| 摘要 |
A method and apparatus for determining a class signature from an article made of paper or cardboard in order to identify a generic type of class to which the article belongs. An optical beam illuminates the article and a detector arrangement collects data points from light scattered from many different parts of the article as the article is scanned by the beam. The class signature derives from intrinsic properties imparted to the paper/cardboard during manufacture by, it is believed, the screen used during dewatering of paper pulp; the class signature may be in the form of an invisible spatial modulation, such as chirped modulation, super-periodicity modulation, amplitude modulation, phase shift keying modulation or frequency shift keying modulation. Detection of the class signature allows the manufacturer or the particular paper making machine that made the paper to be identified. |
