Research On Indirect Illumination Method Based On LED Array Spacing Optimization And Diffuse Freeform Surface

LED is the light source which has great potential and competitiveness in the twenty-first century,and compared with traditional light sources,it has the advantages of high efficiency,energy saving and environmental protection,good durability,long service life and convenient control,it has been widely used in indoor and outdoor lighting,projection,backlight,car lamp etc.However,due to the fact that the LED light is in Lambertian distribution,it is usually necessary to carry out secondary optical design on it,otherwise the illumination uniformity and efficiency requirements at the illumination area could not be satisfied.Therefore,this paper proposes a design method of indirect illumination based on diffuse reflection freeform surface,studies have been carried out on methods of optimizing design on LED array spacing,diffuse freeform surface and its feedback of indirect illumination,so as to realize high uniformity of illumination,and explore the improving degree of light use efficiency.Firstly,the method of optimizing the LED array spacing in the indirect illumination system of diffuse freeform surface is studied in this paper.According to the characteristics of LED light distribution and high diffuse reflection surface,the freeform surface and target surface illumination function equations of LED spacing parameters are deduced.The optimal evaluation function of LED array spacing is established,and the optimal spacing is obtained by programming.The uniformity of target surface of the three arrays when adopting different distances are tested and simulated,and the experimental results show that:(1)The uniformity of the target surface under the three kinds of arrays is more than 90% when the spacing is optimal.(2)When the three arrays are in the optimal spacing,diffuse freeform surface under the target surface illumination uniformity is higher than those in diffuse reflection hemisphere lighting and direct lighting of the same condition.Then,in order to realize uniform illumination of target surface and improve the efficiency of system,a method of designing diffuse freeform surface in indirect illumination system is proposed.Firstly,in the spherical coordinate system,the optical model is established,the diffuse reflection surface and the surface differential equation group are deduced,and the energy conservation equation is given.Then,the freeform surface data is obtained by solving equations numerically.Finally,the data is imported into simulation software,and the near-field and far-field distance illumination simulation are compared.The simulation results show that the diffuse freeform surface illumination is better than the direct illumination and the diffuse reflectance hemisphere illumination in terms of the uniformity and efficiency of the target surface,both in the near field and far field illumination.Finally,this paper proposes a method for optimizing the design of diffuse freeform surface feedback in indirect lighting system,and explores the feasibility of the method in improving the illumination uniformity and efficiency of the target illumination area.According to the initial surface simulation illumination results and the feedback function of expected illumination to correct the default illumination distribution,get a feedback of the new surface.Import data of the new surface into the software to carry out simulation,it could be found after comparing simulation results before and after the feedback that,the illumination uniformity of the target surface was increased from 73.7% to 81.7%,and the efficiency was increased from 4.3% to 10.5%.The simulation results show that the feedback optimization method is feasible and effective.