针对光线在大角度偏转时菲涅耳损耗大、光强均匀性差等问题，提出了基于最优双偏转能量映射和贝塞尔曲线多参数优化的双自由曲面透镜设计算法，并利用该算法设计了基于板上芯片型（COB）发光二极管（LED）的双自由曲面透镜，该透镜可应用于可见光通信系统的光学发射端。以大面积发光面的COB LED作为光源，通过控制自由曲面透镜内外两个表面上的入射光线偏转角的比例关系（即偏转系数），可降低菲涅耳损耗。构建了出光角分别为180°和260°的大角度均匀光强分布的双自由曲面透镜，其光强均匀度分别为0.92和0.90，其光能利用率分别为89.4%和85.9%。将单自由曲面透镜和双自由曲面透镜的光学性能作对比，结果表明，单自由曲面透镜可实现出光角范围为120°~180°、光强均匀度超过0.85以及光能利用率超过85%的光分布，双自由曲面透镜在达到同样的光强均匀度和光能利用率时，可实现出光角范围为100°~260°之间的均匀光强分布。因此，利用双自由曲面透镜能够实现更大范围出光角的均匀光强分布，从而满足可见光通信系统的光学发射端的光分布要求。

The large angle deflection of light causes such problems as the high Fresnel loss and the poor luminous intensity uniformity. To solve these problems, a design algorithm of double freeform surface lens, which is based on the optimal double deflection energy mapping and the multi-parameter optimized Bézier curve, is proposed. Guided by this algorithm, a double freeform surface lens based on the light emitting diode (LED) of chip on broad (COB) is proposed, and it can be used for the optical transmitting end of visible light communication systems. To reduce the Fresnel loss, we use the large-emission area COB LED as light source, and control the ratio of incident light deflection angles of freeform surface lens’s inner and outer surfaces. Double freeform surface lenses, with large angle uniform luminous intensity distribution and with irritation angles of 180° and 260° respectively, are constructed. The luminous intensity uniformity of the lenses reaches up to 0.92 and 0.90 respectively, and the light utilization efficiency of the lenses reaches up to 89.4% and 85.9% respectively. The optical properties of the single freeform surface lens and the double freeform surface lens are compared. For the single freeform surface lens, light distribution with high luminous intensity uniformity over 0.85 and high light utilization efficiency over 0.85 can be achieved when the irritation angle varies in the range from 120° to 180°. For the double freeform lens with the same luminous intensity uniformity and light utilization efficiency, the irritation angle varies in a broader range from 100° to 260°. This study indicates that the double freeform surface lens can realize uniform light intensity distribution with broad irritation angle, and it can satisfy the light distribution requirements of optical transmitting end in visible light communication systems.