| A lens based on LED is widely used in streetlight,automotive headlamps,projection and medical lighting,which has rectangular spot distribution.However,the LED is a Lambertian light source which is distributed as a cosine distribution.As it is applied to produce a uniform rectangular spot in Lighting Engineering,the structure of lens is non-rotationally symmetric.At present,the LED uniform rectangular spot lens mainly has such problems as complicated surface,difficult design,onerous design process and unsmooth lens surface.In this paper,four kinds of uniform rectangular light spot lens are proposed as radiation type,total internal reflection radiation type,longitude and latitude type and bipolar coordinate system,which are based on the principle of Non-imaging optics and mesh generating method,combined with tangent plane iterative method.The results of comparing all kinds above showed that the light source was unevenly divided in the double-polar coordinate system,the target illuminated plane was trapezoidal partition.The surface of the lens designed by topology was smooth,the spot was rectangular,the spot uniformity reached 85%,and the energy efficiency was 91.32%.When the non-rotation symmetrical lens is processed by the molding technology,the lens is in a closed and high temperature environment,and the temperature and stress of the lens cannot be monitored in real time.In this paper,a finite element simulation model is established for the six stages of heat soak,mold pressing,pressure holding,annealing and cooling for the non-rotational symmetric lens designed above according to the five-element generalized Maxwell Model.The results showed that the maximum equivalent Mises stress of lens is-1.387?m,the strain is small and the residual stress is small.Therefore,LED lens with rectangular light spot for uniform illumination designed by this paper has preferable machinability,non-rotationally symmetric lens is feasible by press molding technology. |
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