Abstract:
A tag with features to enable its authenticity to be determined includes a hidden code intermixed with a visible pattern such that the hidden code is not readily detectable under ambient light condition, without the use of a specially designed reader. In one embodiment the tag is formed with a first layer containing a hidden code, formed of reflective elements, which overlies a second layer which is designed to absorb light having a predetermined wavelength (e.g., IR light). The hidden code can be detected by projecting a light source having the predetermined wavelength (e.g., an IR source) at a predetermined angle on the tag and using a sensor to sense the reflection from the tag.

Description:
[0001]    This invention claims priority from provisional application Ser. No. 60/800,537 filed May 15, 2006 for SECURE PRODUCT AUTHENTICATION TAGS whose contents are incorporated herein by reference. 
     
     BACKGROUND 
       [0002]    A problem exists in that many items are being counterfeited. The items being counterfeited include a wide range of documents of all types as well as products and goods (e.g., currency, pharmaceuticals, and numerous brand name goods) to which counterfeited documents are appended. The counterfeited products and goods may bear tags and like identification documents, which counterfeiters append to the goods and products, falsely identifying them as the goods and products of bona fide manufacturers and distributors. Counterfeiters cause financial losses to the bona fide manufacturers and distributors by palming off their counterfeit products for the bona fide products. In addition, for example, in the case of pharmaceuticals, counterfeit products may cause harm to persons by providing an incorrect dosage or an incorrect medication. Also, the counterfeit product may have been “cut” thereby leading to an incorrect dosage. It is therefore desirable to have a means to easily detect the authenticity and provenance of products. 
         [0003]    The term “tag” or ‘“instrument” as used herein and in the appended claims is intended to include any stand alone card and/or document, as well as any tag, instrument, card or document intended to be appended or affixed to, or accompanying, goods and products. 
       SUMMARY OF THE INVENTION 
       [0004]    This invention includes apparatus and methods for generating a visibly complex pattern on an identification tag, where the complex pattern includes “coded” information which is not readily detectable by the naked eye. That is, covert information is hidden within overtly visible information. 
         [0005]    In accordance with the invention, a hidden code is intermixed with a visible pattern such that the hidden code is not readily detectable under ambient light condition, without the use of a specially designed reader. 
         [0006]    In one embodiment of the invention, a tag is formed with a first layer containing a hidden code which overlies a second layer which is designed to absorb light having a predetermined wavelength (e.g., IR light). The hidden code can be detected by projecting a light source having the predetermined wavelength (e.g., an IR source) at a predetermined angle on the tag and sensing the reflection from the tag. 
         [0007]    In accordance with an aspect of the invention, the hidden code includes elements formed of holographic style mirrors of triangular shape distributed along and/or within a designated area. The hidden code elements have sloped surfaces designed to reflect and send back the light incident on the elements in a specified direction towards a sensor. A reader for sensing and detecting the “hidden code” includes a light source designed to project light of a specified wavelength at a predetermined angle onto the distributed triangular shaped elements such that the reflected light from the elements is captured by a sensor programmed to detect the presence of a valid code. 
         [0008]    In an embodiment of the invention, a uniform light source of predetermined length is used to project light across the full length of the coded elements and their triangularly shaped elements. The light incident on the surfaces of the different triangular elements strikes them at different angles. However, the reflected light from the elements are captured by an optical sensor which is of appropriate size and appropriately positioned. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    In the accompanying drawings like reference characters denote like components; and 
           [0010]      FIG. 1  is a top view of a security tag formed and encoded in accordance with the invention when viewed under typical ambient light condition; 
           [0011]      FIG. 2  is a cross sectional diagram of a tag of the type shown in  FIG. 1 , embodying the invention; 
           [0012]      FIG. 3  is another top view of the tag of  FIG. 1  illuminated by an infrared (IR) source; 
           [0013]      FIG. 4  is a cross sectional diagram of the tag of  FIG. 1  illuminated by a reader which includes a light source and sensor to detect a hidden code, in accordance with the invention; 
           [0014]      FIG. 5  is a drawing illustrating the reflectance characteristics of a “security” pattern formed in accordance with invention in response to IR illumination; 
           [0015]      FIGS. 6A ,  6 B,  6 C are drawings showing different aspects of a pattern embodying the invention; 
           [0016]      FIG. 7  is an illustrative drawing of a light source projecting light onto the surface of a tag embodying the invention; 
           [0017]      FIG. 7A  is an illustrative drawing showing the formation of the coded information for use in practicing the invention; 
           [0018]      FIG. 8  is an illustrative drawing showing the role of an absorbing layer for absorbing light of a specified wavelength incident on a tag; and 
           [0019]      FIG. 9  is an illustrative drawing of light incident on a tag in which a highly reflective layer is formed below a layer which includes coded information. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0020]    Referring to  FIG. 1 , there is shown a top view of a tag (card or instrument)  10  embodying the invention. A complex pattern which includes coded information is formed within the top layer (see  35  in  FIG. 2 ) of the tag. The top layer  35  may be formed of a material having a high refraction index (HRI) or any other suitable material as discussed below. When viewed under ambient light condition (e.g., fluorescent light), a pattern is seen due to the multiple angle reflections (see  FIGS. 1 ,  6 A and  6 B). However, the coded information present within a region of interest  20  is not (readily) identifiable apart from the complex pattern. 
