To determine a normal printed matter and a copied one of printed matters with high accuracy.
An embedding printer P prints a correlation type electronic watermark in print data (step S11). Next, the normal printed matter to be reference is selected (step S21), a test normal printed matter is selected (step S22), an acquiring device S acquires these images (step S23), and a discrimination threshold T_ps is calculated on the basis of detection strength of electronic watermark detected from the acquired image data (step S24). The acquiring device S acquires images about printed matters of a determination target by using the discrimination threshold T_ps (step S31), reliability is calculated on the basis of the detection strength of the electronic watermark, the reliability is compared with the discrimination threshold T_ps to determine the authenticity of the printed matter.
Tadashi Takahashi
Takashi Watanabe
Masakazu Aoyama
Suzuki Mitsuyoshi
Yasuhiko Murayama