Abstract
The significance of an ultra-thin unit (BLU) for a current liquid crystal display (LCD) is increasing. Freeform lenses are commonly used in a direct-lit BLUs to reduce the thickness and increase distance�height ratio (DHR). However, it is difficult for the existing refractive lenses to achieve larger DHR under smaller optical distance (OD). To solve this issue, a new hybrid lens containing multiple refraction surfaces and total reflection surfaces is designed in this paper for ultra-thin backlight. Combined with a micron-scale surface microstructure, it can achieve satisfactory uniformity with small OD and large pitch distanced. The simulation results shows that the emergent light spot is uniform under the illumination of extend light source when OD=3mm. The spot diameter can reach 20mm with DHR = 6.67. It proves that the designed lens with hybrid structures for ultra-thin backlight units in this paper has the advantages of small size, large DHR, high uniformity and great practical application value.
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