| 摘要 |
PURPOSE:To accomplish a copy impossible system by a copying machine for preventing securities such as a stock and a bond, etc., important documents such as a contract and a letter of attorney, etc., and confidential documents from being forged by use of a copying machine. CONSTITUTION:The pattern constituted of the design of a prescribed motif, or characters, etc., is printed on the suitable position of a sheet as a copying original 31 by treatment liquid, a watermark having enhanced light transmittivity is formed, and at the time of copying, the difference of the transmitted light quantity between the watermark part and the part other than the watermark part is read by an optical sensor 22 incorporated with the copying machine, and when the prescribed difference is detected, the function of the copying machine is stopped. Thus, the sheet as the copying original 31 is surely detected by the optical sensor 22, and also an inconspicuous watermark is formed, and the copying machine is set so that a copying operation may be stopped when the watermark is detected by the copying machine, then, copied sheets other than the necessary sheets cannot be obtained by forming the watermarks on necessary sheets such as the confidential documents and the important documents. |
