to the design to reduce the influence of environmental stray light, we ended up with a light-guide which fulfilled most of the predefined specifications.
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W. Meulebroeck, W. Meulebroeck, Y. Meuret, Y. Meuret, C. Ruwisch, C. Ruwisch, T. Kimpe, T. Kimpe, P. Vandenberghe, P. Vandenberghe, H. Thienpont, H. Thienpont, "Design of a light-guide used for the real-time monitoring of LCD-displays", Proc. SPIE 6196, Photonics in Multimedia, 61960M (21 April 2006); doi: 10.1117/12.660885; https://doi.org/10.1117/12.660885
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