线结构光条纹中心的全分辨率精确提取

Accurately extracting full resolution centers of structured light stripe

激光条纹中心的提取是线结构光坐标测量系统的关键技术之一,本文对条纹中心的高分辨率精确提取进行了研究。首先,基于阈值法全分辨率提取条纹初值中心;然后,在条纹初值中心域应用灰度梯度与Bazen方法计算条纹法向,最后在法线方向精确获取光条纹能量中心。采用分辨率为768×576的相机,应用V形检测块进行对比实验,结果表明:提取的中心点分辨率为1 086点,比传统方法增加了42.5%,且无冗余点;中心点到由中心点拟合的直线的平均距离最小,分别为0.294与0.306 7 pixel;条纹法向计算精确,计算时间为75.8 ms。该方法避免了被测体表面曲率变化大、提取中心密度小等问题,提取的精度与鲁棒性高,满足在线精确测量要求。

Extracting the center of a stripe is one of the key techniques of a structured light measurement system. An approach to increase the extracting resolution for the centers of a laser stripe and the extracting precision is investigated. Firstly, full resolution initial centers of the light stripe is presented based a threshold algorithm. Then, the gray grades of the field along the initial points of the stripe are calculated with a Sobel operator,and the normal direction at the initial points of the stripe is calculated by the Bazen method. Finally, the energy centers of the stripe are accurately gained in the normal direction. A contrast experiment in the V-shaped test block with a camera in resolution of 768× 576 indicates that the resolution of the centers is 1086 dots without redundance, and the number of effective dots has increased by 42.5% as compared with that of barycenter method. In addition,the average distance between the extracting corners and the line fitted by the extracting centers is the shortest one, only 0. 294 and 0. 306 pixeh The proposed method can calculate exactly the normal direction of the stripe,and computing time is 75.8 ms. Experiments show that the approach can avoid a mini density for a large curvature surface of the measured object and can get full resolution centers,it is suitable for online accurate measurements.