Image analysis – Image sensing – Magnetic
Reexamination Certificate
1999-01-14
2001-09-11
Patel, Jayanti K. (Department: 2721)
Image analysis
Image sensing
Magnetic
C340S572600, C382S135000
Reexamination Certificate
active
06289141
ABSTRACT:
BACKGROUND OF THE INVENTION
Many techniques are available to authenticate a product, that is to verify its legitimacy as compared to copies. The list of technologies applied to this problem is very long and includes many kinds of complex printing with overt or covert information, holograms, embedded materials and chemicals in trace amounts, magnetic additives, etc. All employ a specially manufactured label or tag that is attached permanently to the true product. Verification of the authenticity of the label or tag also verifies the authenticity of the product. The advantages of these techniques are that they provide unique, difficult to copy ways of differentiating real products from counterfeit ones.
Unfortunately, current authentication technologies are not without weaknesses. Usually, if cost is not a consideration, they can be copied to some degree. In addition, since many techniques rely only on visual inspection for verification, human error becomes a significant consideration. Finally, some methods rely on specialized equipment for verification and may be too expensive, cumbersome or slow to be effective in many situations. Currently, standardization is neither possible nor likely.
What is needed in an authentication technology is one that: 1) gives authentication information that can be detected swiftly an clearly in a quantitative manner; 2) is very difficult to copy; 3) can migrate easily to more sophisticated, more difficult to defeat levels of complexity; and 4) is compatible with existing methods of marking or labelling goods.
A technology that partially succeeds in meeting the above criteria is the “magentics” technology. It operates by searching for the presence of ferromagnetic material attached to the product that is to be authenticated. It analyzes the magnetic signature of the ferromagnetic material, focusing on specific and unique magnetic properties. A number of patents have been issued in this area for applications in authentication and other functions. Unfortunately, this approach has a major weakness in that uncontrollable variations can occur in the results of this measurement due to geometrical factors, thus affecting its accuracy and making it potentially unreliable.
A proper authentication system has many uses. It will provide a method of verifying the authenticity of a product in the field. It is useful in establishing a distinction between real and counterfeit products for legal purposes. When coupled to an actuator, it can be used to control document duplication and other information copying related processes such as photocopying, faxing and data transmission. For example, the unauthorized photocopying of a document may be blocked by adding an authentication reader to a photocopier.
SUMMARY OF THE INVENTION
This invention overcomes many of the problems listed previously and meets the criteria put forward for an improved authentication system. Like all currently available solutions, it depends upon the addition of a unique material or marker to an article in order to confirm its authenticity. However, it is superior to competing technologies in that it gives quantifiable, objective results and offers a means of simply and easily authenticating the marker. It does this by combining a feedback control system with a “magnetics” measuring system, resulting in precise determination of the characteristics of the marker. The usefulness of this invention is further enhanced by the fact that it is applicable to a wide variety of products, such as currency, documents, clothing, videos, CD's, toys, perfumes, etc., Finally, it is easily adapted to the problem of controlling the unauthorized duplication of documents and magnetic storage media.
The physical basis for this invention is described briefly below. When a magnetic material is introduced into a magnetic field, the magnetic flux will concentrate preferentially in the magnetic material because of its higher permeability relative to air. The degree of concentration of the flux is dependent upon the permeability of the magnetic material and its geometry.
When this ferromagnetic material is introduced into a time varying magnetic field, a more complex process occurs. Because the permeability of the magnetic material is not a constant, but changes as the external field changes, the spatial distribution of the flux changes in a unique way. In fact, the characteristics of the magnetic material. This change can be measured and is the basis for the hysteresis curve for magnetic materials.
The change in the spatial distribution of the flux is greater for larger values of permeability than for smaller values. In addition, it is also governed by the characteristics of the time varying external field, the shape and size of the magnetic material itself and the orientation of this material with respect to the external field. By controlling all other variables and using well known techniques to measure the time change in the spatial flux distribution, it is possible to uniquely recognize the magnetic material causing the change.
The invention based upon this physical principle has two essential components, a marker and a reader. The marker is optimally designed to have high permeability and low coercivity, so that it can interact strongly with the time varying electromagnetic search field and create an easily detectable and predictable change in the spatial flux distribution. The reader emits the electromagnetic search field that creates the flux which is then changed in some manner when the marker is introduced. It also measures and analyzes the resultant change in flux, using standard signal analysis techniques. The result is a set of parameters, that are then compared to a reference set of values stored in the detecting electronics. If there is a match to within the required degree, the article is genuine. The set of parameters used as the defining set is typically a subset of all the available parameters and is chosen to optimize the measurement process. It may vary depending upon the properties of the magnetic materials and the measurement techniques used.
In practice, there is a change in some of the parameters that are used to characterize the magnetic material due to the orientation and position of that material in the magnetic field. This variation will occur even though there is no change to the field or the magnetic properties of the magnetic material itself and it will affect the usefulness of the measurement in an authentication function. This problem is overcome in this invention by incorporating a feedback control system into the reader to maintain a constant reading environment (i.e. to stabilize the measurement).
A magnetic material will create a signal consistent with its magnetic properties. Given that the geometry of the measurement system and the characteristics of the stimulating field (such as the frequency and shape of the waveform and the strength of the field that is created) can be kept constant, the signal will uniquely represent the magnetic properties of the material causing it.
The magnetic properties of a material are a function of the component chemical elements, the method of manufacture, the various additional processes such as heat treatment that can be used on the magnetic material and its magnetic history. Therefore, magnetic properties can be controlled both at the time of manufacture and after.
The magnetic properties of materials are given by the B-H or hysteresis curve. From this curve, parameters such as permeability at different points of the curve, saturation and coercivity are taken. The hysteresis curve is also defined for a given frequency of stimulus or H field and will vary in shape as the frequency is changed. Consequently, these parameters take different values as the frequency changes. This leads to the availability of many possible parameters which can be used to distinguish between materials with different magnetic properties and to an almost unlimited number of materials with distinct magnetic properties. It can be reasoned that it would be difficult to fin
Patel Jayanti K.
Shoemaker and Mattare LTD
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