| Various advantages can be expected when using Light Emitting Diode (LED) as the light source to build up the illumination system: saving energry, lower pollution, miniature, and longer lifetime. But the layout and the luminance distribution of the LED are so different from the traditional sources that the conventional illumination systems are not suitable for LED, so a special optical design should be done according to the illumination requirement. Therefore, the research on the optical design method for LED lighting system not only has theoretical value but also actual meaning. According to the common lighting requirements, this subject researches on the arrangement of LED and uses the edged-ray theory and grid method to design an optical free-form surface to get a highly efficient optical system with uniform distribution.Firstly, LED array arrangement problem: on the premise of having known the radiation characteristics of LED source and the required illumination distribution on the target surface, we establish mathematical models of the sources, then calculate the extreme value of the interval size of the LED array to achieve a uniform illumination surface based on differential geometry. A variety of optical arrangement models are designed according to the actual lighting requirement to make the lighting surface uniform.Secondly, free-form surface problem: on the premise of having known the radiation characteristics of LED source and the required illumination distribution on the target surface, the point data of the free-form surface can be achieved based on the edged-ray theory and grid method. According to the lighting requirements, the optical systems are designed. With the LED source emerged in the optical system, an ideal efficiency of 100% can be achieved.Using the design theory mentioned above, several practical optical systems are designed and simulated. According to the simulation results, the optical systems are proved to be right and effective.
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