Research And Analysis Of Lighting System Design Method Based On Free-form Surfac

Freeform surface is an optical surface that is asymmetric,irregular,does not have exact unified mathematical expression and rotational symmetry axis.Its surface shape is completely defined and fitted from discrete data sampling points.Due to its flexible space layout and high design degree,applied them to illumination optical system can not only endow them with more sophisticated beam control capabilities,but also adjust the system structure,improving the performance of illumination optical system.In this paper,LED and laser beam are selected as the system illumination source,and the freeform surface design method of illumination optical system is studied and analyzed,aiming to provide a simple,efficient and wide application illumination optical system design solution,the specific research content is as follows:(1)For LED uniform illumination problem,a reflector was designed based on Light Tools optimization method to generate with uniform illuminance distribution circular lighting spots.Secondly,the design method of freeform reflector and lens based on Snell’s law,edge ray principle and energy conservation law are systematically studied.Simulation results show that the design method is correct and effective.Finally,the near field and far field illumination optical system is designed to study the spot uniformity on the target plane after the extended source passes through the lens and reflector.The results show that the lens based on the point source design has a certain ability to regulate illuminance for the actual extended source,and can achieve illumination spot that meets the requirement of uniformity.But,the illumination spot uniformity of reflector facing extended source is not ideal under the same aperture.(2)For LED collimation problem,a bifocal lens for LED collimation was designed based on Light Tools optimization method,but the optimization method could not meet the design requirements of any divergent angle.Therefore,the freeform TIR lens and reflector design method based on Snell’s law and energy conservation principle was further studied.The design example proves that both of these two illuminance distribution methods can collimate LED source.Finally,different LED chip sizes and target plane distances were set to compare and analyze the parameter characteristics of candela distribution plot,illuminance distribution curve and illuminance distribution map when the source pass through the same caliber TIR lens and reflector.The results show that the divergence half angle of intensity distribution curve has no obvious difference.However,TIR lens has higher light energy utilization rate,maximum luminous intensity and maximum illuminance value,larger spot diameter and better uniformity than reflector.(3)For laser beam shaping problem,an efficient numerical method by iteration in two orthogonal directions is presented for collimated laser beam.Examples of designing freeform surface for laser beam shaping is designed and verified it.Further compared with traditional methods,the results show that the constructed freeform surface by the proposed method is more continuity and smoothness with great fitting accuracy.Moreover,the target plane irradiance uniformity is more stable within the allowable range of machining errors.Secondly,particle swarm optimization is applied to reverse illuminance optimization to solve the problem of decreasing uniformity when the diverging laser beam passing through the initial freeform reflector.The simulation results show that the illuminance uniformity on the target plane can be improved significantly after the divergent laser beam pass through the optimized freeform reflector.