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DESIGN OF LENS WITH RECTANGULAR LIGHT SPOT FOR LED UNIFORM ILLUMINATION

(National Engineering Research Center for Hight Efficiency Grinding,Hunan University,20 Changsha,Hunan,China)

Abstract: In order to improve energy efficiency, light distribution uniformity and lens surface smoothness of LED rectangular spot lens, a lens was designed, which with uniform illumination and a rectangular light distribution.The solid angle of light source is sampled in a double-polar coordinate system,and the target rectangular illumination surface is divided into a trapezoidal region corresponding 25 to the solidangle of light source by the energy conservation principle. The lens model is obtained by Snell's theorem and tangent plane iteration method. The simulation results show that 91.32% energy is concentrated in the rectangular spot of 800mm×600mm for the LED spot light with the light emitting angle of 120 degrees, where the normalized illumination uniformity is 85% and the relative standard deviation is 0.416%. The lens surface is smooth and the curvature changes gently. Therefore, in the 30 double-polar coordinate system, light source is split in a non-uniform grid and the target illumination surface is divided into a trapezoidal target illuminating surface block corresponding to the solid angle of light source, which is favorable to improve energy utilization ratio, light distribution uniformity and lens surface smoothness of LED rectangular spot lens.
Key words: optical; non-imaging optics; light-emitting diodes; rectangular light spot

Figure.1 α-β meshing method (a) diagram for the modified double-pole coordinate system; (b) diagram for the solid angle of light source Fig.2 Non-uniform sampled grids in first quadrant of the modified double-pole coordinate system and related mapping mechanism between source and target (a) light source solid angle grid; (b) target illumination grid

Figure.3 Lens structure diagram

Figure.4 Lens simulation effect (a) normalized Illumination chart; (b) normalized light distribution uniformity

Figure.5 Analysis of lens with different luminous angle

Figure.6 Analysis of lens performance with different aspect ratio of light