一种光斑图像中心的亚像素提取方法

Sub-pixel Extraction Method for the Center of Light-spot Image

针对空间发光点所成光斑图像中心的高精度提取问题,本文提出一种亚像素提取方法。该方法建立了具有高斯能量分布的空间发光点的透视投影光斑图像灰度分布数学模型,证明了空间发光点能量中心的透视投影不变性。通过对光斑图像二阶方向导数和自相关函数的分析,获得Hessian矩阵并推导出像素级光斑图像中心的判定条件,再将图像灰度分布函数在光斑图像像素级中心的亚像素邻域内泰勒展开,并求取光斑图像灰度分布曲面的局部极大值点作为亚像素级光斑图像的中心点。与现有经典方法的对比仿真实验结果表明,该算法具有更高精度和更好的鲁棒性,可广泛应用于视觉检测的摄像机标定、三维形貌测量等任务中(类)光斑中心的高精度提取。

An extraction method in sub-pixel level was proposed to solve the high accuracy center point extraction problem of the light-spot image of the spacial light-emitting-spot. The gray level distribution mathematical model of the light-spot image of the spacial light-emitting-spot with Gauss energy distribution was established, as well as the proof was given for the perspective projection invariability of the spacial light-emitting-spot. Based on the analysis of the second-order directional derivatives and the self-correlation function of the light-spot image, the Hessian matrix was obtained which was used to derive the determinant terms for the pixel level center point. Furthermore, the Taylor expansion was performed on the image gray level within the sub-pixel neighborhood of the pixel level center point, and the maximum of the gray level curved surface of the light-spot image was taken as the wanted sub-pixel center point. Compared with the existing classical methods, the experiment results show that the proposed method has higher accuracy and better robustness which can be widely used in camera calibration and 3D shape measurement, etc.