Checking objects including bistable magnetic devices, to be checked for authenticity
First Claim
1. A checking object to be checked for authenticity, comprising:
- a base formed of a nonmagnetic material;
a scanning region located in a specific position of the base;
a number of bistable magnetic wires which have respective diameters and lengths which are within predetermined ranges, and said bistable magnetic wires being dispersed at random in the scanning region so as to be oriented in many and unspecified directions and which produce a Large Barkhausen effect, said bistable magnetic wires being adapted to undergo a drastic flux reversal attributable to the Large Barkhausen effect when subjected in succession to first and second external magnetic fields of opposite directions; and
a code indicator section, including a magnetically readable medium, provided in part of the base so that information for a proper flux reversal responsive to said bistable magnetic wires within the scanning region is encoded and recorded in the code indicator section by use of said magnetically readable medium.
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Abstract
A number of bistable magnetic devices are dispersed in a scanning region of a checking object. Each bistable magnetic device is formed of a nonmagnetic material which undergoes a drastic flux reversal attributable to the Large Barkhausen effect when subjected in succession to first and second external magnetic fields of opposite directions. A processing apparatus comprises magnetic generators for generating magnetic fields of opposite directions, a transportation mechanism for moving the checking object at constant speed, and a coil for detecting magnetic pulses, which are generated as the bistable magnetic devices are subjected to the flux reversal, as changes of electromagnetic induction voltage. A detection signal for the scanning region detected by the apparatus is converted into a cipher code and then recorded in a code indicator section of the checking object. In checking the authenticity of the object, the detection signal obtained by scanning the scanning region and a code for collation obtained by decoding the cipher code recorded in the code indicator section are compared, and it is concluded that the checking object is real when the detection signal and the collation code correspond to each other.
28 Citations
12 Claims
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1. A checking object to be checked for authenticity, comprising:
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a base formed of a nonmagnetic material; a scanning region located in a specific position of the base; a number of bistable magnetic wires which have respective diameters and lengths which are within predetermined ranges, and said bistable magnetic wires being dispersed at random in the scanning region so as to be oriented in many and unspecified directions and which produce a Large Barkhausen effect, said bistable magnetic wires being adapted to undergo a drastic flux reversal attributable to the Large Barkhausen effect when subjected in succession to first and second external magnetic fields of opposite directions; and a code indicator section, including a magnetically readable medium, provided in part of the base so that information for a proper flux reversal responsive to said bistable magnetic wires within the scanning region is encoded and recorded in the code indicator section by use of said magnetically readable medium. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A checking object to be checked for authenticity, comprising:
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a base formed of a nonmagnetic material; a scanning region located in a specific position of the base; a number of bistable magnetic wires which have respective diameters and lengths which are within predetermined ranges, and said bistable magnetic wires being dispersed at random in the scanning region so as to be oriented in many and unspecified directions and which produce a Large Barkhausen effect, said bistable magnetic wires being adapted to undergo a drastic flux reversal attributable to the Large Barkhausen effect when subjected in succession to first and second external magnetic fields of opposite directions; and a code indicator section, including an optically readable medium, provided in part of the base so that information for a proper flux reversal responsive to said bistable magnetic wires within the scanning region is encoded and recorded in the code indicator section by use of said an optically readable medium. - View Dependent Claims (8, 9, 10, 11, 12)
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Specification