A Non-imaging Optical Design Method For Free-form Lens Base On Wave-front Reconstruction

According to the development of LED, a technical summary of the secondary optical design for LED illuminations is presented. And a novel free-form lens design method, which is based on inverse wave-front reconstruction, is proposed in the present dissertation.In this method, the first wave-front is come from light source, while the second wave-front is reconstructed of target light distribution by using the Fresnel-Huygens principle, then the two optical free-form surfaces can be calculated with the transmission functions of light wave and some special skills. For simplicity, the input lights are confined to the parallel lights, so the first wave-front is of a plane, and the first optical surface is also assumed as a plate surface.The optical simulation results show that the luminous efficacy of the lens designed by this method comes to 0.81, and the light distribution can meet the requirements. The main works in this dissertation are listed as following:1. According to the geometric relations between the light and the wave-front, a new method is put forward. First of all, the target surface illumination would be turned into a wave-front, and then do the same to the light source surface. After that those two wave-fronts were designed at the same time by the optical path difference. At last, evolution lens between the two wave-fronts was designed, so as to achieve the design requirement.2. The goal of this article is to design a distribution lens to meet any light distribution of the target surface. With the method of the wave-front reconstruction, a LED light distribution lens with high utilization rate of energy was designed and the lens can be easily processed. This method will be used to promote the popularity and development of non-imaging optics design and provide some theoretical and practical basis for the future research. In the process of writing this paper, we mainly did some research with the design method of wave-front reconstruction were done and build software model by this method. At last, we got the simulation and analysis the results.3. The lens was designed with setting the logo of ZJUT as its target surface in this article. The light source is straight rectangular LD. With the method of wave-front reconstruction, one of the lens’s surfaces is flat and the other one is free stuff. The simulation result shows that a clear target surface light distribution was gotten and the efficiency of light reached more than 0.8.4. Only the single level gray on the target surface lens was designed so far, we can design the multi-level gray light distribution on the target surface in the future. What’s more, the lens for the point light source and other shape light sources will be designed. This is the direction of the further research about the algorithm of wave-front reconstruction.