OBJECT HAVING A HOLOGRAPHIC SECURITY FEATURE AND METHOD FOR MANUFACTURING SUCH A FEATURE

摘要

An optical security feature, e.g. for a banknote or other security documents, comprises a first and a second holographic layer (6, 7) arranged on top of each other. Each layer comprises a comparatively simple reflective volume hologram (8, 9), such as it can e.g. be recorded by the interference pattern of two Gaussian light beams. The volume holograms (8, 9) have different grating spacing and/or orientation as well as different extension such that the observer can distinguish and verify them easily. The simple nature of the holograms make the security feature easy to manufacture, while its two-layer structure makes it hard to copy and yields high diffraction efficiency.