Abstract
We analyze the polarization-preserving property of two conventional
edge-lit light guide plates (LGPs) based on scattering dots and refractive
microgrooves and find that these two structures almost completely depolarize
the incident linearly polarized light. We then propose a new edge-lit LGP
based on total internal reflection (TIR). Simulation results show that such
a TIR-based LGP can largely preserve the polarization state of the incident
linearly polarized light. The polarization efficiency is 77.2%. By incorporating
a linearly polarized LED to our proposed LGP, the overall optical gain is
1.54 compared with the backlight system with an unpolarized LED. At on-axis,
the luminance is
$2.4\times$
higher. Because the output light is concentrated near the surface
normal direction, no additional brightness enhancement film is needed. This
polarization-preserving LGP enables a polarized or partially polarized LED
backlight to be used, which in turn greatly enhances the optical efficiency
of a LCD.
© 2013 IEEE
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