METHOD FOR MARKING AND RECOGNIZING DOCUMENT

摘要

PROBLEM TO BE SOLVED: To provide a method for putting a mark which is invisible under ordinary visual conditions but can be detected under special conditions. SOLUTION: A marking material containing a Raman detectable component exhibiting Raman spectrum upon irradiation with monochromatic radiation is applied to a recording sheet thus putting a mark thereon. The mark on the recording sheet is then irradiated with monochromatic radiation and Raman spectrum is measured for the radiation scattered by the mark.