Research And Design Of Secondary Optics Based On LED Uniform Illumination And Diffuse Free-form Surface

As a new generation of light source,light-emitting diode(LED)has the advantages of high efficiency,energy saving,environmental protection and long service life.It is widely used in the series of digital illusory color,square lighting,courtyard lighting and projection lighting.As the spatial light intensity of LED light source is similar to the Lambert cosine distribution,the direct use of LED lighting will form a circular spot which will gradually darken around the center light on the target surface,which would result in poor irradiation uniformity,low energy utilization and producing glare.It is obvious that the direct use of LED lighting is difficult to meet the actual lighting needs.Thereby,in order to make the light energy distribution meet the actual lighting needs,it is supposed to carry out the secondary optical design to achieve the purposes of high irradiation uniformity and high lighting efficiency.This paper adopts an indirect lighting mode that combines TIR(total internal reflection)and diffuse free-form surface.The design which uses diffuse free-form surface to achieve the irradiance optimization is proposed to make the irradiance of light reach the target lighting surface.Under the condition of ensuring the irradiance uniformity,the lighting efficiency will be improved.The main research results of this paper:1: An indirect lighting mode that combines the using of LED and diffuse transmission free-form surface is proposed,and a compact rotationally symmetric lens with two free-form surfaces is designed based on the edge light principle.Firstly,regarding the LED light source as a point light source,the mathematical model is built according to Snell’s law,partial differential equation method,energy conservation law and refraction law.Then,a series of related numerical equations are established,and a series of two-dimensional contour coordinates in all directions are obtained by Matlab,and a free-form surface len is synthesized by Solid Works.The simulation result shows that this method has better uniformity and higher efficiency than the single diffuse transmission free-form surface and plane.2: Although it is an effective way to improve the illumination performance through redistributing the emitted light by reflection or refraction,the traditional mirrors or refractors require high machining accuracy and materials.In this paper,a kind of illumination system based on diffuse transmission surface for oral surgery illumination is proposed,which improves the uniformity of illumination in a specific area of the target plane.The system provides a uniform and wide field of vision for the illumination in oral surgery.Firstly,according to the light-emitting characteristics of a single LED Lambert body,the mathematical model of diffuse transmission free-form surface irradiance distribution is built,and the expected value of the target lighting surface is set.Then the nonlinear equations of light distribution on the outer surface could be derived,and a set of two-dimensional curves are obtained by solving the equations.Finally,the corresponding free-form surface would be gotten by rotating the resulting curves imported into the 3D Modeling Software Solidworks.The simulation result shows that the optical uniformity of the double free-form surface can reach better.3: Based on the above lens design,we know the diffuse surface is obtained by two boundary lofting.Hence,if the diffuse free-form surface has not been specifically designed,the effect of the obtained lighting system often would not meet the actual needs.To solve the above problems,according to the Lambert characteristics of LED and the ideal diffuse reflective surface,this paper proposes a design of multiple diffuse reflective free-form surface and establishes the corresponding mathematical model based on a single Lambert led.Then the Runge Kutta method is used to solve the coordinate data of two-dimensional curve,and the two-dimensional curve is used to get the diffuse free-form surface.At last,the software Trace Pro is used to simulate.The simulation result shows that the uniformity and efficiency are improved obviously.