Micro-holographic light guide plates in LED BLUs

We suggest a micro-holographic light guide plate (mu-HLGP) structure for LED backlight units. A 2-dimesional array of micro-holographic gratings is fabricated on top surface of the light guide plate with a wide range of conical grating directions. Optimization in orientation of the micro-holographic gratings is performed by rigorous coupled-wave analysis, leading to a characteristic function for deriving optimal conical-angle distribution of grating direction. Micro-holographic lithography and UV embossing are used to fabricate the micro-gratings with different conical angles. Hot-spot images and light-propagation line-patterns which were seriously occurred in LED BLUs are successfully eliminated in our mu-HLGP, when a LED is placed at a corner of the light guide plate.