Abstract:
A method for authenticating an object that includes providing a label ( 12 ) with invisible indicia ( 14 ) printed with optically active material on a reflective substrate; providing a device that has a digital camera ( 18 ) having a light source ( 20 ), an image sensor ( 22 ), a first polarizing filter ( 24 ) having a first orientation, and a second polarizing filter ( 26 ) having a second orientation; illuminating the label with the light from the light source through the first polarizing filter; forming an image with the image sensor using reflected light from the label wherein the reflected light passes through the second polarizing filter prior to reaching the sensor; wherein the second polarizing filter makes the invisible indicia visible; and authenticating the object.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     Reference is made to commonly-assigned U.S. patent application Ser. No. 13/755,329 (now U.S. Publication No. 2014/0211071), filed Jan. 31, 2013, entitled CELL PHONE AUTHENTICATION DEVICE, by Pawlik et al.; the disclosure of which is incorporated herein. 
     FIELD OF THE INVENTION 
     This invention relates in general to authentication of objects and in particular to authentication of objects using a cell phone. 
     BACKGROUND OF THE INVENTION 
     Invisible indicia printed with an optically active material on a reflective substrate can be used as a covert security feature on products and product packaging. The product is authenticated by revealing the invisible indicia with the use of a circular polarizing filter. The circular polarizing filter is held in close proximity to the printing. The person holding the filter can then authenticate the item by visually verifying the image or human-readable text or code that is revealed as expected. While this can be an effective security feature, the authentication process has limitations. 
     When authenticating product out in the field, it is often the case that many items need to be authenticated sequentially, and the results of the authentication audit need to be transmitted to another location. It is therefore useful to be able to automate the method for recording and storing the results and to have a convenient means of transmitting the results once collected. 
     It is sometimes desirable to have an immediate response to a positive or negative authentication audit. It is therefore useful to have a system that can not only transmit the results of an authentication audit, but also then receive a response back. 
     It is also often desirable to encode a large amount of data in invisible indicia, for example an item-level serialized number. To reduce the amount of space required to print the data or to speed up reading the printed information, it can be printed in the form of a machine readable code rather than a human-readable code, for example a linear or 2-dimensional bar code. It is therefore useful to be able to quickly and conveniently decode a revealed machine-readable code to be able to quickly authenticate the item. 
     Finally, at times, it is very desirable for investigators to perform their audits in a covert manner, often without handling the item to be authenticated. It is therefore useful to be able to authenticate an item from some distance away and not to require the revealing device be in close proximity. 
     SUMMARY OF THE INVENTION 
     Briefly, according to one aspect of the present invention a method for authenticating an object that includes providing a label with invisible indicia printed with optically active material on a reflective substrate; providing a device that has a digital camera having a light source, an image sensor, a first polarizing filter having a first orientation, and a second polarizing filter having a second orientation; illuminating the label with the light from the light source through the first polarizing filter; forming an image with the image sensor using reflected light from the label wherein the reflected light passes through the second polarizing filter prior to reaching the sensor; wherein the second polarizing filter makes the invisible indicia visible; and authenticating the object. 
     In one embodiment, a cellular telephone comprises the digital camera. The first and second polarizing filters are located externally to the cellular telephone, for example in or on a case, and are in front of the flash and the digital camera, respectively. Both filters are linear polarizing filters and are oriented orthogonally to each other. Light from the flash of the digital camera is polarized as it passes through the first linear polarizing filter. When the polarized light strikes a label with invisible indicia printed with optically active materials on a reflective substrate, it will reflect off the invisible indicia with a change in the direction of the polarization. The polarized light that reflects off the background of the label will have no change to its polarization. Thus, the invisible indicia are differentiated from the background. 
     The orthogonally oriented second linear polarizing filter located over the digital camera will block the unchanged polarized light reflecting from the background making it appear dark on the image sensor of the digital camera, but the polarized light reflecting from the invisible indicia will be only partially blocked and thus will appear bright on the image sensor of the camera. The resulting image can then be analyzed, for example, decoded if it is a linear or two-dimensional bar code, or stored in the memory of the cell phone, or transmitted via the cell phone. Once invisible indicia have been decoded and transmitted via the phone, a response can be received by the phone, for example, further information about the item being authenticated. Additionally, if the investigator is an end-user consumer, the information sent back to the investigator via the phone could be promotional information or a coupon that the investigator can use in connection to the item. If the investigator is associated with the supply chain of the item, the information transmitted could initiate restocking of items or other movement of material in the distribution chain. 
     In a second embodiment, a cellular telephone is the device with the digital camera. The first and second polarizing filters are located externally to the cellular telephone, for example in or on the case, and are in front of the flash and the digital camera, respectively. Both filters are circular polarizing filters and have identical orientation to each other. The first circular polarizing filter can be created by placing a quarter wave plate after a first linear polarizer. In one example, the axis of the linear polarized filter is positioned at a 45 degree angle from the fast axis of the quarter wave plate to achieve left hand circular polarization. Light from the flash of the digital camera is circularly polarized as it passes through the first circularly polarizing filter. 
