| 摘要 |
<p>PURPOSE:To decide the existence of information regadless of the effect of the information on the rear side of a medium, by detecting the presence or absence of the print from the difference of concentration between the adjacent changing regions. CONSTITUTION:A concentration output that is obtained by scanning the characters, symbols, etc. printed on the surface of a medium by a picture detecting element 1 is sampled by a multivalue A/D converter 2 to obtain D1-Dn. Then D1-D2=X1-Dn-1-Dn=Xn-1 is calculated through a concentration difference calculating circuit 3 to obtain a difference X1-Xn-1 between the adjacent sampling outputs. Then each of X1-Xn-1 is compered with the set reference value through a comparator 4 to obtain an effective sampling value exceeding the set value. The print concentration of the effective sampling value is added through an adder 5 to obtain an added value A. This value A is divided by an effective sampling number B obtained through a counter 6 to obtain a mean value A/B. This value A/B is compared with the threshold value set previously through a comparator 10 to decide the presence or absence of the print. Thus the presence of information can be decided regardless of the effect of information on the rear side of the medium.</p> |
