Secondary Optical Design Of The LED Road Lighting System

LED as a new type of solid-state light sources of cold, possessing thecharacteristics of small volume, long operating life, high luminous efficiency,energy saving and environmental protection. The broad market prospect hastriggered the climax of study, especially in the realm of road lighting, but the raythat emits from LED chip takes on the form of Lambertian distribution, if thiskind of light distribution is not modified by optical design process and put intopractical use directly will cause serious light waste. And problem of secondaryoptical design of LED has become the main factor that hinders the furtherpopularization of LED.At present, practical testing method has been commonly used aiming tosolve the problem of secondary optical design of LED road lighting system, thatis to say, establish the initial model of the lens in computer by means of relevantsoftware, and produce the real structure according to this model, then practicaltesting will be done, next, changing the structure of lens according to the testingresult. The efficiency of the method is very low, and the result needs to bechanged frequently, so the developing cycle is often prolonged, this increases theconsumption of manpower and material resources. In this paper, a new methodhas been adopted aiming to solve the problem of secondary optical design ofLED and raise the design efficiency, this new method combines the Non-imagingoptics theory with lighting designing software and computer programming.Deducing the formula of the lens in according with etendue conservation inNon-imaging optics theory, acquire the discrete points on the freeform lens byMatlab, and doing simulation work in Tracepro to validate its correctness.Two freeform lens that realize round uniform illumination and rectangleuniform illumination respectively have been produced. This method changes theoriginal idea, computer programming makes the complex process easy and raisesthe designing efficiency. Moreover, freeform as the core concept of designing process, how to designthe appropriate surface to meet the requirement of the road lighting is the keypart during the designing process. Relevant research has been made. Thedesigning method of freeform lens could be divided into two kinds: one is forsingle source; main method of this idea is Tailoring of H.Ries. The other is forextended source, main method this method is SMS(simultaneous multiplesurface) of P.Benitez. But these two methods are too complex to understand andthe final problem has to be converted to second order Monte-amp equation. Sothey are not suitable for practical designing. In this paper, novel gird-mappingmethod has been adopted in calculating the surface data, this method dividing thesource and target plane and establish the relationship between them, this methodsimplifies the deducing process and arithmetic operation, and could be easilyrealized by programming and it improves the design efficiency compared withthe traditional design approach.According to the scheme proposed in this paper, three dimensional modelhas been established, and simulation work has been made about theirperformance: the illumination uniformity of the round uniform lighting andrectangle uniform lighting has reached85.1%and75.2%respectively,meanwhile, bats airfoil light distribution curve that is required by the regulationof road lighting has been realized by the rectangle uniform lighting.