Patent ID: 7471400

Claim:
An electric resistance welded pipe bead shape detecting method, for detecting the bead shape of an electric resistance welded pipe, wherein an image, obtained by a slit light being irradiated or a point light being scanned on a pipe surface including a bead portion due to welding of an electric resistance welded pipe, and an image of the slit light irradiated on the pipe surface including the bead portion or an image of the track of the point light scanned thereupon being taken with image-taking means from an angle different to the irradiation direction of slit light, is subjected to predetermined image processing; said method comprising: a step for obtaining shape data of a portion of the pipe surface equivalent to the bead portion from shape data of the pipe surface including the bead portion calculated in said image processing, from preset boundaries at the left and right edges of the bead portion, and an apex position of the bead portion calculated separately; a step for dividing said shape data of the portion of the pipe surface equivalent to said bead portion into two regions, left and right; a step for performing approximation with a function with regard to each of the left and right shape data, so as to obtain approximation functions for the left and right bead shapes; a step for performing further approximation with a function, with regard to base pipe shape data excluding the pipe surface shape data of the portion equivalent to said bead portion from the shape data of the pipe surface including the bead portion, so as to obtain base pipe shape approximation functions; and a step for calculating at least one of the width, height, slope angle, and step at the left and right boundaries between the bead portion and base pipe, based on each of said left and right bead shape approximation functions, and said base pipe shape approximation function.