飞秒激光系统图像调焦装置以及方法

Femtosecond laser direct writing technology has significant advantages in the field of complex three-dimensional microstructure processing, and whether the focusing is accurate directly affects the integrity of the processed structure. An image focusing technique of inserting a focusing light source and an object in the optical path temporarily is proposed. By adjusting the position of the object to make its imaging plane consistent with the laser focusing plane, the laser focusing state is indirectly reflected through a clearly distinguishable imaging state. The original femtosecond laser optical path and the focusing optical path with a focusing light source and an object added are simulated and analyzed using the Zemax software. The two can achieve the same working distance behind the processing objective lens and good imaging quality, proving the feasibility of this method. Through analysis, it is obtained that the imaging error in this process is mainly caused by the depth of focus (3.9 μm) of the imaging lens, and the ideal focusing accuracy we obtained can reach within 1/2 of the depth of focus. A two-layer cylindrical structure with a single-layer height of 5 μm is designed. Through multiple experiments, it is verified that the height error of the processed element is within the range of 1.5 μm, which is consistent with the theoretical analysis and meets the focusing requirements of the femtosecond laser system.

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.