Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Patent
1996-08-12
1998-04-07
Allen, Stephone B.
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
25022711, 356 71, 382124, 283 70, G02F 101, G06K 974, B42D 1500
Patent
active
057367345
ABSTRACT:
A fingerprint enhancement system has a platen with a liquid contacting and finger-touching surface. Two collimated interrogating light beams lie below and are opposite sides of the finger-touching surface. The horizontal extensions of the light beams assume an angle of approximately forty-five degrees with the finger longitudinal axis. Side surfaces of the platen are oriented normal to the incident colliminated light beams prior to interrogation. The light beam modulated by the fingerprint passes to a reflecting mirror, imaging means and a scanner below the platen. A polarizing filter lies between the platen and reflecting mirror. A second polarizing filter lies above the platen. A contrast enhancement circuit increases the modulation of the scanned fingerprint signal and automatically adjusts the level of the modulated signal without saturation. Circuit filtering eliminates spurious input signals. Finger position sensing by a light emitting diode and photo transistor is also provided.
REFERENCES:
patent: 3804519 (1974-04-01), Outeru et al.
patent: 4785171 (1988-11-01), Dowling, Jr. et al.
patent: 4975969 (1990-12-01), Tal
Chilcott William
Marcus Daniel H.
Pekcan Hakan I.
Schlang Arthur
Allen Stephone B.
Fingermatrix Inc.
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