Finger surface image enhancement having a liquid layer on the finger touching surface of the platen
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United States of America Patent
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-
Sep 24, 1991
Grant Date -
N/A
app pub date -
Jul 31, 1990
filing date -
Jul 31, 1990
priority date (Note) -
Expired
status (Latency Note)
Importance
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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