Study On Optical System For LED's Automobile Headlamps With Double Freeform Surface

With the continuous improvement of LED technology,LED light source is used in the field of automotive lighting increasingly.Due to the characteristics of the LED light intensity distribution,it is necessary to design secondary optics for LED.And the existing optical system of automobile headlamps exist light energy utilization,spot color temperature stability,uniformity of the spot and the low-beam cut-off line clarity and other issues.So it has practical significance to study the optics system of the LED automobile headlamps with the high light energy utilization and spot temperature stability.According to non-imaging optics theory,the LED headlamp design method with double freeform surface is proposed to meet the national standard requirements.Then develop the optical system for LED's automobile headlamp with double freeform surface.The double freeform surface lenses of the low-beam and high-beam in the headlamp are designed.According to the national standard in the lighting area of the illumination requirements,we can calculate the mapping relationship between the emitted light and the target plane of the chip.The double freeform surface can accurately distribute the light intensity and control the luminous angle,so that the correspondence energy mapping is more accurate.According to the selected light intensity distribution and the national standard in the lighting requirements,we calculate the energy mapping relationship respectively.According to the law of conservation of energy and iterative calculate formula,we can obtain the coordinates of the discrete points on the free surface.The coordinates of the discrete points are imported into 3D software.The lens model is simulated with optical software.The simulation results verify the superiority and correctness of the double free surface.Then the finite element software is used to calculate the temperature field of the system,so that the lamp structure can meet the chip cooling requirements.For further verification,we make the headlamp system.The experimental results are in good agreement with the simulation results,and pass the national standard test,so the design method is superior.Confirming the workability of the double freeform surface lens,it can be widely promoted in the field of automobile headlamp.