Apparatus and method for authentication of documents printed with magnetic ink
AssigneeEastman Kodak Company
InventorFrederick J. Jeffers
Life of this patent
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Abstract
A detection system for detecting and/or verifying the magnetic properties of the magnetic ink layer on common printed or copied documents includes, in order of interaction with the magnetic ink of a Document, a saturation record head, a saturation read head, a non-saturation record head, and a non-saturation read head. The disclosed method of operation is equivalent to the normal testing of the magnetic layer of a Document, but eliminates the need for an erase magnet.
Claims16
A magnetic head array for detecting magnetic hysteresis properties of a magnetic layer, said array comprising:
- a first record head producing a D.C. magnetic field in said magnetic layer, said D.C. magnetic field having a strength sufficient to saturate said magnetic layer in a first direction;
- a first read head positioned proximate to and down stream from said first record head, said first read head detecting the phase and magnitude of remanent magnetization in said layer produced by said first record head;
- a second record head located proximate to and down stream from said first read head, said second record head producing a magnetic field in said magnetic layer which is opposite in direction to said D.C. magnetic field produced by said first record head, said magnetic field produced by said second record head demagnetizing said magnetic layer and partially magnetizing said layer in the opposite direction;
- and
- a second read head located proximate to said second record head, said second read head detecting a phase and magnitude of a remanent magnetization remaining in said magnetic layer after passing said second record head.
A magnetic head array for detecting magnetic hysteresis properties of a magnetic layer, said array comprising:
- a first record head producing a D.C. magnetic field in the magnetic layer, said magnetic field being selected to saturate said magnetic layer in a first direction;
- a second record head located proximate said first record head, said second record head producing a magnetic field in said layer which is opposite in direction to the magnetic field produced by said first magnetic record head, said magnetic field produced by said second record head demagnetizing said magnetic layer and partially magnetizing said layer in the opposite direction;
- wherein both said first and said second record heads are adapted to simultaneously detect a phase and a magnitude of said magnetization on said magnetic layer.
A method for measuring magnetic hysteresis properties of a magnetic material layer, said method comprising the steps of:
- saturating the magnetic material layer in a first direction with a saturation magnetic field;
- measuring a saturation remanence of the layer after removal of the saturation magnetic field;
- applying a non-saturation magnetic field having a predetermined value and a direction opposite to said saturation magnetic field;
- and
- measuring a magnitude and polarity of a non-saturation remanence of the magnetic layer after removal of the non-saturation magnetic field.
Dependencies are inferred from the claim text.