Patent ID: 6697516
Filing Date: 2004-02-24
Classification: G01N

Abstract:
A method for inspecting a surface of a moving strip to detect surface defects, comprising:forming 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; and processing the at least one filtered digital picture to identify a type of surface defect corresponding to each detected irregularity, wherein, prior to the processing step, an overall characterization of each of the irregularities is performed by determining, a value of predetermined parameters characteristic of surface defects, and a prior classification of the irregularities is performed based on the determined values of the parameters, according to a set of predefined classes, the processing step being performed on each class, wherein the processing step is specific for each class, wherein the predetermined parameters characteristic of the surface irregularities is less than a total number of parameters used to identify the defect, wherein, each predetermined parameter representing a general reference axis in a space whose dimensions correspond to the parameters, regions which each correspond to one of the predefined classes are delimited in the space, prior to the prior classification, each irregularity is represented in the space by a point whose coordinates are the values of the parameters, and the prior classification is performed by identifying the region to which each point belongs, and by assigning the corresponding irregularity to the class corresponding to the region, and wherein a simplified reference frame for representing the irregularities is determined for each region, a number of axes of which is less then a number of general reference axis, and subsequent to the prior classification step, changing a reference frame from the general reference to the simplified reference frame specific to the region to which the irregularity belongs for each irregularity represented.