Latent Masked Image
An image formed by lines, strokes of a certain geometrical shape, or raster elements. The latent image is applied by the same printing technique as the background pattern and does not differ from it in color. Its contours are hardly visible to the naked eye. The image can be visualized as a letter, figure, or geometric shape under magnification in white light.
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Fig. 1. Sudan. Passport issued in 2014:
a — page spread (pages 26–27). Paper substrate; b — the same. Page 27. Background pattern containing a latent image. The symbols SDN are formed by inclined strokes invisible to the naked eye against the background pattern. Offset printing; c — the same. Page 26. Background pattern containing a latent image. The background pattern masks the symbols SDN that are invisible to the naked eye. Offset printing; d — the same. Zoomed fragment. The symbols SDN are visible under magnification