Patent ID: 7623226

Claim:
An optical method which detects defects of a hot traveling product having a temperature typically within the range of 600-1000° C. during hot-rolling, the method simultaneously detecting defects located on a surface and under the surface of the hot traveling product by the formation and processing of images of the hot traveling product, the images formed by a first portion from light emitted by the hot traveling product itself and for which the wavelength is in the infrared region and by a second portion from light reflected by the product and for which the wavelength is in the visible spectrum, the detection of the lights being provided by a plurality of linear sensors, each of the linear sensors being associated with the detection of an image, the method comprising: providing linear sensors collectively arranged relative to an objective of a camera, with each of the linear sensors being located in a different focal plane associated with a wavelength range in order to obtain superposable images; moving the linear sensors relative to the objective depending upon the wavelength of light forming an image to be recorded, each of the linear sensors being movable to a multiplicity of positions relative to the objective; and providing a defect detection signal obtained from the linear sensors.