航空变焦距镜头非线性畸变快速校正方法  

Rapid Nonlinear Distortion Correction of Aerial Optical Zoom Lens System

作　　者：周前飞[1,2] 刘晶红[1] 

机构地区：[1]中国科学院长春光学精密机械与物理研究所,吉林长春130033 [2]中国科学院大学,北京100049

出　　处：《光学学报》2015年第4期139-152,共14页Acta Optica Sinica

基　　金：吉林省重大科技攻关项目(11ZDGG001);装备预研项目(402040203);国家林业公益性行业科研专项(201204515)

摘　　要：针对航空变焦距镜头的非线性畸变随焦距变化而变化的问题,提出一种地面离线标定和机上在线校正相结合的快速校正方法。利用单参数除式模型校正镜头畸变,根据模板图像中共线点的投影不变性,采用变步长优化搜索方法求解出若干离散焦距下镜头的畸变系数和畸变中心坐标,分析了畸变参数随焦距变化的规律,建立了畸变参数与焦距之间的经验公式。在飞行实验中,将实际工作焦距值代入经验公式得到相应畸变参数对实景图像进行自动校正。对模板图像与实景图像的校正结果表明,该方法能有效校正变焦距镜头的非线性畸变,对3幅不同焦距下的720 pixel×576 pixel模板图像校正平均均方差约为2.68 pixel,平均校正时间约为4.82 s。该方法具有效率高,便于自动化实现和工程应用的优点。Concerned with the nonlinear distortion problems varying with the focal length of aerial optical zoom lenses, a rapid geometric correction method based on combining the offline calibration on the ground with the online correction on board is presented. The one- parameter division model is adopted to correct the radial nonlinear distortion of lens. According to the perspective projection invariance of collinear points in template images, an optimization searching method of variant step length is adopted to estimate the optimal distortion coefficients and the distortion center coordinates of zoom lenses on the conditions of a few discrete focal lengths.The variation laws of the distortion parameters with the focal lengths are discussed by experiments finding, and the corresponding empirical formulas are established. In the actual flight test, the distortion parameters corresponding to the actual measured focal length value are calculated based on the empirical formulas to correct the lens distortion in the real scene images. Correction results of the template images and the real scene images show that this method can effectively correct the nonlinear distortion of zoom lenses. The average root mean square error of three 720 pixel×576 pixel images of template at different focal lengths is about 2.68 pixel, and the average correction time is 4.82 s. This correction method has the advantage of high efficiency, and easy to realize automatic correction for engineering applications.

关 键 词：成像系统 畸变校正 除式模型 变焦距镜头 摄像机标定 

分 类 号：V248.1[航空宇航科学与技术—飞行器设计]