Exploratory Research On Secondary Light Distribution Of LED Based On Freeform Surface

As human progress continues,energy issues and pollution issues have become increasingly urgent.As a result,while achieving performance,energy conservation and green environmental protection are increasingly valued.In lighting related fields,LED light sources are widely used in various lighting systems due to their small size,high luminous efficiency,and long life span.However,due to the unique light emitting characteristics of LED light sources,secondary light distribution design is required for LEDs.The use of free-form surfaces for secondary light distribution of LEDs is the most efficient method,but the key point of free-form design is that radial and tangential direction vectors cannot be satisfied at the same time.There has been no way to solve this problem.In this paper,non-imaging optical theory will be used to explore the secondary distribution of free-form surfaces.This paper first introduces the basic theory of non-imaging optics in detail,including the application of photometry and colorimetry in lighting engineering,deduces the conservation formula of optical etendue,expounds the meaning of marginal ray theory,and derives the vector of SNELL's law in detail.Among them,the application of optical etendue,edge light principle,and refractive index vector form in optical design is emphasized.In this paper,the non-imaging optical theory is devoted to the research of the free surface lighting design method,and the advantages and disadvantages of the existing design methods are analyzed.The aim is to establish an efficient,accurate and universal free-form surface design theory.Exploratory methods of designing three free surfaces are proposed.They have important reference values for the design of collimating lenses,the design of asymmetrical free surfaces and the design of street lamps.1.Aiming at the traditional collimator,only point light source design methods are considered.The free surface design method based on the brightness distribution of the secondary source is proposed.Effectively improve the TIR lens in the case of extended light energy efficiency and collimation effect.2.For the design of three-dimensional non-rotationally symmetric free-form surface,a method for constructing free-form surface of keel ribs is proposed.Compared with other methods for designing free-form surfaces of the same kind,it has intuitive design,no complicated theoretical calculation,and can satisfy certain requirements.The disadvantage is that for the design with high light distribution requirements,the number of iterations will be many,and the design becomes very tedious.3.Introduced the evaluation indicators of street lighting and related parameters and the basic concept of glare.Taking the road lighting lens as an example,explicitly presented a method for constructing a free-form arc-sagittal free-form surface.Compared to the traditional free-form surface construction method,partially solves the problem of mismatch between tangential and sagittal direction vectors when constructing freeform surfaces.