Secondary optics is a direct decision to LED street lamp output efficiency, distribution of light distribution, uniformity and glare degree of an important part. Green urban road lighting requirements led street lights just produce a rectangular rectangle around the road, outside the road, such as residential buildings and buildings, such as light pollution as little as possible. XY non-axisymmetric free-form surface secondary optical light distribution design is the best way to achieve this goal. So that in a single lens module can be completed on the high efficiency of the rectangular output spot, the bat wing of the far field angle distribution, and to achieve the light cut design. The structure of the entire lamp cap becomes very simple, as long as these light distribution design of the LED lens module, in accordance with the same direction arranged in a flat PCB board can simplify the LED street lamp mechanical structure, thermal management, and Power supply arrangement. This paper introduces a design of a full reflection type secondary optical lens that achieves high output light efficiency, distribution of bat light distribution, and a more uniform rectangular spot.
LED solid-state semiconductor lighting technology is considered the 21st century strategic energy-saving technology. China, Europe and North America, many countries and cities have been carried out LED road lighting technology development and promotion, compared to metal halide (MH) and high pressure sodium (HPS), LED lights have a longer life (greater than 5 Times); In addition, LED lights also have better controllability and light efficiency, can save as much as 50%. LED lights another green energy is characterized by the light source itself does not contain harmful substances mercury. Optics, LED chip small light source characteristics can be relatively easy to achieve accurate light distribution and secondary optical optimization design, accurate control of the direction of light, the light is fully assigned to the need for lighting on the road to prevent light pollution And glare.
The secondary optical design is an important technique for determining the light distribution curve, output luminous efficiency, evenness, and glare index of LED lights. Most of the high power in the existing market is the distribution of the luminous LED, the spot is round, the peak light intensity half of the beam angle of the full width of about 120 °. If there is no secondary optical light design, then the light spot on the road will be a "round cake", as shown in Figure 1 (a), about 1 and a half of the spot will be scattered outside the road Wasted, and the middle of the spot will be relatively bright, to the surrounding will gradually darken. This light is mounted on the road, the lights will be formed between the obvious light and dark spot distribution, the driver caused visual fatigue, causing the accident. In this case the LED lights can not be called "energy" and "green lighting".
National urban road lighting design standards require LED lights, the spot is rectangular, just can cover the road, and have a good uniformity. LED secondary optical technology, unlike other disciplines, is a non-imaging optics and 3D surface modeling of the cross-disciplinary, secondary optical design can effectively solve the LED lights light efficiency, uniformity, light distribution angle , Glare and safety issues, to meet the requirements of the national standard with the light, the real realization of environmental protection and green lighting. In addition, LED lights have a better color rendering index (CRI), according to the need to adjust the different color temperature so that it can meet the day, night, sunny and rain and other different environments.
The full-reflection secondary optical lens can collect all 180 ° light from the LED chip and reassign it to the specified area, which is a good solution. Free surface of the light distribution can make the LED light intensity of the far field angle distribution was bat wing distribution, so that the spot growth square, and the middle of the spot and the edge of the more uniform, the use of edge light principle, the lens can also achieve the design of light, The The following is a design method of a totally reflective secondary optical lens.