Machine-readable security document and method of preparing the same

Abstract

A security document and its method of preparation are provided wherein a security image area on the face of the document is designated. The security image area comprises a two-dimensional array of security image blocks. Security image elements and the complementary security image elements in respective security image blocks are arranged such that the security image element and the complementary security image element portions occupy respective first and second percentages of each of the security image blocks to define respective characteristic relative occupation values (CROVs) for each security image block. The respective CROVs are substantially equivalent among a plurality of the security image blocks. A target CROV is established. Respective security image element portions and respective complementary security image element portions are established such that the respective security image element portions occupy a first percentage of a selected security image block and the respective complementary security image element portions occupy a second percentage of the selected security image block. A relative value of the first and second occupation percentages is determined and compared with the target CROV. At least one of the complementary security image element portion and the security image element portion is adjusted, if the comparison indicates a significant disparity between the first and second occupation percentages and the target CROV, such that the relative value of the first and second occupation percentages substantially corresponds to the target CROV. Finally, a security document including the two-dimensional array of security image blocks is generated, wherein each of the security image blocks is occupied by the security image elements and the complementary security image elements.