针对动车组空间三维坐标的测量需求,设计了三维激光雷达共光路变焦光学系统。系统采用发射/接收共光路的结构形式,以高斯光学为理论基础,对能量传输进行了详细的分析, 得到扩束透镜链的严格限制关系。为简化系统结构, 利用液体透镜代替传统的机械变焦机构, 以几何光学为理论基础, 计算出光学系统初始结构, 并采用Zemax光学设计软件进行仿真, 设计出三维激光雷达发射/接收共光路光学系统。该结构形式不仅提高了系统同轴度、减小外部干扰, 还简化了结构、缩小了仪器体积。采用液体透镜调焦代替机械调焦, 避免了调焦引起的机械振动, 有效提高了激光雷达的定位精度。通过改变液体透镜的光焦度, 实现了在2~30 m测量范围内, 发射光学系统在被测物体表面的光斑半径小于20 μm/m, 接收光学系统超过90%的聚焦能量集中在半径小于1.6 μm的圆内, 满足用户要求。

In order to meet the need of measuring the train groups’ three-dimensional coordinates, a 3D laser radar common path zoom optical system was designed. According to the characteristics of laser beam expender, multistage laser amplifiers were carried out by using lens chain. Based on Gauss optics and geometrical optics, the optical structure of the laser emission system based on liquid lens was fully analyzed, and the key parameters of the initial structure of optical system were calculated. Using Zemax optical design software to optimize the simulation, the 3D laser radar transmitting/receiving optical system was designed. The spot diagrams of the transmitting optical system which used a liquid lens to zoom were all less than 20 μm/m within the image distance range between 2 m and 30 m, and the spot diagram decreased with the increase of the distance. By minimizing the spot size which was detected by the array detector channel of the receiving system to focus the energy in one point, then the power of liquid lens was the optimal state to make sure the spot diagram in the target was smallest. By optimizing the design, the radius of the 90% energy concentrated area were less than 1.6 μm. The optical structure not only improves the system alignment, reducing the external disturbing, but also simplifies the structure of the instrument volume. Using the liquid lens focusing instead of mechanical focusing to avoid the vibration, and the positioning of the laser radar was proved.