Patent Description:
Counterfeiting is a growing concern and, as a result, secure instruments such as banknotes typically have three levels of authentication. Level I authentication is for public uses and is typically in the form of an optical effect, such as optically variable ink or security threads with optical characteristics that are relatively unique and difficult to duplicate. These Level I authentication features include holographic threads and lenticular lens array security threads. Paper banknotes have included Level I authentication features in the form of watermarks.

Similar to Level I authentication features, Level II authentication features are typically known to the public and commercial banks, and include features such as magnetics and fluorescent and phosphorescent inks, which can be read by simple sensors commonly used in ATMs and bill acceptors.

Level III security features are machine readable features and are more sophisticated than Level II authentication features. Level III security features are typically not known to the public and commercial banks and are used to protect against threats from state-sponsored counterfeiters and other well-funded organizations. The covert Level III authentication features are typically either in the form of inks or other features embedded in the substrate of the banknotes.

Over the last two decades, polymer banknotes have gradually been gaining market share in the banknote industry, with over thirty countries using polymer substrates including materials such as Biaxially Oriented Poly-Propylene (BOPP). The use of polymer substrates has been primarily restricted to lower denominations, as most of the Level III security features that have been employed within paper banknote substrates are not available or suitable for use with polymer banknotes.

Document <CIT> discloses systems and methods for document and product authentication using a variety of absorption and emission signatures. Emission signatures in the form of florescent or phosphorescent coatings, inks and substrates are being used for authentication and protection of items such as documents, currency, and secondary packaging for tobacco, luxury goods and pharmaceuticals. Spectrally overlapping absorption and emission materials are being combined to provide a unique spectral fingerprint detectable by a scanner.

The present invention concerns a new Level III security feature in the form of a machine readable technology for use with polymer banknotes.

In general, in one aspect, the invention features a method for authenticating an item, including irradiating the item, the item including a polymer substrate including a polymer transmit material and a doping material and configured to transmit a radiation spectrum having a spectral signature in response to the irradiating, the doping material capable of absorbing and scattering radiation at a specific wavelength to generate the spectral signature, detecting the spectral signature, and determining a code associated with the spectral signature.

Implementations of the invention may include one or more of the following features. The method may include comparing the determined code to a reference code or providing an indication of authenticity if the determined code matches the reference code. The spectral signature may be an absorption and scattering pattern in the radiation spectrum. The spectrum may include visible light or non-visible electromagnetic radiation.

The irradiating may include providing an incident spectrum. The polymer material may be biaxially oriented poly-propylene. The doping material may be capable of absorbing and scattering radiation at a plurality of specific wavelengths to generate the spectral signature. The absorbed and scattered radiation at the plurality of specific wavelengths may have different intensities at each of the plurality of specific wavelengths.

The item may be currency. The method may include covering the polymer substrate with an opacity layer.

In general, in another aspect, the invention features a system for authenticating an item, including a radiation source for irradiating the item, the item including a polymer substrate including a polymer material and a doping material and configured to emit a radiation spectrum having a spectral signature in response to the irradiating, the doping material capable of absorbing and scattering radiation at a specific wavelength to generate the spectral signature, and a sensor configured to detect the spectral signature.

Implementations of the invention may include one or more of the following features. The system may include a computing device for determining a code based on the spectral signature. The computing device may be configured to compare the determined code to a reference code and to determine whether the item is authentic based on the comparison of the determined code to the reference code.

The spectral signature may be an absorption or scattering pattern in the radiation spectrum. The doping material may be capable of absorbing or scattering radiation at a plurality of specific wavelengths to generate the spectral signature, the absorbed or scattered radiation having different intensities at each of the plurality of specific wavelengths, and the sensor configured to detect the intensities at each of the plurality of specific wavelengths in the spectral signature.

The sensor may include an imaging device of a smartphone or a tablet. The system may include a radiation source for providing an incident spectrum.

The present invention provides for apparatus and methods for coding polymer substrates with the addition of doping materials, and authentication systems and methods using the coded polymer substrates. The coded polymer substrates may be used, e.g., for authenticating secure items, instruments or documents, such as banknotes or currency.

