中文摘要：

为Nd：YAG激光打标机设计了变焦距f-theta镜扫描系统，以使它适用于不同的打标面积而不必更换镜头，系统由四片透镜组成，材料分别为BK7、SF18和SF11，系统总长度为122．96mm，工作波长1064nm。利用f-theta镜的负畸变效应和机械变焦原理，将四片镜设计组合成两个可变档系统，系统的有效焦距分别为f-theta镜的两个常用焦距：350mm和400mm，相应的扫描范围分别为220mm×220mm，250mm×250mm，扫描角都为±18°。系统像面在0视场、0．7视场和全视场的光斑都落在相应的爱里斑以内，系统的MTF曲线接近相应的衍射极限曲线，最大波像差小于四分之一波长，系统的最大场曲和最大f-theta相对畸变都很好地满足了国内激光打标机的精度要求。

英文摘要：

A varifocal f-theta lens was designed for Nd：YAG laser making scan focusing system, so that it apply to differ making area but change a lens necessarily. The system consists of four lens, made by glass BK7, SF18 and SF11. The total length of the system is 122.96mm, working at 1064m. Using the minus aberration of f-theta lens and machine zoom principle ,the three alterable focus system was designed. The two effective focal lengths of the system are 350ram and 400mm, which are usually used in f-theta lens. The scanning field is 220ram × 220mm,250mm × 250ram, respectively. All of the scanning angles are ± 18°. For these two effective focal lengths ,the spots on the image surface at zero view field,0.7-view field and full view field are all inside the airy disc. The system MTF curve of each effective focal length are accordance with the corresponding diffraction limits curve. The biggest wave aberration is smaller than 1/4 wave lengths. The maximum field curvature and maximum f-theta system distortion respectively satisfies the precision demand of the laser marking machine in China.