Freeform Optics For High Power LED Packages And Applications

High power light-emitting diodes (LEDs), with increasing luminous efficiency and cost performance in recent years, have more and more applications in general lighting and special lighting, such as LED road lighting, backlighting for LED TV, LED headlamp of automotive, etc.. High optical efficiency, controllable radiation pattern (RP) and high spatial color uniformity (SCU) are three key issues to realize high quality LED lighting. To overcome drawbacks of current optical design methods and to enhance the quality of LED lighting, this dissertation mainly focuses on the research of freeform optics design for LED packages and applications based on these three key issues. Achievements are as follows:In the aspect of optical efficiency and controllable radiation pattern, for the condition of circular-symmetry RP and point source, we propose a new freeform lens algorithm for LED uniform illumination, which makes the calculation simpler for light source with arbitrary light intensity distribution curve (LIDC) and is able to have an accurate control of emitting angles.For the condition of circular-symmetry RP and extended source, we develop a novel freeform lens algorithm based on feedback optimization for extended source problem, including three sub-methods of optimizing the division of target grid, optimizing the division of light source grid and co-optimization design methods. These three methods provide effective ways to overcome the deterioration of RP caused by extended source and enhance the UE significantly from 0.53 to 0.90.For the condition of whole lighting performance of circular-symmetry RP, we develop a new reversing design method for LED uniform illumination, including optimization of LIDC and a new algorithm of freeform lens to generate the required LIDC. According to this design method, two novel LED modules integrated with freeform lenses for direct-lit backlighting are successfully designed to enhance the UE from 0.446 to 0.915 in the situation of large distance-height-ratio, and the quantity of new LED modules dramatically decrease to less than 1/4 quantity of traditional LED modules.For the condition of non-circular-symmetry RP (e.g. rectangular RP) and point source, we propose an improved discontinuous freeform lens algorithm with advantages of arbitrary LIDC available, flexible light energy mapping relationship and shape of RP highly controllable. Moreover, we also develop two new algorithms for continuous freeform lenses, which are the design methods based on the radiate grid and the rectangular grid light energy mapping relationship respectively. Uniform rectangular RPs are able to be achieved by these freeform lenses, which have been applied in LED road lighting successfully.For the condition of non-circular-symmetry RP and extended source, based on the feedback optimization design concept and the integration of secondary optics with the primary optics of LED package, we develop a novel application specific LED package (ASLP) module, which is able to achieve rectangular RP meeting the requirement of road lighting directly. ASLP has advantages of small size (～1/8), high system optical efficiency (enhanced～8.1%), low cost (decline～17%) and easy for customer to use. In addition, a new ASLP module integrated with multi-functions, with advantages of higher system optical efficiency (enhanced～19.4%) and easy to maintain, also has been designed for road lighting.For the condition of whole lighting performance of non-circular-symmetry RP, we propose two new optical design methods for road lighting with high luminance uniformity, which are the combinatorial design method and the freeform lens algorithm for uniform luminance. Both of these two methods are able to enhance the ULof road lighting significantly from 0.30 to 0.70, and have been successfully applied in LED road lighting. Moreover, we also develop a novel asymmetrical freeform lens algorithm to enhance the utilization ratio of road lighting. Average luminance on the road is enhanced 25%by this design method.Except for the aspects of optical efficiency and controllable RP, SCU of LED lighting also has been studied. We propose a novel method to enhance the SCU of LED package by introducing the freeform lens. The SCU of a new LED module integrated with a freeform lens increases from 0.334 to 0.957 significantly. Moreover, the SCU of the new LED module is stable when the parameters of phosphor changing.⊿υ'ν' of LED could be decreased and the illumination quality of RP could be enhanced by the freeform lens designed to achieve high SCU. This method has advantages of simple process, low cost, high optical efficiency and remarkable performance.This dissertation develops a series of novel algorithms for freeform lenses and design methods for good whole lighting performance. Kinds of new freeform lenses and LED modules are designed according to these advanced algorithms. These algorithms and freeform optics provide an effective optical solution for high quality LED lighting with high optical efficiency, controllable RP and high SCU, and could have a widely application in various LED applications.