Design And Applied Research Of The LED Free-form Surface Lens

LED is widely used in the lighting industry as a new type of green lighting source.Regrettably,LED light source can not be directly applied in general lighting systems because of their intensity similar to the Lambertian distribution.Considering this,a secondary optical design is necessary.Where the secondary optics is mostly lens or reflector,and the advantage of using a lens to form a specific spot is better than a reflector,so that the study of LED free-form surface lens becomes very meaningful.The main contributions of the thesis are described as following two points:(1)The relationship of The mapping between free-form surface of circular and annular spot lens and LED light source and target surface is deduced by non-imaging optical theory.Firstly,the free-form surface equations were deduced,and the discrete point coordinates are obtained by solving the equation.Then,the three-dimensional model of circular and annular spot lens was established,and they were respectively simulated by optical simulation.when the light source size is 1mm×1mm,the illumination uniformity of circular and annular spot is 95.7% and 93.7%,and the energy efficiency is 92.3% and 91.1%,respectively.The simulation shows that the illumination uniformity of circular and annular spot is reduced with light source size increasing,but the efficiency keeps unchanged.The illumination uniformity of circular and annular spot is more than 86% and the energy efficiency is more than90% when the light source size is increased to 5mm×5mm.However,the illumination uniformity of circular spot is less than 60% when the light source size is increased to10mm×10mm.This thesis uses the 2D interactive optimization method in the optical analysis software to optimize the circular spot lens,and the optimized illumination uniformity is increased to 85%.Finally,the feasibility of the fixture is verified by simple thermal analysis for the annular spot lens array mode,and the annular spot lens is applied to roading light case by the DIALux software.(2)A free surface solution algorithm for fine mesh density is proposed,and thealgorithm is applied to the free surface of rectangular spot lens.Firstly,the free-form surface solution equation is deduced according to the dividing grid method and the law of refraction and conservation of energy.Then,a rectangular spot lens model is established by solving the free surface discrete point coordinates.The simulation result is well-behaved with good effect of rectangular spot lighting.The illumination uniformity of the rectangular spot is 91.2% and the energy efficiency is 91.1% when the light source size is 1mm×1mm.The simulation shows that the illumination uniformity of rectangular spot is reduced with light source size increasing,but the efficiency keeps unchanged.The uniformity of rectangular spot is 82.3% and the energy efficiency is 91.1% when the light source size is increased to 5mm×5mm.However,the illumination uniformity of rectangular spot is less than 60% when the light source size is increased to 10mm×10mm.this thesis uses the feedback optimization principle to optimize the rectangular spot lens,and the optimized illumination uniformity is increased to 80%.Finally,the rectangular spot lens is applied to roading light case by the DIALux software.