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Optically variable and machine-readable device for use on security documents
| Details |
Inventors: Mowry, Jr., William H.; Castle, William J.; Neitman, Robert L.;
Assignee: The Standard Register Company (Dayton, OH)
Primary Examiner: Bell; Paul A.
Assistant Examiner:
Attorney, Agent or Firm: Killworth, Gottman, Hagan & Schaeff
An optically variable device for use on security documents to deter unauthorized reproduction is provided which contains a warning message that is not readily apparent to an observer but that reproduces as a visible warning message when copied. The device comprises a pattern of light reflecting surfaces which comprise a reflection diffraction grating having a plurality of grooves that vary in orientation and blaze angle. In an alternative embodiment, a machine-readable optically variable device is provided in which the pattern of specularly light-reflecting surfaces produces a machine-readable message in response to light impinging on the device. |
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DETAILED DESCRIPTION The present invention meets that need by providing an optically variable device for use on security documents which is inexpensive to produce and deters unauthorized reproduction by the use of a concealed message on the device which is not readily apparent to the user but reproduces as a visible warning message when copied.
The present invention also provides a machine-readable optically variable device for use on substrates.
By optically variable, we mean a device which varies in appearance depending upon the point from which it is viewed.
In accordance with one aspect of the present invention, a security document is provided comprising a printed document substrate and an optically variable device secured to the substrate having a concealed warning message therein.
The optically variable device comprises a pattern of specular light reflecting surfaces which reproduces as a visible warning message when copies of the document are produced on digital or analog copiers or printers.
However, the warning message is not readily apparent on the original document because the specular reflection caused by a normal diffused light source "hides" the message from an observer.
Diffused light is directed onto the diffraction grating from all angles while the illuminating light in a copier is directed onto the diffraction grating at one specific angle.
Thus, the message becomes readily apparent on a reproduction.
In one embodiment, the pattern of specular light reflecting surfaces comprises a reflection diffraction grating having a plurality of grooves that vary in orientation and blaze angle.
The reflection diffraction grating preferably comprises a prismatic foil, but may also comprise a metallic foil, holographic foil, metallized plastic, or an embossed foil.
However, the invention is not intended to be limited to these materials, but rather may include any optically variable materials having properties which may reproduce a visible warning message on optical analog or digital printers and copiers
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LCD 
