为了实现人工晶状体植入人眼后在远、中、近三个视距范围内均清晰成像，帮助白内障患者获得更好的视觉体验，设计了多焦点菲涅耳透镜，其环带面采用自由曲面的形式。通过每个环带交替控制焦距的方法，避免了随着瞳孔收缩而出现的焦点丢失的问题。基于折射定律的矢量形式，采取迭代计算的方法，设计了自由曲面形式的菲涅耳透镜，并模拟了不同焦点处的能量分布。基于ISO 11979-2标准眼模型模拟了自由曲面菲涅耳三焦点人工晶状体植入眼成像系统，附加光焦度分别为+1.66 D和+3.32 D。通过光线追迹计算了不同光焦度下的调制传递函数；计算结果表明：在空间频率为50 lp/mm时，远焦点、中焦点及近焦点处调制传递函数均在0.2以上，满足患者的使用需求。

In order to help cataract patients obtain a better visual experience with the intraocular lens implantation, which form a clear image on the retina in the far, intermediate and near vision synchronously, we design a trifocal intraocular lens with freeform-Fresnel surface. Each individual focal length is controlled by several different Fresnel zones, which can avoid the focal point disappearing with pupil contraction. Based on the vector form of refraction law, the Fresnel lens with freeform surface is designed by iterative computation, and the energy distribution at different focal points is simulated. Afterwards, we construct the trifocal intraocular lens with freeform-Fresnel surface in the eye model of ISO 11979-2, of which the additional power of the focal length is +1.66 D and +3.32 D, respectively. By ray tracing, the modulation transfer function of the system at different focal point is obtained. It is clear that the modulation transfer function is greater than 0.2 at the spatial frequency of 50 lp/mm for all focal points, which meets the daily vision demand of cataract patients.