Study on a new method for detecting flatness defects of hot rolling strip

A new non-contact method for detecting the flatness of hot rolling strip, which is based on laser, CCD and digital image processing technology is presented. This new method projects linear lasers to the strip at some angle between 20 degree to 30 degree from the length and width direction of strip to become the latitudinal and longitudinal lines, and then uses one or several cameras to pick images of strip surface containing linear laser lines. The 3D curves are restored from the picked images containing 2D laser lines, and then the 3D surface of strip are built by the restored 3D curves, finally the flatness of strip is obtained based on the 3D surface. The paper explains the measuring principle, the component of system and the implementation in detail. During the implementation, mathematical model and adjustment of camera, system calibration, image processing, restoring 3D curves, surface fitting, and analysis of flatness across the strip width are discussed.