Research On Optical Design Of High-Power White LED Automobile Headlamp

Along with the advance of automotive lighting technology, white LED has been widely applied in automobile headlamps system, by its advantages of long life, small volume, high luminous efficiency, energy saving, environmental protection, and replace the other light. Due to the luminescence characteristics of the LED light source which is solid cold light source are different from traditional automotive headlamp light, we need redesign the secondary optical system design in order to satisfy the requirement of the national standard. Therefore, research automobile headlamp system based on high-power white LED sources has very important significance.In this thesis, a different design method of automotive passing low-beam and high-beam system was proposed based on the standard of freeform surface design and the requirements of national standard. In the one hand, a new LED headlamp low-beam system, which was designed by variable corss-section ellipsoid reflector, flap and free-form surface lens, could realize low-beam light distribution in variable corss-section ellipsoid reflector and rational distribution of LED energy by using the baffle to form clear light and dark cut-off line and the free-form surface lens to control light. In the other hand, the design of a new LED headlamp high-beam system, which was composed of the combination of total reflection lens and free-form surface array, was made up of four LED component systems with same structure. The LED component system arrayed in diamond, and the LED light was aligned through the total reflection lens, meanwhile the aligned light was distributed to particular region by the free-form surface array. According to the theory of non-imaging optics and the energy conservation law, the correspondence between the angle of the light reflected by the variable corss-section ellipsoid reflector or total reflection lens and the coordinates of point in the target plane was established. Furthermore, by using Solid Works mechanical modeling software, the surface entity was fitted by free-form surface point coordinates which calculated base on the reflection law and the refraction law, and finally the model of free-form surface lens and the free-form surface array was built.Then the whole system was imported to the Tracepro software for simulation by using Monte Carlo method. The simulation results showed that the low-beam and high-beam system has formed a default type of light distribution on the 25 m light screen. The various test points and areas of the illumination distribution completely satisfied the requirements of GB25991-2010 in high system efficiency, which the low-beam energy utilization rate was 80.54% and the high-beam energy utilization rate was 90.57%. All of these evidences verified the correctness of the design scheme.