Generalized fresnel lens in security, light managment and holographic packaging applications

Pawel Stepien
Marcin Badenski Polish Holographic Systems, Poland
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The eye of a man is perfectly designed by nature, but still it can be deceived. This attribute is the basics of holography, especially useful for making the 3D effects. In traditional rainbow holograms the diffractive pattern is recorded to be visible in white light as 3D image, but with parallax in one direction only. Is it possible to easily create a computer generated pattern which will be visible by the viewer as 3D image with parallax in all directions (like a relief)? Yes, it can be achieved using generalized Fresnel lens to calculate structures then recorded by optical lithography. The Kinemax technology was originally designed for exposing rainbow holograms with best diffraction efficiency. The further development of both optics and software enabled the possibility of using of Kinemax system as optical lithography unit. The essential feature of optical lithography is exposing images directly, with very high resolution. The Fresnel lens is well-know method of imitating thick real lens by the flat pattern, which modulates the phase of light. It is possible to imitate spherical lens, cylindrical lens etc. But it is also possible to make a lot more complicated designs, which will be visible for the viewer as full 3D reliefs, being less than micron thick. The exposed pattern is calculated in the similar way as the pattern of the Fresnel lenses. New Kinemax-Litho system combines generalized Fresnel lens calculation technique with optical lithography recording, allowing to expose very complicated, highly detailed designs. However the designing process is very simple, does not require much of technical or theoretical knowledge. The depth of 3D relief is represented on the design by the level of gray in a 8-bit grayscale bitmap file, in the way similar to the change of colors on the relief map. So the only limitations in preparing the designs is imagination and graphical designing abilities.