Design Of Uniform Light Source Based On Diffuse Indirect Illumination

With the continuous advancement and development of society,traditional incandescent lamps,fluorescent lamps and other illumination sources have gradually been eliminated.LEDs have gradually dominated due to their unique advantages and specific optical properties,and are widely used in various environments and fields.LEDs have the advantages of high efficiency,high reliability,long life,and environmental protection.Therefore,LEDs are often used in areas such as image color vision that require uniform lighting conditions.However,LEDs also have some shortcomings.LEDs without secondary optical design are Lambertian distribution,illumination uniformity is relatively poor,and glare is easy to occur,and the illumination efficiency is not high,so it is difficult to meet most lighting system requirements.At present,the secondary optical design is mostly designed based on refraction or specular reflection,which cannot meet the requirements of human visual comfort and general scatter detection illumination uniformity.The main research results of this thesis include:1.A mathematical model of diffuse transmission is proposed and a diffuse transmission free-form surface is designed to improve the illumination uniformity of a specific area of the target plane.First,based on the illumination requirements of the transmission surface and the target plane,a series of nonlinear functions on the diffuse free-form surface contour are established.Then,the equation is solved numerically to obtain a set of point coordinates describing the contour of the surface.A solid model of the light source was obtained using MATLAB data exchange and optical software Trace Pro.Finally,the illumination performance of several lighting systems is compared experimentally.The experimental results demonstrate the effectiveness of the design method.2.In the above design method,it is difficult for the center beam of the illumination system to be completely expanded,which makes it difficult for the illumination system to further improve the illumination uniformity on the target surface.In addition,by applying the above design method to enhance uniformity,the thickness to diameter ratio of the illumination system is generally greater than 1:2,and the compactness of the illumination system needs to be further improved.Aiming at the above shortcomings and limitations,this thesis proposes and designs a combined free-form surface illumination system based on specular reflection and diffuse reflection.First,the specular surface diffuses the center beam of the LED horizontally to the diffuse surface,and the diffuse surface then redistributes all of the light emitted by the LED to the target plane.In addition,when designing diffuse free-form surfaces,the surface shape is constrained by using the same irradiance values ??of adjacent points on the target plane.This thesis proposes a new constraint to solve a series of nonlinear equationsof the surface contour and pass Rotate around the z-axis to obtain a complete free-form surface.3.Lighting uniformity is a very important indicator when evaluating the performance of a lighting system.The assessment of illumination pattern uniformity in previous studies was based primarily on perception under machine vision.However,lighting systems are commonly used for human visual perception,and the visual effects of the human eye must be considered when evaluating the uniformity of illumination.In order to fully consider the effect of human visual perception on the evaluation of illumination pattern uniformity,this thesis proposes a new evaluation index to evaluate the uniformity of illumination patterns by referring to the human visual system(HVS)and according to the bandwidth characteristics of human vision.The experimental results show that the proposed uniformity measurement is consistent with that used by human vision.The evaluation metrics presented herein are equally applicable to the uniformity perceived by the human eye when scaling the size of the spot pattern.This opens up a new field of research for lighting system design and illumination pattern uniformity research.