Patent ID: 8509492

Claim:
A method for determining the presence of color shifting elements on documents, the method comprising the steps of: (a) passing a document past an image sensor; (b) sequentially illuminating said document using at least two alternating azimuths of illumination, wherein the document is divided into discrete successive sections and a predetermined azimuth of illumination is applied to each section as the document passes said image sensor until a predetermined area of the document is imaged, producing an interleaved, multi-azimuth image of said area of the document, wherein a first one of the at least two azimuths of illumination is associated with a first light source at a first azimuth relative to the document, wherein a second one of the at least two azimuths of illumination is associated with a second light source at a second azimuth relative to the document, and wherein the first azimuth is different from the second azimuth; (c) applying a transformation function to said interleaved, multi-azimuth image to generate color values for each azimuth of illumination; and (d) comparing said color values, wherein variation in color value between azimuths of illumination indicates the presence of a color shifting element on the document.