Finger surface image enhancement having a liquid layer on the fi

Details Finger surface image enhancement having a liquid layer on the fi Finger surface image enhancement having a liquid layer on the fi

1990-07-31

1991-09-24

Nelms, David C.

Radiant energy

Photocells; circuits and apparatus

Optical or pre-photocell system

25022731, 356 71, H01J 516

Patent

active

050515764

ABSTRACT:
A layer of liquid, such as water, on the finger touching surface of a platen provides an image in a optical fingerprint imaging system which assures valley and ridge definition and continuity by virture of the water filling in the cracks and holes in the ridge zone and by creating an air pocket in the valley zone that holds the valleys open. Multiple interrogating light beams, each incident at greater than the critical angle on the finger touching surface of the platen assure imaging all minutia and that the valley zones in the image will be black.

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patent: 4925300 (1990-05-01), Rachlin

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