SCANNERS FOR READING NEAR INFRARED FLUORESCENT MARKS

摘要

An apparatus for detecting an invisible, near infrared fluorescing mark disposed on a background comprises: an excitation source for exciting the mark, the source having sufficient power to provide a fluorescent signal from a mark situated on at least reflective portion of the background; signal detecting means for detecting the fluorescent signal from the mark; and power modulating means for varying the power between zero and the maximal power level of the excitation source, which is preferably a laser, in a manner effective to produce a decodable fluorescent signal from a mark disposed on any portion of the background. A process for decoding an invisible mark comprising a near infrared fluorescing material comprises: providing at least one invisible, near infrared fluorescing mark disposed on at least one portion of a background; exciting the mark with a laser having a maximal power level sufficient to provide a fluorescent signal from the mark when it is disposed on at least reflective portion of the background; and detecting the fluorescent signal and concurrently varying the power of the laser between zero and its maximal power, thereby obtaining a decodable fluorescent signal at a laser power level between zero and the maximal of a mark disposed on any portion of the background.