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...http://www.google.com.tw/patents/US5812252?utm_source=gb-gplus-share專利 US5812252 - Fingerprint--Acquisition apparatus for access control; personal weapon and other systems controlled thereby 
