| 摘要 |
PURPOSE: To facilitate discrimination of a genuine article from a false one by providing plurality of designs divided into a plurality of meshes containing optical diffraction elements having spatial frequencies in specified numbers or more. CONSTITUTION: A surface pattern has designs divided into meshes in the number of M containing optically active diffraction elements having spatial frequencies of 10/mm or more. Each mesh 6 of which the maximum dimensions are smaller than 0.3 mm is divided into pixels 7a-7f in the number of N each having a diffraction element 8 and each diffraction element 8 forms each pixel of the designs 3 in the number of N. Since a parameter of an indentation structure 9 which each of the diffraction elements 8 has is so determined as to correspond to each design, each of the designs 3 in the number of N can be recognized visually in a prescribed direction 15 of observation of the surface pattern. By the visual recognition at different angles of observation, according to this constitution, the genuineness of the pattern can be discriminated even by a novice in the case when it is irradiated normally by daylight or artificial light. |
