Patent DE-102012207045-A1 (DE)
Title: Image processing apparatus, useful for detecting a shape of a weld bead, comprises a reference line laying unit for laying reference lines, a contour point image unit forming contour points at locations, and a midpoint formation unit
Inventor: ISHIDA HIDENOBU
IPC: B23K26/21
Filed: 2012-04-27
Abstract: The image processing apparatus comprises a reference line laying unit for laying reference lines in such a way that it corresponds to an image of a welded portion, which is detected and recorded while a residue thermo-luminescence is produced at the welded portion during laser welding; a contour point image unit for forming contour points at locations, at which the reference lines cross a boundary, where a luminance threshold level is adjusted to characterize a contour line of a weld bead (m); and a midpoint formation unit for forming a midpoint. The image processing apparatus comprises a reference line laying unit for laying reference lines in such a way that it corresponds to an image of a welded portion, which is detected and recorded while a residue thermo-luminescence is produced at the welded portion during laser welding; a contour point image unit for forming contour points at locations, at which the reference lines cross a boundary, where a luminance threshold level is adjusted to characterize a contour line of a weld bead (m); a midpoint formation unit for forming a midpoint between each two of the contour points on the same reference line; and a contour line image unit for forming the contour line on the basis of the contour points. The boundary is placed between an area, in which a luminance of the residue thermo-luminescence in the recorded image is higher than a luminance threshold level, and an area, in which a luminance of the residue thermo-luminescence is lower than the luminance threshold level. The weld bead is formed at the welded portion by the laser welding on the basis of the image of the welded portion. The image processing apparatus further comprises: a midline formation unit for forming a midline on the basis of midpoints and for forming a midline of a shape of the weld bead on the basis of an adapted curve for weld bead range points in such a way that it corresponds to the image, which is received with the weld bead range points before the reference lines are put, where the weld bead range points exceed the luminance threshold level; a contour point detection unit for detecting a curvature of the midline before the contour line is formed, and, if more than two contour points are formed on the same reference line, for determining two contour points that are on the other side on the same reference line with a distance between the contour points extending itself over the weld bead opposite to form the midpoints; a reference line adapter unit for adapting the reference line having a portion parallel to a curved shape of the midline; and a contour point selection unit, which is arranged in such a way that, before the midpoints are put, a segment length is calculated between each two of the contour points on the same reference line, a frequency distribution of the segment lengths is calculated, a breadth of the weld bead is calculated on the basis of the weld bead range points, which exceed the luminance threshold level, and a long segment related to a highest segment value, which is defined on the basis of the breadth of the weld bead and a short segment related to a lowest segment value, which is defined on the basis of the breadth of the weld bead are distinguished using the frequency distribution. The contour points are located at both ends of the long and short segments. The two contour points are used to form the midpoints and the contour line. The highest segment value for discriminating the long segment corresponds to a double breadth of the weld bead, and the lowest segment value for discriminating the short segment corresponds to a half breadth of the weld bead. An independent claim is included for an image processing method for detecting a shape of a weld bead formed at a welded portion by laser welding on the basis of an image of the welded portion.