| Popis: |
A system to thwart counterfeiting and copying of documents, ID's, passports, etc, is proposed, together with an optoelectronic system for rapidly and relatively inexpensively verifying the card or document. For highest security a biometric image is used. This is covered with an optical phase mask bonded tightly to the biometric tag, so that they can not be separated. The biometric tag and the phase mask are both authenticated by the reader to verify the person presenting the ID. The phase mask can not be read with incoherent light, since optical phase scatters the light into a random pattern. This eliminates such devices as CCD detectors, computer scanners, and photo-sensitive detectors. Only an optical interferometer could be used to read and copy the phase mask, and then only if it could be separated intact from the biometric tag. Two systems have been studied to verify the phase-mask and biometric tag. One is a conventional coherent optical correlator, usually referred to as the 4-f or frequency plane correlator. |
