Importance

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Abstract

Illumination for the platen of a finger receiving imaging prism is provided from a source mounted below the prism and reflected to the platen surface at an angle greater than the critical angle, through a beam folding input prism that is positioned primarily below and behind a front edge of the platen. Transmitting and scanning optics of the system are positioned behind and below the imaging prism, and an output prism is bonded to the imaging prism to receive light reflected from the platen, to shift the path of this reflected light downwardly and to direct it rearwardly toward system optics. The beam from the output prism is fed through an F-Theta scanning lens to a scanning mirror mounted on a scanning galvanometer that causes the fingerprint image to precisely scan across a linear array of print camera sensors that are repetitively sampled to provide a readout of the entire surface of the prism platen for reading a slap print. For a roll print, a portion of the beam is sent to a linear array of sensors of a roll camera to provide an estimate of position of the line of contact of the finger during its rolling motion over the platen. The estimate controls the galvanometer and scan mirror to align the image of the line of contact of the rolling finger precisely with the linear array of the print camera sensors.

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First Claim