Importance

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Abstract

At a first end of an optic-fiber prism assembly are fiber terminations to contact a relieved surface, e. g. finger (stabilized by a handgrip). In a region where fiber diameter is essentially constant with longitudinal position, light enters the prism, crosses the fibers and enters individual fibers through their sidewalls, lighting the terminations. To allow crosslighting of the assembly, the fiber-optic numerical aperture (NA) is small: preferably not exceeding one-half. Due to fingerprint etc. detail, fractions of light pass along the fibers; at the assembly second end a detector responds with an electrical-signal array based on the surface relief. The signals are processed to check finger etc. identity and applied to control access to a personal weapon, other equipment, facilities, data, or a money service. FTIR ('frustrated total internal reflection') bright- and dark-field versions have various benefits. For use of small, low-cost detectors--and/or internal-mirror versions that light the finger straight-on--the assembly has a separate element, e. g. a high-NA fiber-optic taper with extramural absorption or 'EMA' material (no entry light crosses it). For a weapon, a unitary antibypassing module (which matches a weapon port, and must be present) holds part of the access-control and firing systems. Bullets etc. fire only on a special signal from the module.

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First Claim