[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

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


 PGP 2048 bits key at:     http://w3.citenet.net/users/jf_avon
 ID:C58ADD0D  52 96 45 E8 20 5A 8A 5E  F8 7C C8 6F AE FE F8 91 
 Unsollicited commercial e-mail will be proofread at US165 $/h
 Any sender of such material will be considered as to have ac-
 cepted the above mentionned terms.