基于平面靶标的交叉结构光标定方法

High-precision cross structured light calibration method based on planar target

为实现线结构光高精度标定,提出一种基于平面靶标的交叉结构光标定方法。根据Blinn-Phong光照模型可知,当激光条纹投射在平面靶标上特征点边缘处时光截面不再服从高斯分布,常用的中心提取算法无法准确提取目标。首先,基于形态学操作剔除在平面靶标上特征点边缘处的中心点,使得直线拟合的误差由0.060 8 pixel提升到0.035 8 pixel,有效减少因算法提取误差对标定结果造成的影响;然后,基于高斯曲线拟合方法对所提取的线结构光与辅助结构光交点位置进行修正,基于Ransac算法进行直线拟合,结果同样也有效剔除因光照不均、材质变化造成误差较大的点。实验结果表明,两种方法结合后标定精度提高25%,中心点三维坐标与标定板平面方程相差仅4 μm,有效提高线结构光标定精度。

A cross structured light calibration method based on planar targets is proposed to achieve high-precision calibration of line structured light.According to the Blinn-Phong lighting model,it can be inferred that when the laser stripe is projected on the edge of the feature point on a planar target,the cross-section no longer follows a Gaussian distribution,the commonly used center extraction algorithm cannot accurately extract the target.Firstly,morphological operation is used to remove center points at the edges of feature points on flat targets,reducing the error of line fitting from 0.0608 pixels to 0.0358 pixels,effectively reducing the impact of algorithm extraction errors on calibration results.Secondly,based on Gaussian curve fitting method,correcting the intersection position of the extracted line structured light and auxiliary structured light,based on the Ransac algorithm for line fitting,the results also effectively eliminate points with significant errors caused by uneven lighting and material changes.Experimental results show that the combination of the two methods improves calibration accuracy by 25%,the difference between the three-dimensional coordinates of the center point and the plane equation of the calibration plate is only 4μm,effectively improve the accuracy of line structure cursor positioning.