Methods of protecting security documents from counterfeiting

A security document protected from counterfeiting comprising a substrate and including at least one security element, wherein the security element contains a concealed Fourier pattern produced from a master Fourier profile, and wherein the concealed Fourier pattern is applied to the security document by printing or embossing, such that when a counterfeit document is produced without knowledge of the master Fourier profile and the counterfeit security document is scanned or imaged and subjected to a Fourier transform, the resulting test Fourier pattern produced differs from a master Fourier pattern corresponding to the master Fourier profile.

A method of protecting a security document from counterfeiting comprising:

• applying at least one security element containing a concealed Fourier pattern to the security document wherein the concealed Fourier pattern is produced from a master Fourier profile, and wherein the concealed Fourier pattern is applied to the security document by a cylinder or plate bearing the master Fourier profile,
• whereby when a counterfeit security document produced without knowledge of the master Fourier profile is scanned or imaged and subjected to a Fourier transform, the resulting test Fourier pattern differs from a master Fourier pattern corresponding to the master Fourier profile for the authentic security document.

A security document protected from counterfeiting comprising a substrate and including at least one security element, wherein the security element contains a concealed Fourier pattern produced from a master Fourier profile, and wherein the concealed Fourier pattern is applied to the security document by a cylinder or plate bearing the master Fourier profile, such that when a counterfeit security document is produced without knowledge of the master Fourier profile and the counterfeit security document is scanned or imaged and subjected to a Fourier transform, the resulting test Fourier pattern produced differs from a master Fourier pattern corresponding to the master Fourier profile.