         [0021]    As shown in  FIG. 2 , in accordance with one embodiment of the invention, the tag  10  includes a base layer (substrate)  31 , over which there is formed an infrared (IR) absorbing layer  33 , over which is formed a layer of material  35  which may be of a high refractive index (HRI) material. Layer  35  may be formed of HRI material or any other material having similar optical characteristics as the HRI material. A complex pattern is formed so as to extend over a large portion of the surface area of the tag  10 . In  FIG. 2 , the coded portion is formed within the HRI layer  35  and extends within a region of interest  20 . Under ambient light condition, light is reflected from the surface displaying a generally complex pattern and the coded information can not be readily distinguished from the general complex pattern. 
         [0022]    In accordance with one aspect of the invention, when used in combination with the appropriate tag build-up, the tag with the HRI (High Refractive Index material) will only function in a manner that is machine readable when excited by infrared illumination at the appropriate angle. That is, the coded information formed on the tag, as part of a complex pattern, can only be sensed when illuminated by an IR source at a preselected angle, as shown in  FIGS. 3 and 4  and  FIGS. 7-9 . 
         [0023]      FIG. 3  is a top view of the tag of  FIG. 1  being illuminated with IR illumination at a prescribed angle. For this light condition, the code pattern which would be sensed by a sensor/detector  64  focused on the designated area is shown in  FIG. 6B .  FIG. 4  shows a cross section of the tag  10  with coded section  20  illuminated by a reader/sensor  60 . Reader  60  includes a light source  62  and an image sensor  64 ; which may be a linear or an area sensor. A focusing lens (not shown) may be formed as part of the detector  64  to capture the light reflected from the designated area  20 . Light source  62  is used to illuminate the coded information and sensor  64  senses the reflection from the illuminated object. In  FIGS. 3 and 4 , the light source  62  is an IR light source which is selected to have a wave length which will be absorbed by the intermediate layer  33  which is designed to absorb IR radiation. The light  70  from light source  62  is also projected at a prescribed angle (alpha) to ensure that the reflection will be correctly sensed by sensor  64 .  FIG. 5 , illustrates the reflectance characteristic of the coded information to the IR illumination. 
         [0024]    As shown in  FIGS. 3 and 4 , due to the absorbency of the IR layer  33 , IR light  70  from an IR source  62  incident on the tag at an angle alpha will result in the “hidden” pattern within region  20  to be reflected back towards the reader  60  (see  FIG. 4 ). The “overt” design pattern will be faintly visible, while the coded information will be sensed and decoded by the reader  60 . 
         [0025]    Thus, under normal lighting conditions such as a fluorescent lighting the illumination impinging on the tag is actually coming from many directions (i.e. diffuse) and the tag will appear to have characteristics similar to that shown in  FIG. 6B . The HRI artwork in the tag has a rainbow like feature that will reflect different wavelengths of light energy contained within the white light at different angles. This will yield a colorful reflectance pattern with no apparent directionality. However when the tag is illuminated from a single specific angle and a single specific wavelength then the reflectance characteristics will yield an image that will look like that shown in  FIG. 6C . The image shown in  FIG. 6C  can then be easily detected by a CMOS or CCD linear or area image sensor. The output signals from the imager  64  can then feed a microcontroller  80  that will interrogate the pattern and determine if the optical characteristics of the tag is valid or a counterfeit. 
       Tag Construction 
       [0026]    The cross-section of a tag embodying the invention is shown in  FIGS. 2 and 4 . The top layer  35  may be a HRI material that has specific optical characteristics and patterns that will be used in the detection scheme. Layer  35  may also be any material that has similar reflectance characteristics to those of the HRI material. The backing of the HRI layer is an adhesive layer  33  that can have additional optical characteristics. For example, the material comprising layer  33  may be designed to absorb most of the IR illumination. This will produce the necessary optical contrast that is required for detection of the HRI pattern in layer  35 . Layer  33  may be an absorbing layer and also an adhesive layer or an independent layer which includes the IR absorbing characteristics. The base layer  31  may be a tag base or a plastic or paper carrier. The base layer may also contain an adhesive that can be used to apply the tag to a specific product. 
         [0027]    In some embodiments the base layer  31  is not needed. Layer  33  may be an adhesive layer having desired optical characteristics and be capable of adhering to layer  35  formed above it and to any selected surface below it. Thus, the tag base  31  may not be needed where it is desired to form a very thin tag, which can be appended to any suitable surface. 
