Optical Structure

Abstract

An optical device for security and anti-counterfeit applica- tions has a holographic diffractive structure that includes a discrete region that in response to white light illumination generates a holographic image by a process of diffraction of light in one embodiment combined with a paper substrate which also contains a secure mark produced by laser abla- tion of the structure, the mark being characterised by various attributes: variable cut width and pattern, being visible both in reflected light and also in transmitted light, variable depth of cut, variable perforation visible in transmission, variable reflection characteristics. In one embodiment when com- bined with paper based laser mark has elements in both metallised diffractive region and paper region, the marks on different regions showing different characteristics and thereby securely linking diffractive structure and paper substrate and also showing different characteristics of mark- ing pattern on the different materials.