基于亚像素边缘的摄像机标定板特征提取算法

目的在视觉测量领域,摄像机的标定精度是最终测量精确度的决定性因素,为了提高标定板特征的提取精度,提出一种基于亚像素边缘的提取方法。方法针对圆点标定板,首先采集标定板图像,对图像进行处理,获取像素级别边缘,然后以边缘像素点为中心,取3×3的数字窗口计算梯度方向,在梯度方向上进行像素点灰度的双曲正切拟合,获取亚像素级别边缘,最后对亚像素边缘按照圆形进行拟合,求得圆心坐标。结果实验表明算法的分辨率达到0.03个像素,精度可达0.1个像素。结论该算法具有稳定可靠,精度高,运算速度快等特点,能够应用于图像拼接和分割,特征提取和摄像机标定等领域。

Extraction Algorithm of Camera Calibration Board Feature Based on Sub-pixel Edge

The work aims to propose an extraction method based on the sub-pixel edge, in order to improve the extraction precision of the calibration board feature, as the camera calibration precision is the decisive factor in the field of vision measurement. Firstly, the calibration board image was acquired and processed to obtain the edge at pixel level regarding the dot calibration board. Then, 3×3 digital window was taken to calculate the gradient direction, taking the edge pixel as the center. The edge at sub-pixel level was obtained by gray level fitting in the gradient direction based on hyperbolic tangent. Finally, the center coordinates were acquired by the sub-pixel edge fitting according to the circle. The experiment showed that the resolution of the algorithm reached 0.03 pixels and the precision could reach 0.1 pixels. Characterized by stability, reliability, high precision and fast computing speed, the proposed algorithm can be applied in the field of image splicing and segmentation, feature extraction and camera calibration.