Anti-scan / Anti-copy Pattern
A background image which consist of raster elements or strokes forming a pattern. When copying/scanning a document, text ("COPY", "VOID", etc.) invisible to the naked eye appears on copies or moire appears as rainbow lines, bright and dark stripes, and spots, etc.
a
b
c
Fig. 1. Egypt. Special passport issued in 1999:
a — page 52. Polymer substrate. The area with the anti-copy pattern is marked with a frame; b — the same. Black-and-white copy made on a copy machine. The word COPY in the bottom part of the page has dark contours, is visualized when copying at 200 dpi resolution; c — the same. The symbols of the word COPY are invisible to the naked eye. They are formed by inclined strokes printed at high-resolution. Offset printing
a
b
c
Fig. 2. Latvia. Passport issued in 2002:
a — data page. Paper substrate. The fragment of the anti-copy pattern is marked with a frame; b — the same. Zoomed fragment of the anti-copy pattern formed by lines. Offset printing; с — the same. Moire in the form of dark and bright multidirectional stripes is visualized when copying/scanning at 200 dpi resolution. It appears as a result of two regular patterns overlay: strokes of the original printed image and CCD (charge-coupled device) image sensors of digital printers or copiers