     When the polarized light strikes a label with invisible indicia printed with optically active materials on a reflective substrate, it will reflect off the invisible indicia differently than it will reflect off the background. The polarized light that reflects off the background of the label will be changed to right hand circular polarization. This right hand circular polarized light will be blocked by the second circular polarizing filter, which is oriented identically to the first filter, and will appear dark to the image sensor of the digital camera. The light reflected off the optically active invisible indicia will have its polarization direction changed, but not to right hand circular polarization. Thus, the invisible hidden indicia are differentiated from the background. The identically oriented second circular polarizing filter will only partially block the light reflected off the optically active hidden indicia and thus will appear bright on the image sensor. 
     The resulting image can then be analyzed, for example, decoded if it is a linear or two-dimensional bar code, or stored in the memory of the cell phone, or transmitted via the cell phone. Once hidden indicia have been decoded and transmitted via the phone, a response can be received by the phone, for example further information about the item being authenticated. Additionally, if the investigator is an end-user consumer, the information sent back to the investigator via the phone could be promotional information or a coupon that the investigator can use in connection to the item. If the investigator is associated with the supply chain of the item, the information transmitted could initiate restocking of items or other movement of material in the distribution chain. 
     The invention and its objects and advantages will become more apparent in the detailed description of the preferred embodiment presented below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a flow diagram of the method of the invention. 
         FIG. 2  is a schematic of an authenticating device and item to be authenticated. 
         FIG. 3  is a schematic representation of a label with invisible hidden indicia printed with optically active material on a reflective surface. 
         FIG. 4  is a schematic of an authenticating device, where the two polarizing filters are linear polarizing filters, and an item to be authenticated. 
         FIG. 5  is a schematic of an authenticating device, where the two polarizing filters are circular polarizing filters, and an item to be authenticated. 
         FIG. 6  is a schematic showing in more detail the components of a circular polarizing filter. 
         FIG. 7  is a schematic showing the concept of transmitting information to a remote location and receiving a response in the form of a coupon. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention will be directed in particular to elements forming part of, or in cooperation more directly with the apparatus in accordance with the present invention. It is to be understood that elements not specifically shown or described may take various forms well known to those skilled in the art. 
     Referring now to  FIG. 1 , it shows a flow chart of the steps involved in the method of the invention. The method involves authentication of an object with an affixed label containing a particular type of invisible indicia using a digital camera with a light source to illuminate the label, forming an image from the invisible indicia, and then authenticating the label, and thus the object. 
     Referring now to  FIG. 2 , it shows a schematic representation of the authentication of a label  12  with invisible indicia  14 . The label is constructed from a reflective substrate that preserves the polarization of the incident light, such as a metal. The label is illuminated with a light source  20 . The illuminating light passes through a first polarizing filter  24 . Light that is reflected from the label  12  passes through a second polarizing filter  26  and reaches an imager  22 . 
     Light source  20  and imager  22  are components of a digital camera  18 . The digital camera may be a component of a smart phone or other device. The invisible indicia  14  are deposited onto label  12  in a plurality of regions and are comprised of optically active materials that alter the polarization of light passing through them. Examples of such materials are birefringent polymer layers or chiral molecules. 
       FIG. 3  shows a graphic representation of the label  12  with invisible indicia  14 . The invisible indicia can be human readable, for example alpha-numeric symbols or graphic images, or machine readable, for example linear of two-dimensional bar codes. The invisible indicia can be used to authenticate the label and anything to which the label is affixed. The polarization-altering characteristics of the invisible indicia are different from those of the background; this is represented by two differently shaded areas. To the unaided eye these areas are equally transparent and therefore invisible. The imaging modalities discussed further on convert the different polarization-altering characteristics into different image brightness (indicia versus background), thereby making the invisible indicia visible. 
       FIG. 4  shows an embodiment of the invention where the two polarizing filters  32  and  34  are linear polarizing filters. When linear polarized light  16  created by the combination of light source  20  and first linear polarizer  32  is reflected from the label  12  in the absence of invisible indicia  14 , that is from the background, its polarization remains the same, e.g., if the incident light  16  is polarized along the y-direction in  FIG. 4 , the reflected light  17  will also be polarized along the y-direction. The polarization axis of the second linear polarizer  34  can be oriented along the x direction at a relative angle of 90 degrees with respect to the first linear polarizer  32  such that the reflected light  17  is blocked. Therefore, the label  12  background will appear dark under this type of imaging setup. If invisible indicia  14  are present on label  12 , they will change the polarization direction of the reflected light. This will lead to an incomplete blocking of the reflected light by the second polarizer. Therefore, the invisible indicia will appear bright against a dark background. Alternatively, both linear polarizing filters can be oriented with their polarization axes parallel to each other. In this case the label  12  in the absence of invisible indicia, i.e. the background, appears bright and any polarization-modifying indicia will appear dark in the imager  22  of the camera  18 . 
