Design Of Free-form Surface And Feedback Optimization Method Based On Diffuse Reflection Indirect Illumination

Light emitting diode(LED) compared with the traditional light source, has many advantages of energy saving, environmental protection, long life and small size. Due to the characteristics of the light field distribution of LED light source, it is necessary to carry out the second optical design to meet the requirements of the actual lighting appropriately. Therefore, we firstly design the diffuse reflectance of free-form surface and combine with LED light source arrays to construct the diffuse lighting system, in order to improve the uniformity of illumination on the target plane and to improve the utilization rate of lighting energy. Then we puts forward the feedback method to optimize the concept of initial surface type, after the first feedback optimization, the initial diffuse reflecting hemisphere forming a new facial contour. Not only the uniformity on the target surface was increased from 75% to 80%, but also the system energy utilization rate was improved.In order to realize the secondary optical design of LED light source, this paper make the high irradiance uniformity degree and light use rate as goals, a variety of LED arrays and high diffuse reflection free surface of indirect illumination method was composed both in the near field and far field of the two lighting conditions, respectively. Firstly, the Lambertian characteristic of LED point light source was taken into account, the lights based on the radiation distribution of the inner surface of the model fired diffuse reflection free-form surface, then combined with diffuse reflectance free-form surface bidirectional scattering distribution function, the secondary reflection lights finally cast into the preset target surface; Secondly, the uniformity on the target plane could be calculated by the law of conservation of energy. Therefore, we can construct a diffuse indirect lighting system consists of LED light source arrays, diffuse reflection surface and the target surface, then the illuminance values Et can be obtained easily. Finally, through the numerical methods for solving the free surface of the planar data, we may conduct a large scale simulation tests at the target surface by using the optical software TracePro. Experimental results show that: compared to traditional direct lighting and diffuse hemisphere as indirect lighting method of planar, our design has a better uniformity of illumination and higher light utilization rate.While the initial design model can not meet the lighting requirements of the situation, the feedback optimization method was proposed. According to the difference between the actual illumination and the desired illumination, we can feedback the value to the design process, then the new planar results of the initial diffuse reflecting hemisphere after a feedback optimization can be concluded. In order to make sure the feasibility analysis of feedback optimization method in the design of the free surface. Considering the complexity of the problem, this paper chooses hemisphere as the initial facial and selects the circular spot for specific research. In circular spot case, the illumination uniformity of the target surface is increased from 75.7% to 80.8%, and the light energy utilization rate of the system is also increased from 12.6% to 15.7%. The results show that: this method can improve the uniformity of illumination on the target plane and has certain innovation in a certain extent.