Importance

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Abstract

A scanning fingerprint reader provides a set of digital data representing interface topology of a fingerprint pressed against a platen (20). The platen (20) is formed by one surface of a prism (10) utilizing total internal reflection of an illuminating beam (30) directed at an interior surface of the prism. The beam (37) that is output from the prism is fed through a scanning lens (40) to a scanning mirror (48) that causes the fingerprint image (68) to scan across a linear array (60) of CCD sensors that is repetitively sampled to provide a print readout of the entire surface of the prism for reading a slap print. The signal from the CCD array is read out and digitized (72,74,76) to provide a serial bit stream (78) representing the set of multiple fingerprints on the platen. An optical architecture (40,48,56) employing dual telecentricity eliminates keystoning distortion. A portion of the beam is sent to a linear CCD array (94) of a roll print camera to provide an estimate of the position of the line of contact of the finger during its rolling motion over the platen. The estimate is used (52) to position the scan mirror (48) so that the image of the line of contact (98) of the rolling finger (100) is aligned with the linear array (70) of the print camera.

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First Claim