Design Of Free Surface Optical System For LED Secondary Light Distribution

Nowadays, the application of solid state lighting rather than the coventional lighting, which are mainly consist of incandescents, halogen lamps and so forth, is concerned by more and more countries. The research about LED, the new generation light source in solid state lighting, has been a rising star of optical field. LED has a lot of advantages such as small size, high brightness, low power consumption, low cost, long operating life and environment friendly, and this can be widely used in various areas. However, how to achieve the design of efficient LED light configuration to fulfill most of illumination demonds is a problem that should be solved urgently now. Based on freeform surfaces, LED second optical elements have a high degree of freedom, and can adjust the light distribution emitting from the LED effectively. Moreover, the construction of freeform lighting systems is more simple than traditional methods of light configuration relatively, so they can easily achieve more complex lighting requirements, and have the great research value. Therefore, this paper will discuss how to design the freeform illumination systems for LEDs in terms of two typical cases in lighting field——collimating illumination and uniform illumination, the research process are as follows:The design method of the initial freeform surface was researched. Firstly based on the laws of geometrical optics, the calculations of discrete points on freeform surface are derived. And then according to the law of conservation of energy, the energy mapping grid pattern between the LED and target illumination plane is constructed. Next, the grid patterns of rotational symmetric optics system and non-rotational symmetric optics system are solved by energy mapping method respectively. Besides, two examples about designing freeform optics system will verify the accuracy and reliability of this design method.By citing the LED searchlight optical design and LED streetlight optical design for instance, the design process of the collimating illumination optics system and the uniform illumination optics system are discussed. And a kind of novel collimating system which is consist of a refractive freeform lens and a freeform reflector, plus a freeform lens which can achieve an uniform rectangular light distribution are designed respectively. Besides, two different optimization methods are used to optimize those two designed systems. Finally the performances of two systems are both excellent.