The ever-increasing scale of counterfeiting of documents and consumer products requires new means of verifying their authenticity and preventing the spread of counterfeit goods. Holographic security labels are one of the most well-known and effective means of achieving this goal. Techniques of electron beam lithography and direct laser interference patterning of dot-matrix holograms are among the most widely used to produce these security labels. Due to increasing complexity of modern holographic security labels the ability to inspect the diffraction image produced by such labels has become a necessity in order to design and produce them in an effective fashion. The objective of this internship is to create an algorithm that would be capable of determining a set of dot-matrix hologram parameters that would ensure a near 100% color and image structure correspondence between the true color digital target image and the actual holographic security labels diffraction image. Due to inherent limitations of color printers and electronic screens it is not possible to completely overlay the entire CIE chromaticity diagram. Using an algorithm (created as part of this internship) capable of mixing several pure colors achievable through diffraction of white light enables the creation of true-color dot matrix holograms, capable of portraying a wide variety of colors (much wider than a color printer or LCD/LED screen). Use of true-color holograms compared to ordinary dot-matrix holograms is beneficial because authenticity of such holograms can be easily verified even by an unskilled observer because they portray realistic color images. During this internship the student also got acquainted with lithography technologies used in industrial production of holographic security labels based on dot-matrix technology.
Project is funded by EU Structural Funds according to the 2014–2020 Operational Programme for the European Union Funds’ Investments priority “Development of scientific competence of researchers, other researchers, students through practical scientific activities” under Measure No. 09.3.3-LMT-K-712.
During the internship activities the student learned mathematical methods of describing color and conical diffraction equations, which were used to model the holographic image. The student created an algorithm capable of translating a true color bitmap image into a set of dot-matrix hologram parameters ensuring a complete reconstruction of hologram color and shape of diffraction image. Sufficient accuracy of color reconstruction was ensured, an intuitive graphical user interface and its user manual were also created by the student. The student got acquainted with formation technologies used for production of holographic security labels.
Period of project implementation: 2019-07-01 - 2019-08-31
Project coordinator: Kaunas University of Technology