变形模板匹配的圆标靶中心点优化方法

Optimization method of center point of circular target based on deformation template matching

针对近景摄影测量常用的圆形标靶的中心点进行识别和定位时,如何提高圆标靶中心点提取的精准度问题,该文提出了一种基于变形模板匹配的优化方法,对初步识别的中心点做进一步优化,以此获得精准的标靶中心。该方法首先利用物体在相机中的成像特点,模拟标靶成像时的状态,构造一个与目标所成之像高度相似的变形模板影像;然后以影像间的相关系数作为匹配测度,用这个模板在原始影像上进行滑动匹配,寻找到相关系数最大时的模板中心点坐标作为优化后的标靶中心点坐标;最后通过改变滑动的步距可将优化精度提升到子像素级。实验结果表明,优化后的标靶的中心点的精确度得到了明显的提高。

In the process of identifying and locating the center point of a circular target commonly used for close-range photogrammetry,the accuracy determines the quality of the measurement.In order to improve the accuracy of the extraction of the center point of the circular target,this paper proposes an optimization method based on the deformation template matching,and further optimizes the initially identified center point to obtain a precise target center.The method firstly uses the imaging characteristics of the object in the camera to simulate the state of the target imaging,constructs a deformed template image that is highly similar to the image formed by the target.Then uses the correlation coefficient which between the images as the matching measure,and uses this template in the sliding matching is performed on the original image,and the coordinate of the template center point when the correlation coefficient is maximum is found as the coordinate of the optimized target center point.Finally,the optimization precision is improved to the sub-pixel level by changing the sliding step.The experimental results show that the accuracy of the center point of the optimized target is significantly improved.