title: Sub-Pixel Extraction of Laser Stripe Center Using an Improved Gray-Gravity Method.
abstract: Laser stripe center extraction is a key step for the profile measurement of line structured light sensors (LSLS). To accurately obtain the center coordinates at sub-pixel level, an improved gray-gravity method (IGGM) was proposed. Firstly, the center points of the stripe were computed using the gray-gravity method (GGM) for all columns of the image. By fitting these points using the moving least squares algorithm, the tangential vector, the normal vector and the radius of curvature can be robustly obtained. One rectangular region could be defined around each of the center points. Its two sides that are parallel to the tangential vector could alter their lengths according to the radius of the curvature. After that, the coordinate for each center point was recalculated within the rectangular region and in the direction of the normal vector. The center uncertainty was also analyzed based on the Monte Carlo method. The obtained experimental results indicate that the IGGM is suitable for both the smooth stripes and the ones with sharp corners. The high accuracy center points can be obtained at a relatively low computation cost. The measured results of the stairs and the screw surface further demonstrate the effectiveness of the method.
authors.affiliation: School of Mechanical Engineering, Hebei University of Science and Technology, Shijiazhuang 050018, China. yuehua.hrbin@163.com.
authors.forename: Yuehua
authors.initials: Y
authors.lastname: Li
authors.affiliation: School of Mechanical Engineering, Hebei University of Science and Technology, Shijiazhuang 050018, China. zhoujingbo@hebust.edu.cn.
authors.forename: Jingbo
authors.initials: J
authors.lastname: Zhou
authors.affiliation: School of Mechanical Engineering, Hebei University of Science and Technology, Shijiazhuang 050018, China. hfs_high@126.com.
authors.forename: Fengshan
authors.initials: F
authors.lastname: Huang
authors.affiliation: School of Mechanical Engineering, Hebei University of Science and Technology, Shijiazhuang 050018, China. liulijian2002@126.com.
authors.forename: Lijian
authors.initials: L
authors.lastname: Liu
keywords: adaptive sampling regions; improved gray-gravity method; line structured light sensor; sub-pixel center extraction; uncertainty analysis