用照度分割法设计路灯花生米透镜，具体思路参照 张奇辉大功率LED照明系统光学设计方法研究 第四章　（非原创）(The method of illumination segmentation is used to design the peanut lens of street lamp. The concrete idea is referred to the fourth chapter of the optical design method of Zhang Qihui high power LED lighting system (not original))