Finger surface image enhancement having liquid layer on finger t

Details Finger surface image enhancement having liquid layer on finger t Finger surface image enhancement having liquid layer on finger t

1991-07-11

1993-01-05

Nelms, David C.

Radiant energy

Photocells; circuits and apparatus

Optical or pre-photocell system

250556, 356 71, H01J 516

Patent

active

051773538

ABSTRACT:
A layer of liquid, such as alcohol, water or a mixture thereof, on the finger touching surface of a platen provides an image in an optical fingerprint imaging system which assures valley and ridge definition and continuity by virtue of the liquid filling in the cracks and holes in the ridge zone, by creating an air pocket in the valley zone that holds the valleys open and by otherwise interacting with the finger to reinforce the distinction between valley and ridge zones in the optically imaged picture. 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. The technique is useful for roll prints and touch prints.

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