Patent ID: 6778694
Filing Date: 2004-08-17
Classification: G01N

Abstract:
Method for inspecting a surface of a moving strip, to detect a surface defect, comprising:using a photographic means to form at least one digital picture of at least one face of the strip, the digital picture being made up of a set of successive rows of picture elements, each of which is assigned a digital value; filtering the at least one digital picture to detect surface irregularities by detecting relative variations in the digital values; segmenting the at least one digital picture into suspect zones such that each suspect zone contains a surface irregularity; and processing the suspect zones to identify a type of surface defect corresponding to each irregularity detected; wherein the segmenting the at least one digital picture comprises: calculating a first profile of the variation in the digital values of the picture elements in a first direction parallel to a direction of movement of the moving strip, thresholding the first calculated profile to define strips of picture elements which each have at least one surface irregularity, calculating for each strip defined a second profile of the variation in the digital values in a second direction separate from the first direction and perpendicular to the direction of movement of the moving strip, and thresholding the second calculated profile to define the suspect zones which each contain the surface irregularity, wherein the calculating the first profile includes calculating a sum of the digital values of columns of picture elements, and the calculating the second profile includes calculating for each strip a sum of the digital values of each of the rows of picture elements.