设计了一个相对口径为1/5、焦距为5 mm、视场角为125°的大视场针孔物镜系统。该结构在50 lp/mm时的所有视场的调制传递函数均大于0.5, 成像达到衍射极限, 但全视场畸变率达到-46%。根据光学成像理论和图像处理技术, 利用点阵样板计算光学中心和畸变系数, 建立畸变校正模型, 设计畸变校正算法。将线性成像模型与畸变校正模型相结合, 建立畸变校正率标定方程, 利用该算法求得的畸变校正率达到96.17%。将该校正方法与其他方法进行了对比分析, 结果表明, 该方法简单易行, 基本满足工业上的需求, 能够广泛适用于大视场镜头的成像畸变校正。

An optical system of pin-hole objective lens with large field is designed with relative aperture of 1/5, focus length of 5 mm and field angle of 125°. In this structure, the modulation transfer function for all fields is bigger than 0.5 at 50 lp/mm, and the imaging reaches the diffraction limit, but the full field distortion rate reaches -46%. According to optical imaging theory and image processing technology, the lattice template is used to calculate the optical center and the distortion coefficient. The distortion correction model is built and distortion correction algorithm is designed. With a combination of linear imaging model and distortion correction model, the calibration equation of distortion correction rate is built. The distortion correction rate obtained by this algorithm is 96.17%. This calibration method is compared with other methods, and we find that the proposed method is simple and practicable. The proposed method basically meets the needs of industry, and it can be widely used in image distortion correction of large field lenses.