Research On Homogenization System Of Ultraviolet LED Based On Free-form Surface

Ultraviolet LED has many advantages like energy saving,eco-friendly,high energy efficiency and so on.It has been widely used in the field of ultraviolet special lighting.Most optical systems of ultraviolet illuminance,such as ultraviolet ink curing and ultraviolet exposure machine,need uniform illumination,but the intensity of LED is Lambertian distribution and cannot be used for uniform illumination directly.Therefore,the ultraviolet LED illumination shall be uniformly designed.The common methods of light uniform conclude fly eye lens illumination,square rod illumination,placing compensation filter,mirror method,etc,and they all have their own strengths,weaknesses and their applications.With the development of free-form surface machining technology,the free-form surface lens is gradually used in the LED optical system for uniform.The design of free-form surface is flexible and has high degree of freedom.Using free-form surface can greatly simplify the structure of the illumination system,accurately control the beam distribution,and effectively achieve the desired uniform illumination.In this thesis,two cases of light uniform are researched according to the actual industrial requirements:the ink curing system and the light exposure machine system,separately designed free-form surface lens for light homogenization.In the ink curing system,the data of free-form surface is obtained by numerical solution partial differential equations combined with feedback optimization.And the specific process is:using the vector form of the refraction law to establish the partial differential equations of the free-form surface,and then establish the correspondence relationship between the free-form surface and the target surface by the law of conservation of energy,thereby simplifying the free-form surface partial differential equations,and then calculating the discrete point information of the free-form surface by programming and the surface is modeled in software.Finally,the surface data is optimized by the method of feedback optimization.After the design is completed,multiple LEDs with different wavelengths and free-form surface lens are combined together and arrayed on the arc surface as the final curing light source system.The simulation verified that a single lamp bead can achieve high uniformity;and light source array can also get a light spot fulfil the requirement of the illuminance intensity,uniformity and the wavelength uniformity.Then,in the parallel light exposure system,the design goal is established through changing the evenly distributed of target illumination into emergent light energy distribution,using the refraction law of vector form and geometric relationship to establish the free-form surface equation,solving the equation numerically to obtain discrete point data and the surface is modeled in software as well.The simulation result of ray tracing shows that using the free-form surface lens can effectively improve the illumination uniformity of the target surface illumination spot.