| 摘要 |
An optically decodable security document is provided comprising a security image area defined on a face of the document. The security image area is divided into a plurality of image element cells defining an array of image element cells across the security image area. The image element cells define first and second diagonal axes and a cell center positioned at the intersection of the first and second diagonal axes. A first type of printed tiling element is printed in selected ones of the image element cells to define a printed security image within the security image area. A second type of printed tiling element is printed in selected ones of the image element cells to define a printed complementary security image within the security image area. Individual ones of the first and second types of printed tiling elements comprise printed units positioned within the respective image element cells so as to define substantially equal printed tones defined by the printed units across the first and second types of printed tiling elements. The printed units within the first and second types of printed tiling elements are arranged such that (i) an imaging band extending across the security image and the complementary security image, parallel to one of the first and second diagonal axes, demarcates a security image band in the security image area and a complementary security image band in the complementary security image area, and (ii) the security image band and the complementary security image band are characterized by substantially different intra-band printed tones defined by the printed units within the security image band and the complementary security image band. |
