Patent ID: 8203448

Claim:
An foreign object detecting apparatus in bill passageway( 20 ), which is arranged in a bill validator and used to detect the presence of a foreign object in a bill passageway( 16 ), the bill passageway( 16 ) has a top side( 161 ), a bottom side( 162 ), a first lateral side( 163 ) and a second lateral side( 164 ) opposite to the first lateral side( 163 ), the foreign object detecting apparatus in bill passageway( 20 ) comprising: a laser light source( 22 ) arranged in the first lateral side( 163 ) to emit a coherent laser beam toward the second lateral side( 164 ) only; a first light detector( 24 ) arranged in the second lateral side( 164 ) to receive the coherent laser beam and to measure the intensity of the coherent laser beam; and a second light detector( 26 ) arranged in one of the top side( 161 ) and the bottom side( 162 ), wherein after a bill ( 100 ) passing through the bill passageway ( 16 ), if there is nothing in the bill passageway ( 16 ), the first light detector ( 24 ) can measure a predetermined intensity of the coherent laser beam ( 30 ) and the second light detector ( 26 ) can not detect any light; when a foreign object is presence in the bill passageway( 16 ), the intensity of the coherent laser beam received by the first light detector( 24 ) is decreased by the blocking of the foreign object, and at least a portion of the coherent laser beam which is reflected, refracted, diffracted or scattered by the foreign object is received by the second light detector( 26 ).