中文摘要：

为了实现光束沿多向准直出射的要求，提出了基于自由曲面的光学器件设计方法。该光学器件是四个侧面为自由曲面、上表面为准直透镜的空心梯形台。基于微分几何理论和折射定律，建立梯形台侧面轮廓曲线上的点所满足的方程，结合Matlab软件数值计算出自由曲面轮廓曲线的离散数据点，将数据点导入Solidworks中进行曲线拟合并建模，进而得到梯形台侧面的实体模型；运用CodeV软件设计出上表面准直透镜。将自由曲面面型数据和准直透镜数据导入到Lighttools软件中进行了仿真模拟，结果表明，该光学器件可实现光线五向准直出射。

英文摘要：

A method for designing optical element , which is mainly based on free-form surfaces, is proposed for realizing multidirectional collimation. The optical element is a hollow trapezoidal platform composing four free-form surfaces in flank and a top collimating lens. According to differential geometry theory and the law of refraction, the equation satis- fying the points on the contour line of the free-form surfaces is deduced, thus some particular discrete points are calculated by combining with the Matlab software. Furthermore, the solid model of the profile of the trapezoidal platform is ob- tained by fitting these data points with the help of Solidwork, and at the same time the lens for collimation is designed thanks to Code V. Finally, simulation is carried out by importing the data of the free-form surfaces and the collimating lens obtained from the two softwares into Lighttools. The result proves that the optical element can produce collimated beams towards five directions.