High Uniformity Illumination Design For COB Based On Normalized Feedback Iteration Of Illuminance Grid

At present,the light source of LED lighting mainly has a single light source and chip on board package COB(Chip On Board)light source in two forms,compared to a single light source,COB light source with low thermal resistance,surface light,small size,design flexibility and other advantages,in the stage lighting,backdrop lighting,street lights and other fields have a wide range of applications.And the uniformity of the lighting area has high requirements for variety applications in the above areas.In this paper,based on the theoretical basis of non-imaging optics and free-form surface,an exploratory study is conducted for the optical design of LED point light source and COB surface light source by analyzing the optical luminescence characteristics of COB light source,and finally an iterative method based on the normalized feedback of illumination network is implemented to design a free-form surface with COB as light source and different shapes of high uniformity of secondary light distribution.The main framework of the paper is as follows:First,the luminescence characteristics of LED point light sources as well as COB light sources are described,with emphasis on COB light sources,to provide initial design input for the subsequent secondary light distribution design.Through the study of non-imaging optical theory,the light tracing relationship between the light source and the target surface is established based on the energy grid mapping method.For the point light source design to achieve circular spot lighting free-form lens,after the simulation of the illumination range of the target surface illumination uniformity of 91.36%,the system output light efficiency of 95.3%(the paper involves the light efficiency unless otherwise specified,are set to disregard Fresnel loss and total reflection loss).Designed to achieve rectangular spot lighting freeform lens,after simulation in the illumination range of the target receiving surface illumination uniformity of 91.61%,the system output light efficiency of 96.5%,to provide the initial model structure for the optimization of the design of COB light source secondary light distribution free-form surface.Then,the free-form surface obtained from the point light source is used as the initial model structure for the secondary light distribution design of the COB surface light source.The optimization algorithm based on the normalized feedback of the illuminance grid is used to optimize the rectangular spot of the COB surface light source,and the illuminance uniformity of the rectangular spot of the target surface reaches 92.86%after simulation.The high uniformity of rectangular spot illumination for COB surface light source is achieved.The optimization algorithm based on the normalized feedback of the illuminance grid is applied to the feedback optimization of the circular spot of COB surface light source,and the illuminance uniformity of the rectangular spot of the target surface reaches 96.14%after the optical simulation,which shows that the method can be applied to the secondary lighting design of COB light source with different illumination shape requirements with high uniformity.Finally,according to the design results,a free-form lens was machined and a test platform was built to test the illuminance distribution of the designed 10 mm diameter COB surface light source with a rectangular spot free-form lens.The collected illuminance data are analyzed by various algorithms for light field modeling.The test results are consistent with the design simulation in the overall light intensity shape,illuminance uniformity and other experimental test results and the overall trend of the simulation results,verifying the correctness and feasibility of the design method.