A polymer substrate employed in the present invention may be a BOPP layer. Such a BOPP substrate, as used in banknotes or currency, may be approximately <NUM> microns in thickness. In one embodiment, the polymer substrate may include a clear area or window free from opacity, as is often the case in higher denomination polymer banknotes. The opacity layer of the banknote, either alone or in combination with the area free from opacity, may function as the analog of paper banknote watermark for polymer banknotes.

Doping materials may be nanometer and micrometer materials added to the BOPP material. The doping materials may be added to the BOPP material during extrusion of the polymer layer. The doping materials are selected to be well matched to the index of refraction of the BOPP material and to maintain the clarity and transparency of the BOPP material.

The doping materials may be inorganics, organics, semiconductor and nanostructures exhibiting exciton, phonon polariton and plasmonic modes, and particularly those that can survive the extrusion temperatures of the BOPP material or other selected polymer material. The doping materials may be added to or loaded in the BOPP material at <NUM>-<NUM>% loadings by weight. Most significantly, each doping material exhibits a unique absorptive or scattering property or signature in the spectrum of incident radiation transmitted through the BOPP material in the region from the far infrared to the long ultraviolet. In particular, the doping materials selectively absorb and/or scatter incident radiation at specific wavelengths. By combining specific absorption and/or scattering features of various doping materials, codes for authentication of the banknotes are created in the form of patterned spectra with notches i.e., absorption or scattering patterns.

<FIG> show spectra for a band of incident radiation in the near infrared portion of the electromagnetic spectrum transmitted through a clear <NUM> micron polymer layer with varying types and levels of doping materials. The intensities of radiation detected after transmission of incident radiation through the polymer layer vary from the otherwise substantially uniform intensity of the incident radiation over the band of wavelengths due to the presence of doping materials. The doping materials are selected to absorb and/or scatter radiation at predetermined wavelengths to create the notched and otherwise non-uniform detected spectral patterns.

Experiments have demonstrated the use of up to ten unique codes embedded in a spectrum of radiation transmitted through a BOPP material that further maintains excellent clarity in regions of the BOPP material lacking an opacity layer and is indistinguishable from un-doped BOPP material. Using shape and Fano resonance effects, metallic and semiconductor nanostructure resonances of doping materials can be tuned and manipulated to create a large array of codes. These codes may be specific to certain institutions, such as Central Banks. The codes may also be used to authenticate banknotes and/or determine the denominations of banknotes on high speed sorting machines, such as those manufactured by Geiseke and Devrient and De La Rue International.

Exemplary embodiments of the present invention are generally directed to devices, apparatus, systems, and methods for authentication using coded polymer substrates. Specifically, exemplary embodiments of the present invention use detecting/sensing mechanisms that may be used to authenticate items including a coded polymer substrate. Although the exemplary embodiments of the present invention are primarily described with respect to authentication and/or preventing counterfeiting, it is not limited thereto, and it should be noted that the exemplary coded polymer substrates may be used to encode other types of information for other applications. Further, the exemplary embodiments of the present invention may be used in conjunction with other authentication measures, e.g., holograms, watermarks, and magnetic encoding.

<FIG> shows an exemplary system <NUM> in accordance with embodiments of the present invention. As shown in <FIG>, system <NUM> may include a radiation/excitation source <NUM>, a sensor <NUM>, and a coded polymer substrate <NUM>. Radiation/excitation source <NUM> may be any source supplying radiation <NUM>, such as, e.g., visible light, ultraviolet radiation, radio waves, or microwaves, which is to be absorbed by the coded polymer substrate. The coded polymer substrate <NUM> may re-emit radiation <NUM> in the same wavelength range or emit radiation <NUM> in a different wavelength range.

Sensor <NUM> may include any detecting, sensing, imaging, or scanning device that is able to receive, image and/or measure the spectrum of the radiation emitted by the coded polymer substrate <NUM>, such as a photometer or a digital camera.

According to certain exemplary embodiments of the present invention, radiation/excitation source <NUM> may include the flash of a digital camera, and sensor <NUM> may include the optical components and sensors of the digital camera. In one exemplary embodiment, the radiation/excitation source <NUM> may include the light source of a smartphone or tablet camera, e.g., Apple iPhone, Apple iPad, Samsung Galaxy or other Android devices, and sensor <NUM> may include the camera of the smartphone or tablet.

