关键词: 飞秒激光直写系统, 调焦技术, 光学设计, 模拟分析, 加工精度

Abstract: 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.

Key words: femtosecond laser direct writing system, focusing technology, optical design, simulation analysis, precision