2 September 2008 Further studies on output couplers for edge-lit backlight with emission angle control
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Abstract
We have studied designs of an edge-lit backlight that can switch its emission angle range between a narrow and a wide state. Here, we propose three types of output couplers for this type of backlight unit. These are quadratic prism, triangular prism and arc prism. The probability of extracting the light propagating inside a light-guide does not depend on its propagation angle for each of these output couplers. We conducted ray tracing analysis to compare these output coupler designs. The results show that approximately 65% illumination uniformity and 75% efficiency can be obtained with the quadratic prism. For each setting of the emission range, the width of the angular distribution is switched between 30 and 102 degrees (FWHM). Other two output couplers perform poorly in terms of these optical properties.
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Keita Imai, Ichiro Fujieda, "Further studies on output couplers for edge-lit backlight with emission angle control", Proc. SPIE 7059, Nonimaging Optics and Efficient Illumination Systems V, 70590R (2 September 2008); doi: 10.1117/12.794593; https://doi.org/10.1117/12.794593
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