초록 ▼

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 degre

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.

대표청구항 ▼

[ What is claimed is:] [1.] An optical fingerprint imaging system comprising in combination:a platen having a finger-touching surface to which a liquid layer may be applied;means for providing two interrogating light beams, one on each side of and below the finger position on the platen and position

[ What is claimed is:] [1.] An optical fingerprint imaging system comprising in combination:a platen having a finger-touching surface to which a liquid layer may be applied;means for providing two interrogating light beams, one on each side of and below the finger position on the platen and positioned to illuminate and provide a modulated light beam from the ridges and valleys of the finger surface when immersed in the liquid layer and placed on the finger-touching surface of the platen;the two interrogating light beams each being collimated and the projections of each beam into a horizontal plane assuming an angle of approximately forty-five degrees with the longitudinal axis of the finger when place on the finger-touching surface;imaging means;a mirror for reflecting the visible modulated light beam from the finger ridges and valleys to the imaging means; and,a first polarizing filter positioned between the platen and the mirror to intercept the visible modulated light prior to reflection from the mirror.