等光通量图法中透镜构造的精度应该得到进一步的提高。首先分析了这种透镜构造方法的本质，得到了其与微分方程数值解法中的欧拉法几何意义相同的结论。然后以龙格库塔法为基础，对透镜构造方法做出了改进。在相同的条件下分别用两种方法设计两个发光角为60°的透镜，并在光学设计软件中进行了仿真。光线追迹结果表明，改进后的方法设计的透镜在目标面上形成的照度分布更接近设计预期。该方法实现了对透镜构造精度的提高。

The precision of the lens construction by equi-flux map method should be improved. Firstly, the core of this method is analysed. The result shows that the geometric meaning of this method is the same as the Euler method in numerical method in solving differential equation. Then, based on Runge-Kutta method, the method of lens construction of equi-flux map is improved. Two lenses which have 60° beam angle are designed in the same condition. These two lenses are simulated in the optical design software. The result of ray tracing shows that the illuminance distribution of the lens designed in the improved method is closer to the prescribed distribution. The improvement of the precision of the lens construction is achieved by this method.