Coded polymer substrate <NUM> may be included in labels and may be attached or affixed to any product or item, e.g., tax stamps, apparel, currency, or footwear, for which authentication may be desirable.

<FIG> shows an exemplary system <NUM> that may be employed to authenticate an item using the coded polymer substrate described herein. For example, system <NUM> includes a computing device <NUM>, which may include radiation/excitation source <NUM> and sensor <NUM>. Computing device <NUM> may be any computing device that incorporates a radiation/excitation source <NUM> and sensor <NUM>, such as a smartphone, a tablet, or a personal data assistant (PDA). Alternatively, radiation/excitation source <NUM> and sensor <NUM> may be stand-alone devices that operate independent of a computing device. As described herein, the radiation/excitation source <NUM> may irradiate a coded polymer substrate, and sensor <NUM> may measure the radiation emitted by the coded polymer substrate, including the spectral signature. The computing device <NUM> determines a code corresponding to the measured spectral signature of the radiation emitted by the coded polymer substrate. The processing of the measured spectral signature to determine the code may be performed by a remote computing device. Subsequently, the code or the measured spectral signature may be compared to a database of reference codes or spectral signatures. The database of reference codes may be stored locally on the scanning, imaging, or sensing device or remotely on a separate computing device.

As shown in <FIG>, to complete the authentication, the computing device <NUM> may compare the code or the measured spectral intensities to the reference codes or spectral signature stored in a database <NUM>. Although <FIG> illustrates this comparison being performed via a network <NUM> to a remote database <NUM>, other embodiments contemplate database <NUM> being local to computing device <NUM>.

Further, in some embodiments, the item being authenticated may include an identifying label, such as, e.g., a barcode, a QR code, or a magnetic code, to enable correlation of the code or the measured spectra to the item being authenticated. In a particular embodiment where computing device <NUM> is a smartphone or tablet, the transmission via the network <NUM> may be performed over a cellular data connection or a Wi-Fi connection. Alternatively, this can be performed with a wired connection or any other wired or wireless data transport mechanism.

In certain embodiments of the present invention where a computing device, such as a smartphone or tablet, is utilized for authenticating an item, a software application may be used to simplify the authentication process. <FIG> shows a smartphone with an exemplary screen shot of a software application that may be utilized for authenticating an item. The exemplary application may be configured to be executed on any mobile platform, such as Apple's iOS or Google's Android mobile operating system. When the application is run, the software application may provide instructions to a user on properly irradiating or exciting the coded polymer substrate and scanning or imaging the spectrum emitted from the coded polymer substrate. Once the irradiating and scanning of the polymer substrate is complete, the application may facilitate comparison of the measured spectral signature and/or the measured code with a database that stores certain reference codes or spectral signatures to authenticate the item. Further, the application may provide a message or other indicator informing the user of the result of the authentication. For example, the application may provide a text, graphical, or other visual indicator on the screen of the smartphone showing the results of the authentication. Alternatively, the application may provide audible and/or tactile indicators conveying the results of the authentication.

Claim 1:
A method for authenticating an item (<NUM>) which includes
a polymer substrate comprising a polymer material and a doping material,
the polymer substrate having a clear area, and
the polymer material and doping material being configured to transmit radiation through the clear area of the polymer substrate,
and the doping material capable of absorbing and scattering radiation of at least one specific wavelength to generate a spectral signature including a notched pattern in a spectral band of wavelengths of the transmitted radiation; the method comprising:
irradiating the item with incident radiation wherein a spectral band of wavelengths including the at least one specific wavelength absorbed and scattered by the doping material, the polymer substrate absorbing and scattering radiation of the incident radiation to generate the spectral signature and transmitting the radiation having the generated spectral signature through the clear area of the polymer substrate;
detecting the spectral signature in said spectral band of wavelengths of the transmitted radiation after the radiation is transmitted through the clear area of the polymer substrate; and
determining a code associated with the spectral signature and using the code for authentication.