The article discusses the use of computer-generated holograms (CGHs) for the application as one of the security features in the relief-phase protective holograms. An improved method of calculating CGHs is presented, based on ray-tracing approach in the case of interference of parallel rays.
Software is developed for the calculation of multilevel phase CGHs and their integration in the application of security holograms. Topology of calculated computer-generated phase holograms was recorded on the photoresist by the optical greyscale lithography. Parameters of the recorded microstructures were investigated with the help of the atomic-force microscopy (AFM) and scanning electron microscopy (SEM) methods. The results of the research have shown highly protective properties of the security elements based on CGH microstructures. In our opinion, a wide use of CGHs is very promising in the structure of complex security holograms for increasing the level of protection against counterfeit.
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