         [0028]    In  FIGS. 1-4  the tag  10  is illuminated by a source of IR illumination. For this embodiment, at, or about, the time the tag is made and finalized, the reflective optical pattern sensed by a sensor (e.g., sensor  64 ) in a reader (e.g., reader  60 ) in response to the IR illumination can be stored either on/in an external database for verification or locally, on/or within the tag, or on/in an RFID (radio frequency identification) chip, or a barcode that is co-located as part of the tag, or within electronic storage in microcontroller  80 . Subsequently, the RFID data and/or the barcode or database information may be compared with subsequently scanned optical information via a comparator such as microcontroller  80 . The verification of the optical characteristics by the verification data is used (e.g., by means of microcontroller  80 ) as a self checking system validating the authenticity of the tag. 
         [0029]    Thus, in accordance with the invention, the “hidden”, covert, information is “mixed” in with an overt optical pattern and characteristics formed within a first layer shown as the top HRI layer on the tag. The pattern formed on the top of the tag looks as if it is a pseudo random geometric pattern but portions of the “pseudo-random” pattern are in fact specifically coded for detection and validation. 
         [0030]    The tag construction may include an adhesive and or second layer that is transparent to the naked eye but in fact includes optical characteristics and properties that can absorb any IR illumination. The material in the second layer that yields the IR absorption characteristics can be part of the adhesive between the top layer (e.g.,  35 ) and the base layer (e.g.,  31 ). 
         [0031]    An aspect of the invention relating to the construction of the tag with a hidden code formed within a region  20  and for detecting the hidden code may be best understood with reference to  FIGS. 7 and 7A . The hidden code comprising, for example, reflective (or holographic) elements e 1 , e 2 , e 3 , e 4 , e 5  may be formed within a region  20  (as shown in  FIGS. 1-4 ). As shown in  FIG. 7A , each reflective (or holographic) element (e.g., e 1 , e 2 , e 3 ) is comprised of a number of triangular elements (e.g., reflective element e 1  includes triangular elements e 11 , e 12 , reflective element e 2  includes five triangular elements e 21 -e 25  and reflective element e 3  includes triangles e 31 , e 32 ). The number of triangular elements per reflective (holographic style) element determines the thickness (or width, or intensity) of the corresponding reflective (holographic) element when sensed by a sensor (or seen by a viewer). The triangular elements are shown to be formed with a constant angle relative to the horizontal. Note that the “coded information” or “hidden code” is shown to include triangular elements which function as mirrors with sloping surfaces presenting angles (due to the slope) for reflecting light impinging on the sloping surfaces. 
         [0032]    To detect the coded information, a uniform linear light source  62  is used to projects light onto and across (and along) the triangular elements. Light (e.g., L 1 , L 5 ) impinging on the triangular elements (e.g., e 1 , e 5 ) is reflected back and sensed (captured) by sensor  64 . Light (e.g., Lp) impinging on the space (e.g., p 1 ) between triangular elements is either absorbed by the underlying material or reflected (e.g., Lpa) at such an angle that it is not captured or sensed by the sensor  64 . The uniform linear light source must thus have sufficient length (i.e., “d” as shown in  FIG. 7 ) to produce light which will impinge on all the elements (e.g., e 1 , e 5 ) of the hidden code at such angles that the reflection from each element is captured by the sensor  64 . Evidently, this also requires that the optical sensor  64  be of sufficient size, or area, to capture the light reflected from the reflective (holographic) elements. 
         [0033]      FIG. 8  illustrates that the tag  10  is formed such that below layer  35 , which includes the code information, there is formed a layer  33  which absorbs illumination of specific wavelength(s). A light source  62   a  having these specific wavelength(s) will project light impinging on and along the coded area. Light (e.g., L 1 , L 5 ) impinging on reflective or holographic elements is reflected back (e.g., L 1   a , L 5   a ) and captured by the sensor  64 . Light impinging on the space p 1 , in which there is/are no triangular elements is absorbed by the layer  33 . Thus, the tag and the light source are designed as part of a system to produce tags with characteristics which can only be effectively sensed by a suitable light source and sensor. 
         [0034]      FIG. 9  illustrates that the tag  10  may be formed of a layer  35  which includes coded information overlying a highly reflective metallized layer  330 . The light (e.g., L 1 , L 5 ) impinging on the coded elements is reflected (e.g., L 1   a , L 5   a ) towards the sensor  64 . The light (e.g., Lp)) hitting the surface where there is/are no coded elements (e.g., p 1 ) is reflected at an acute angle and is not captured by the optical sensor  64  which is appropriately positioned. 
         [0035]    The reader  60  of the invention thus includes a light source  62  and an optical sensor  64  which are tailored to illuminate selected tags and to reliably sense the coded information to determine whether the tag is authentic. The reader  60  may be a hand held device including a shield for selectively blocking ambient light, or a fixed mount device or part of any suitable reading enclosure.