BigPatents India

To discriminate a non-anticorrosive rolled material from an anticorrosive rolled material. [MEANS FOR SOLVING PROBLEMS] A method for discriminating a rolled material, comprising irradiating the surface of a rolled material as a discrimination object with light in an inclined irradiation direction, the light vibration direction being regulated in one direction, receiving light reflected from the rolled material surface through a polarizing element in which the direction of light reception is inclined to the rolled material surface and the direction of polarization to the direction of vibration of light applied to the rolled material surface is shifted, and discriminating whether the rolled material is a non-anticorrosive rolled material or an anticorrosive rolled material, based on the light reception amount.