LED全反射透镜计算新方法

A New Method for Calculating Total Reflection LED Lens

全反射(TIR)透镜是LED照明中广泛使用的透镜类型。现有的设计方法大多为修正法,即选择一个现有的透镜作为模型,然后根据光学仿真结果对其进行修正。这种方法的使用范围是有限的。也有直接进行形状计算的方法,但计算十分复杂。本文提供了一个不需要复杂计算的TIR透镜的从头计算新方法,即利用制造商给出的LED光强的空间分布和用户的照明要求,直接计算出TIR透镜自由曲面的坐标。此方法的TIR透镜是由透射区(A区)的两个面和全反射区(B区)的三个面两部分组成。光线在本方法中被赋予既有方向属性又有相等能量的属性,称为光通量线。把LED的全部能量平均分配到N条光通量线中,分配方法是用一个数学函数表示厂家给定的LED光强分布,沿此分布曲线分N段积分可求得N条入射光通量线角度序列。另一方面,按照用户给定的照明要求可得到照明光线的光强分布,同样可求得N条出射光通量线角度序列。把这些入射和出射光线各分成A区N1条和B区N2条两部分(N1+N2=N)。由上述两个序列,分别在A、B两个区按照折射定律计算,得到透镜五个面共5N个折射(反射)点的位置,当N足够大时可得到平滑的透镜。这种计算方法可以选择不同的计算参量,从而得到不同的TIR透镜形状,如准直透镜、不同照明角度的透镜、非均匀照明的透镜等,适合用在范围很广的多种照明场合。计算过程没有复杂的数学运算,而计算结果准确,物理意义明确,几乎不需要模拟修正就可以直接用来建模加工。此方法有较高的可靠性和灵活性。

Total reflection(TIR)lenses are a widely used lens type in LED lighting.However,most of the existing design methods are modified methods,that is,selecting an existing lens as a model,and then modifying it according to the optical simulation results.The use scope of this methods is limited.Although there are methods of directly performing shape calculations,but the calculations are very complicated.A new ab initio calculation method for TIR lens without complex calculation is presented in this paper.That is to directly calculate the coordinate of the free-form surface of the TIR lens,by using the spatial distribution of LED light intensity given by the manufacturers and the user’s lighting requirements.The TIR lens of this method is composed of a transmission region(zone A)with two surfaces and a total reflection region(zone B)with three surfaces.In this method,light is endowed with both directional property and equal energy property,which is called light flux ray(LFR).All the energy of the LED is equally distributed to N LFRs.The distribution method is to use a mathematical function to represent the intensity distribution of the LED given by the manufacturer.The angle sequence of N incident LFRs can be obtained by integrating N segments along the distribution curve.According to the lighting requirements given by the user,the lighting intensity distribution can be calculated,and the angular sequence of the N outgoing rays is also obtained.The incident and outgoing rays are divided into two parts,N1 for zone A and N2 for zone B(N1+N2=N).According to the law of refraction,the positions of total 5N refraction(reflection)points on five surfaces of the TIR lens are calculated in A and B regions respectively using above two sequences.When N is large enough,a smooth lens can be obtained.The different calculation parameters can be selected in this method to obtain different TIR lens,such as collimating lenses,lenses with different illumination angles,lenses with non-uniform illumination,and the like.Suitable for a wide range of lighting applications.There is no complicated mathematical operation in the calculation process.The calculation result is accurate and have clear physical meaning,and it can be directly used for modeling processing with almost no simulation correction.This method has proved to be highly reliable and flexible.