| 摘要 |
PCT No. PCT/GB91/02069 Sec. 371 Date Jun. 10, 1993 Sec. 102(e) Date Jun. 10, 1993 PCT Filed Nov. 22, 1991 PCT Pub. No. WO92/09444 PCT Pub. Date Jun. 11, 1992.An authenticatable item and security device carry a number of symbols (4A, 4B, 4C, 6A, 6B, 6C) identifiable to the naked eye, there being at least two sets of at least three symbols. All the symbols within a set are substantially identical, are positioned in a non-overlapping, regular geometric arrangement, and at least one common viewing angle of inclination, exhibit substantially the same optical performance, the optical performance varying with inclination viewing angle. |
