Checking objects including bistable magnetic devices, to be chec

Details Checking objects including bistable magnetic devices, to be chec Checking objects including bistable magnetic devices, to be chec

1995-06-05

1996-12-10

Hajec, Donald T.

Registers

Records

Magnetic

902 28, G06K 1906

Patent

active

055833330

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.

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patent: 5204526 (1993-04-01), Yamashita et al.
patent: 5434917 (1995-07-01), Naccache et al.

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