Abstract: An apparatus for detecting an invisible, near infrared fluorescing mark disposed on a background comprises: includes an excitation source for exciting the mark, having sufficient power to excite the mark and provide a fluorescent signal the mark from a; a signal detector for detecting the fluorescent signal from the mark; a and power modulator means for varying the power if the excitation source between zero and the maximum power level to produce a decodable fluorescent signal from the mark disposed on the background. A process for decoding an invisible mark having a near infrared fluorescing material includes the steps of: 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 maximum power level sufficient to provide a fluorescent signal from the mark; detecting the fluorescent signal and concurrently varying the power of the laser between zero and its maximum power, to obtain a decodable fluorescent signal.