     Either of the above described methods will result in a differentiation of the invisible indicia from the background thus allowing visualization of the hidden indicia by the imager  22 . Optimal differentiation of the invisible indicia from the background will occur when the linear polarized filters are oriented orthogonal to each other or in parallel with each other; however, differentiation does also occur at other relative orientations of the first and second linear polarizing filters. 
     Once detected by the imager  22  of the camera  18 , the image can be displayed and viewed by an investigator for authentication purposes; a static image can be verified visually, an alpha-numeric code can read and compared to predefined acceptable codes. 
     Additionally, the visualized invisible indicia can be further processed if the digital camera has additional features, for example bar code decoding software; is a component of another device, for example a cell phone; or interacts with another device, for example a printer. The invisible indicia can be decoded, if it is a machine-readable code, and displayed in a human-readable form. It can be transmitted via cell phone or other mobile device. It can be printed. 
     Transmission of the invisible indicia can allow authentication to be done at a remote location. For example, if the invisible indicia are an item-level serial number, the serial number can be transmitted to a remote server containing a database and then cross referenced in the database to either verify the serial number is valid or ascertain additional information associated with that specific item, for example its expected location in the distribution chain. The outcome of the remote authentication step can be transmitted back to the original transmitting device. 
     Referring now to  FIG. 7 , digital camera  18  can transmit invisible indicia via a network  72  to a remote server  74  for authentication. The information transmitted back to digital camera  18  via network  72  can be promotional information such as a coupon  76 , which can be viewed by a display  78 . 
     Upon remote authentication of an object, additional information about the object, such as information related to the sale of the object, can be transmitted to the remote location. Such information could initiate a response in an inventory management system, for example restocking could occur or reordering could occur. 
     In addition to transmitting the invisible indicia, a Global Positioning System (GPS) coordinate of the transmitting device can also be transmitted to a remote location allowing for the identification of the location of the object to be authenticated. This also allows for the identification of the location to which reply information, such as a coupon or restocking information, would be transmitted. 
       FIG. 5  shows an embodiment of the invention where two circular polarizing filters are used as filters  42  and  44 .  FIG. 6  shows a more detailed schematic of how the circular polarizing filter is commonly constructed. The key components are a linear polarizing filter  54  and a birefringent material forming a quarter wave plate  56 . The axis of the linear polarizer  62  is positioned at a positive 45 degrees with respect to the fast axis of the quarter wave plate  58  in order to achieve full left hand circular polarization. For completeness, the slow axis of the quarter wave plate  60  is also depicted. 
     Referring again to  FIG. 5 , when the light, which is created by the combination of light source  20  and first circular polarizer  42 , is reflected from the label  12  in the absence of invisible indicia  14  its polarization changes to right hand circular. Such right hand circularly polarized light propagating toward the image sensor  22  of the camera  18  will first pass the quarter wave plate  56  of the second circular polarizing filter  44  where it will be transformed from right hand circular to linear with the axis of polarization at a negative 45 degrees to the fast axis of the quarter wave plate  56 . This light will be blocked by the linear polarizing filter  54  of the second circular polarizing filter  44 , which has its axis oriented at a positive 45 degrees with respect to the fast axis of the quarter wave plate  56 . Therefore, the label  12  will appear dark under this type of imaging modality. If invisible indicia are present on label  12 , they will change the polarization direction of the reflected light. This will lead to an incomplete blocking of the reflected light by the second polarizer. Therefore, the invisible indicia will appear bright against a dark background in the imager of the camera  18 . The linear polarizing filter  54  of the second circular polarizing filter  44  could also be oriented at an angle of 90 degrees with respect to the linear polarizing filter  54  of the first circular polarizing filter  42 , i.e. at a negative 45 degrees with respect to the fast axis of the quarter wave plate  56 . In the latter case, the invisible indicia will appear dark against a bright background in the imager of camera  18 . 
     Certain light sources such as lasers emit polarized light and may replace light source  20  and first polarizer  24  in an alternate embodiment. 
     The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the scope of the invention. 
     PARTS LIST 
     
         
           12  label 
           14  invisible indicia 
           16  incident light 
           17  reflected light 
           18  digital camera (smart phone) 
           20  light source 
           22  image sensor 
           24  first polarizing filter having a first orientation 
           26  second polarizing having a second orientation 
           32  first linear polarizing filter having a first orientation 
           34  second linear polarizing having a second orientation 
           42  first circular polarizing filter 
           44  second circular polarizing filter 
           54  linear polarizing filter component of the circular polarizing filter 
           56  quarter wave plate component of the circular polarizing filter 
           58  fast axis of quarter wave plate 
           60  slow axis of quarter wave plate 
           62  polarization axis of linear polarizing filter 
           72  network 
           74  remote server 
           76  coupon 
           78  display