DUPLICATE FEED DETECTING DEVICE

摘要

PROBLEM TO BE SOLVED: To provide a duplicate feed detecting device of a paper carrying device for allowing continuous printing, and preventing erroneous detection of a duplicate feed without interrupting printing once on paper different in the thickness by switching a hopper. SOLUTION: This duplicate feed detecting device detects the duplicate feed of the paper by inputting amplified output to a duplicate feed detecting part by amplifying the output of a light receiving element by an amplifier by oppositely arranging a light emitting element and the light receiving element in the paper carrying device for separately and continuously carrying a large number of paper one by one on a carrying passage by sandwiching the paper carried on the carrying passage, and is characterized by automatically switching an amplification factor of the amplifier in a plurality of stages by an amplification factor switching means according to the size of the output provided from the light receiving element when amplifying the output from the light receiving element. COPYRIGHT: (C)2004,JPO&NCIPI