飞秒激光系统图像调焦装置以及方法

飞秒激光直写技术在复杂三维微结构加工领域具有显著优势，而调焦是否精准直接影响了所加工结构的完整度.提出了在光路中临时置入调焦光源和物的图像调焦技术，通过调节物的位置使其成像面与激光聚焦面一致，从而通过清晰可分辨的成像状态间接反映激光聚焦状态.利用Zemax软件模拟分析了原飞秒激光光路与加入调焦光源和物的调焦光路，二者可实现相同加工物镜后工作距离与良好成像质量，证明了该方法的可行性.通过分析得到该过程的成像误差主要由成像镜头焦深(3.9 μm)引起，我们获得的理想调焦精度可达到1/2焦深以内.设计了单层高度为5 μm的二层圆柱结构，通过多次实验验证了所加工元件高度误差在1.5 μm范围以内，与理论分析一致，满足飞秒激光系统的调焦要求.

An Image Focusing Device and Method for Femtosecond Laser System

Femtosecond laser direct writing technology has significant advantages in the field of complex three dimensional microstructure processing, and the accuracy of the focusing directly affects the integrity of the processed structure.This paper presents an image focusing technique in which light source and object are temporarily placed in the optical path. By adjusting the position of the object, the imaging plane is consistent with the laser focusing plane, so that the laser focusing state can be indirectly reflected by the clear and resolvable imaging state. The Zemax software is used to simulate the processing optical path and the focusing optical path respectively. The results show that the two kinds of simulation results can achieve the same back working distance and good imaging quality, which proves the feasibility of the method. The analysis shows that the imaging error of this process is mainly caused by the focal depth of the imaging lens (3.9 μm), and the ideal focusing accuracy can reach within 1/2 focal depth. A two layer cylindrical structure with a single layer height of 5μm is designed for testing. It is verified through multiple experiments that the height error of the processed components is within the range 1.5 μm, which is consistent with the theoretical analysis and meets the focus requirements of the femtosecond laser system.