Patent ID: 11852458

Abstract:
An oxide layer thickness measurement device according to the present invention stores, for each of layer thickness measurement sub-ranges constituting a layer thickness measurement range, layer thickness conversion information representing a correlation between a layer thickness and an emissivity where a ratio of a change in the emissivity to a change in the layer thickness in the layer thickness measurement sub-range falls within a set extent. Emitting light luminances of a surface of a steel sheet are measured at respective measurement wavelengths different from each other, and a temperature of the surface of the steel sheet is measured to thereby calculate the emissivity at each of the measurement wavelengths. Calculated in connection with the emissivity calculated at each of the measurement wavelength are the layer thickness corresponding to the emissivity at the measurement wavelength, and a ratio at the layer thickness by using the layer thickness conversion information corresponding to the measurement wavelength. The calculated thickness is extracted as a candidate value for an actual layer thickness when the calculated ratio is within the preset extent assigned for the layer thickness conversion information.