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Infrared photography
>No, Clay, I did not say that the flesh RADIATED near IR. (it does, but only
>a very tiny amount.) The identification system I describe would probably
>use 940 nm IRLEDs to illuminate the face, and a silicon CCD detector to pick
>up the images. Or it would use ambient near-IR, perhaps from the sun or a
>tungsten filament or fluorescent lighting, along with an IR filter to ensure
>that the CCD camera picked up only the IR bands of interest. It would be
>easy to check out the results: Put such an IR-passing filter in front of a
>CCD-based camcorder, and take a picture of somebody.
>
>Incidentally, this simplicity shows the flaw in using this kind of system as
>an identifier: Since people's faces are usually visible, and can be
>photographed in the near-IR surreptitiously, it isn't clear how to prevent
>faking a face which appears to have the same IR signature and pattern.
I remember in a booklet from Kodak on their Ektachrome IR film, there was a
picture
of a forearm where all the veins were made clearly visible. This film is near
infrared (if I remember, the red color on the film corresponds to around
1100 nm).
Veins and artery identification might be possible, maybe, since fingerprint
identification is possible. A friend of mine developped a quite functionnal
algorithm doing just that in the late eighties. OTOH, the blood vessels
patterns are probably much more constant, from individual to individual,
than fingerprints. Just correct me if I am wrong.
JFA
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