Optical Design For Uniform Illumination Arrayed Led And Gradient Index Lens

For direct type LED panel lights, the uniform irradiance distribution analyses on the rectangular array LED and the honeycomb array LED are investigated in the present thesis. An irradiance profile is constructed by using the irradiance distribution symmetry to design a free-form surface lens, which can yield a uniform lighting.For the panel light with a rectangular LED array, a segmented irradiance curve of a unit source is presented. Each LED unit is composed of an LED element and a rotational free-form lens. A direct panel light with square LED array is given as a goal, whose distance-height ratio is about 4.1. Then the freeform lenses are built after some optimizations, and the optical simulation results show that the uniformity on the target screen is greater than 0.85, and the optical effect is higher than 0.9. This method can be applied to the extended light sources. The limit of irradiance uniformity of the direct LED panel lights mentioned above can be achieved by using the symmetrical analysis method which is useful for the optical design of LED panel lights.The optical design method for rectangular array LED panel lights can be extended to the honeycomb array LED backlights. The irradiance curve on the target surface is a segmented cosine curve. Its uniformity is higher than that of the segmented straight line case(0.82). Optical simulation result shows that the luminous efficiency is about 0.92 and the uniformity is more than 0.92.The history and current situation of the gradient index(GRIN) optics are introduced in this thesis. Based on the ray tracing equation, the traces of lights are simulated with a MatLab program. All the lights are emitted from a point source, passed through GRIN lens and hit on the target surface. The ray tracing method is verified by the simulation result from FEMLab software.