HOLOGRAPHIC SECURITY DEVICE

摘要

A holographic security device in which the holographic effect is generated by the diffraction of light by a surface relief pattern on a film and which, when illuminated, generates a moire pattern produced from a pair of overlapping, regular arrays (3, 4) of lines or dots. Each array has a line of symmetry (7, 8), the lines of symmetry being aligned. The device exhibits an ordered variation in the form of the observed moire patterns in a direction parallel with the alignment direction of the lines of symmetry and a colour variation transverse to the alignment direction.