PURPOSE: To simply retrieve, control and input the information by writing the invisible identification information onto the visible informatin written in both the ink which can be recognized in a visible light area and the ink of the specific absorbing characteristic by combining together these two different types of ink.
CONSTITUTION: The visible light given from a projector 21 of an information reading part 11 is absorbed in the ink of the document printed on a hard copy 23, and the invisible light is absorbed by the identification information printed on the copy 23 respectively. The information is written into the copy 23 in the 2nd ink which consists of the black ink recognizable in a visible light area, the same colored ink that has the absorbing characteristic coincident with the black ink for the visible light, and the ink that has the light absorbing characteristic discordant with the black ink in every wavelength area other than the visible light area and also can be detected by an infrared beam sensor, for example. Under such condition, the print information is divided in a certain unit, and the code information of 0 or 1 is assigned for each unit. Thus the information visibly printed can include invisibly other information.
NAKAMURA HISATADA
INAGAKI MASATOMI
