基于多重差分滤波效应的航空相机图像检焦方法

Image Focusing Method Based on Multiple Differential Filtering Effects for Aerial Cameras

焦面检测准确与否对航空相机光学系统的成像质量起着至关重要的作用。为解决航空相机检焦问题,提出了一种基于多重差分滤波效应的检焦算法。首先,对检焦原理进行了介绍,在基本矩形滤波器的基础上进行设计,提出了一种适用于航空相机检焦的新型滤波器,消除了图像和滤波器之间相对位移产生的影响,并从数学角度证明了其可行性。然后,通过对图像的隔行采样对滤波器进行模拟,以完成图像检焦算法的设计。最后,利用实验采集的图像对所提算法的检焦效果进行了评估。实验结果表明,所提算法可以消除矩形滤波器和图像之间相对位移产生的正弦变化;算法灵敏度较高,最大误差为41.16μm,小于光学系统的半焦深(76.8μm),能够满足工程需求。

The imaging quality of the optical system in an aerial camera is significantly affected by the accuracy of focal plane detection.To resolve the focusing problem of aerial cameras,a focusing algorithm based on multiple differential filtering effects is proposed.First,the principle of focusing is expounded.With the basic rectangular filter as the design basis,a new filter suitable for focusing of aerial cameras is proposed to eliminate the influence of the relative displacement between the image and the filter,and its feasibility is proved from a mathematical point of view.Then,the filter is simulated by interlaced sampling of the image to complete the design of the image focusing algorithm.Finally,the images collected in the experiment are used to evaluate the focusing effect of this algorithm.The experimental results show that the proposed algorithm can eliminate the sinusoidal change caused by the relative displacement between the rectangular filter and the image.The proposed algorithm is able to meet engineering requirements with high sensitivity and a maximum error of 41.16μm,which is smaller than the half focal depth(76.8μm)of the optical system.