This patent document discloses physical documents including metameric ink pairs. One claim recites a document comprising: a first surface; a second surface, in which the first surface comprises a first set of print structures and a second set of print structures, in which the first set of print structures and the second set of print structures collective convey an encoded signal discernable from optical scan data representing at least a first portion of the first surface, in which the first set of print structures is provided on the first surface with a first ink and the second set of print structures is provided on the first surface with a second, different ink, and in which the first ink and the second, different ink comprise a metameric pair. Of course, other claims and combinations are described as well.

A method for checking the authenticity of products, by checking an image (A) of a product. The proof of authenticity is not visible to the human eye and cannot be copied. This is characterized in that a code stored in a halftone image by manipulation of dots and/or a manipulated field bounded in the halftone image can be read by means of an optical device and compared with a retrievable value in at least one database. In at least one field (F1 to F5) a part of a serial number is determined which describes the structure of the serial number and a hash function used for transmitting the serial number to the database, and this is also characterized in that the serial number is subsequently assembled and encrypted with the corresponding hash function.

A media handler for detecting counterfeit media is described. The media handler comprises: a plurality of discrete sensors distributed along a transport path operable to transport a media item, and a controller operable to receive signals from the plurality of discrete sensors. The controller is also operable to make a decision on validity of the transported media item based on the received signals.

A method for producing security elements in an image which are not visible to the human eye and which cannot be copied, in particular for checking the authenticity of images. The image is imaged by means of a halftone, the halftone consisting of individual image dots arranged adjacent to each other. This is characterized in that at least one field having a random geometric shape or freeform is defined in the image/the halftone. By means of manipulation of image dots in the field and/or by means of manipulation of the entire field, an encrypted information that cannot be copied is stored for comparison with at least one database and the serial number is displayed by means of contours formed in the halftone.

A method for producing security elements in an image which are not visible to the human eye and which cannot be copied, in particular for checking the authenticity of images. The image is imaged by means of a halftone, the halftone consisting of individual image dots arranged adjacent to each other. This is characterized in that at least one field having a random geometric shape or freeform is defined in the image/the halftone. By means of manipulation of image dots in the field and/or by means of manipulation of the entire field, an encrypted information that cannot be copied is stored for comparison with at least one database and the serial number is displayed by means of contours formed in the halftone.

A method for checking the authenticity of products, by checking an image (A) of a product. The proof of authenticity is not visible to the human eye and cannot be copied. This is characterized in that a code stored in a halftone image by manipulation of dots and/or a manipulated field bounded in the halftone image can be read by means of an optical device and compared with a retrievable value in at least one database. In at least one field (F1 to F5) a part of a serial number is determined which describes the structure of the serial number and a hash function used for transmitting the serial number to the database, and this is also characterized in that the serial number is subsequently assembled and encrypted with the corresponding hash function.

A method of detecting a counterfeit item using a contactless scanner includes contactlessly scanning at least a portion of an item to generate a scanned image of the at least a portion of the item, wherein the at least a portion of the item comprises a graphic, identifying elements in the scanned image that correspond to elements in the graphic, measuring the identified elements to generate a plurality of element measurements, determining whether the item is counterfeit based on a comparison between at least one element measurement of the plurality of element measurements and at least one reference element measurement that is associated with an authentic version of the item, and in response to determining that the item is counterfeit, generating an alert indicating a detection of a counterfeit item.

A method of detecting a counterfeit item using a contactless scanner includes contactlessly scanning at least a portion of an item to generate a scanned image of the at least a portion of the item, wherein the at least a portion of the item comprises a graphic, identifying elements in the scanned image that correspond to elements in the graphic, measuring the identified elements to generate a plurality of element measurements, determining whether the item is counterfeit based on a comparison between at least one element measurement of the plurality of element measurements and at least one reference element measurement that is associated with an authentic version of the item, and in response to determining that the item is counterfeit, generating an alert indicating a detection of a counterfeit item.

This patent document discloses physical documents including metameric ink pairs. One claim recites a document comprising: a first surface; a second surface, in which the first surface comprises a first set of print structures and a second set of print structures, in which the first set of print structures and the second set of print structures collective convey an encoded signal discernable from optical scan data representing at least a first portion of the first surface, in which the first set of print structures is provided on the first surface with a first ink and the second set of print structures is provided on the first surface with a second, different ink, and in which the first ink and the second, different ink comprise a metameric pair. Of course, other claims and combinations are described as well.

The application discloses apparatus and systems for authenticating physical object, identification documents and security documents. Some such methods and apparatus involve signal encoding or digital watermarking.