| 摘要 |
A secure and self-verifiable image is formed by an array of image dots 30 on one side of a pellucid stratum or film 10 and a corresponding array of light-transmitting apertures 21 in a dark screen 20 on the other side of film 10, with image dots 30 being offset from the axes of apertures 21 so that the image is viewable only by light passing obliquely through film 10 at an angle that intersects arrayed apertures 21 and dots 30. Both apertures 21 and dots 30 occupy up to about 15% of the total area and the array spacing is at least 40 dots per centimeter. The reflective density of the interaperture regions of dark screen 20 is at least 1.6, and pellucid film 10 is at least 0.05 mm thick.
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