Patent ID: 7108120
Filing Date: 2006-09-19
Classification: G07D

Abstract:
1. A method of inspecting a coin thrown into a machine, comprising the steps of: (a) arranging an exciting coil in the vicinity of one side of a coin passage inclined at a predetermined angle so that magnetic poles thereof face the coin passage; (b) arranging two receiving coils having substantially identical characteristics in the vicinity of said one side of said claim passage to be electromagnetically connected with said exciting coil and electrically connected to a differential amplifier so that the differential amplifier receives a differential input from said receiving coils; (c) exciting said exciting coil to oscillate at such a frequency that said two receiving coils detect an influence of a reactive magnetic field caused by eddy current induced on a surface of the thrown coin when the coin passes through an electromagnetic field produced by said exciting coil and issue electromotive force signals representing the influence of said reactive magnetic field as the differential input to said differential amplifier to determine a surface pattern of the thrown coin; and (d) discriminating authenticity of the thrown coin based on a combination of an output of said differential amplifiers and at least one of amplitude, frequency and phase of an oscillation voltage of said exciting coil.