Security documents

摘要

A security document for example a bank pass book has printed on one portion thereof an area containing scrambled indicia and on another portion a transparent area configured as a reading screen for unscrambling the indicia. These two portions are arranged so as to be superimposable to enable the indicia to be read. The first-mentioned area consists of a regularly lined image of the indicia on a regularly lined background the lines of the background being displaced laterally relative to the lines of the indicia (Figure 11) over which is an overall random pattern or "noise" (Figure 12). Photographic and computer methods of generating the scrambled indicia are disclosed.