The uneven reflective metal surface has great influence on the high-precision measurement of the structured light 3-D shape. By analyzing the laser scattering and reflection models, a set of light stripe center’s subpixel extraction methods which has strong robustness is proposed. The method first cuts off the influence of the uneven fixed background by using the difference image method to process the bright field and the dark field. Then, the regional growth statistics method is used to eliminate the influence of random laser speckle noise, and then the gray-gravity method is used to obtain the coarse center of the laser stripe. The Sobel operator is used to obtain the gradient vector of the stripe pixel point, and then the normal direction field of the light stripe is obtained. The normal direction field vector is taken as the direction to find the $5\times5$ neighborhood of the coarse light stripe’s center, and then the gray-gravity method is reused to determine the center position of the laser stripe in the normal line direction; the pixel coordinates of the subpixel level are obtained by using bilinear interpolation. The experimental results show that the method can effectively eliminate the interference of flash point noise and has strong robustness. The detection error of the stripe is less than 0.1 pixels, which ensures the system measurement accuracy. Compared with other methods, the system’s resolution can reach 0.02 mm.

中文翻译：

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几何测量中金属表面不均匀散射条件下的激光条纹中心检测

不均匀的反射金属表面对结构光3-D形状的高精度测量有很大影响。通过对激光散射和反射模型的分析，提出了一套鲁棒性强的光条中心子像素提取方法。该方法首先采用差分图像法对明场和暗场进行处理，切断不均匀固定背景的影响。然后，采用区域增长统计方法消除随机激光散斑噪声的影响，再采用灰度-重力法获得激光条纹的粗中心。使用Sobel算子得到条纹像素点的梯度向量，进而得到光条纹的法线方向场。以法线方向场矢量为方向，寻找粗光条中心的$5\times5$邻域，再利用灰度-重力法确定激光条在法线方向的中心位置；使用双线性插值得到亚像素级的像素坐标。实验结果表明，该方法能有效消除闪点噪声的干扰，具有较强的鲁棒性。条纹检测误差小于0.1个像素，保证系统测量精度。与其他方法相比，该系统的分辨率可达0.02 mm。使用双线性插值得到亚像素级的像素坐标。实验结果表明，该方法能有效消除闪点噪声的干扰，具有较强的鲁棒性。条纹检测误差小于0.1个像素，保证系统测量精度。与其他方法相比，该系统的分辨率可达0.02 mm。使用双线性插值得到亚像素级的像素坐标。实验结果表明，该方法能有效消除闪点噪声的干扰，具有较强的鲁棒性。条纹检测误差小于0.1个像素，保证系统测量精度。与其他方法相比，该系统的分辨率可达0.02 mm。