Device and method for determining the authenticity of documents
First Claim
1. A method of determining the authenticity of a document having a known permittivity, said method comprising the steps of:
- sensing complex electric permittivity of the document based on frequency dependent dielectric properties of the document using a plurality of interdigitated electrodes arranged substantially in a plane and electrically excited by a sensing circuit, wherein the document is positioned against the interdigitated electrodes;
providing an output corresponding to the sensed permittivity; and
processing the output to provide an indication regarding whether or not the document is genuine.
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Abstract
There is a large difference in frequency dependent, complex electrical permittivity between genuine and counterfeit documents, including paper currency. Genuine bills have a substantially different complex permittivity which is distinct from the permittivity of counterfeit bills. The invention broadly measures the complex permittivity, ε, of the ‘paper’ bills to determine if the bill(s) is genuine or counterfeit. In one aspect, the present invention comprises a device and method for determining the genuineness of a document by measuring the complex permittivity based on the frequency dependent dielectric properties of the document. The complex electric permittivity of a dielectric material is typically read by measuring complex impedance using a capacitor to sense material properties. The document may include an enhanced region comprising an additive that establishes a known permittivity in the enhanced region. For example, the enhanced region may be established by using a “smart ink” that is applied to the document, or a dopant that may be built into the document itself. The “smart ink” or dopant may include carbon nanotubes, barium titanate, barium strontrium, or in general ferroelectric materials having a relatively high permittivity and a ferroelectric transition point that is above room temperature (e.g., lithium niobate, rochelle salt, sodium niobate, lithium tantalate). To determine the authenticity of the document, the permittivity of the enhanced region is measured. Advantageously, providing the enhanced region changes the local properties of the document to prevent document counterfeiting.
37 Citations
30 Claims
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1. A method of determining the authenticity of a document having a known permittivity, said method comprising the steps of:
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sensing complex electric permittivity of the document based on frequency dependent dielectric properties of the document using a plurality of interdigitated electrodes arranged substantially in a plane and electrically excited by a sensing circuit, wherein the document is positioned against the interdigitated electrodes;
providing an output corresponding to the sensed permittivity; and
processing the output to provide an indication regarding whether or not the document is genuine. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
outputting a frequency corresponding to a measured capacitance; and
sensing if the frequency is within a predetermined range which corresponds to a genuine document.
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5. The method of claim 1, wherein said step of sensing complex permittivity of the document includes sensing the complex permittivity of an enhanced region of the document, wherein the enhanced region includes an additive that establishes the known permittivity in the enhanced region.
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6. The method of claim 5, wherein the additive is included in ink which is deposited onto the document to establish the enhanced region.
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7. The method of claim 5, wherein the additive is integral with fibers of the document to establish the enhanced region.
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8. The method of claim 5, wherein said additive comprises a high dielectric material selected from the group of carbon nanotubes, barium titanate, barium strontrium, and ferroelectric materials having a relatively high permittivity and a transition impedance that is above room temperature such as lithium niobate, rochelle salt, sodium niobate, lithium tantalate.
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9. The method of claim 5, wherein the additive includes micro transponders.
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10. The method of claim 5, wherein the enhanced region is a bar code.
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11. A device for determining the genuineness of a document having a known permittivity, said device comprising:
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means for measuring permittivity of the document based on frequency dependent dielectric properties of the document, comprising a plurality of interdigitated electrodes arranged substantially in a plane and electrically excited by a sensing circuit, wherein the document is positioned against said interdigitated electrodes and said electrodes measure the permittivity across a substantial portion of the document;
means for providing an output corresponding to the measured permittivity; and
means for processing the output to provide an indication regarding whether or not the document is genuine. - View Dependent Claims (12, 13, 14, 15, 16, 17)
a plurality of electrode sensors adapted to engage the document and to form with the document a capacitor.
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15. The device of claim 14 wherein said means for measuring comprises:
an oscillator circuit whose resonant frequency depends upon the value of the capacitor formed by the electrode-document combination.
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16. The device of claim 11 wherein said means for processing the output comprises a tone decoder.
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17. The device of claim 16 wherein the tone decoder is a phase locked loop circuit.
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18. A device for determining the genuineness of a document having a known permittivity, said device comprising:
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means for measuring permittivity of the document based on frequency dependent dielectric properties of the document, comprising a plurality of coated electrodes arranged on opposite sides of the document and electrically excited by a sensing circuit; and
means for providing an output corresponding to the measured permittivity and for processing the output to provide an indication regarding whether or not the document is genuine. - View Dependent Claims (19, 20, 21, 22, 23, 24, 25)
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26. A method of authenticating an object, comprising the steps of:
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determining the complex permittivity of the object; and
comparing the measured complex permittivity of the object against a known standard to determine the authenticity of the object, wherein said step of determining the complex permittivity of the object includes sensing the complex permittivity of an enhanced region of the object, wherein the enhanced region includes an additive selected from the group comprising carbon nanotubes, barium titanate, barium strontrium, microtransponders and ferroelectric materials having a relatively high permittivity and a ferroelectric transition point that is above room temperature such as lithium niobate, rochelle salt, sodium niobate, lithium tantalate, such that the additive establishes a known permittivity in the enhanced region. - View Dependent Claims (27, 28, 29, 30)
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Specification