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Semiconductor Physics, Quantum Electronics & Optoelectronics. 2006. V. 9, N 4. P. 085-090.
Kinoform synthesis as an improved method
to form a concealed image in optical security devices
1Taras Shevchenko Kyiv National University (Ukraine)
2Optronics (Ukraine)
3V. Lashkaryov Institute of Semiconductor Physics, NAS of Ukraine (Ukraine)
Abstract. It is well known that one of the basic functions of security holograms is the
maximal complication of their non-authorized reproduction, in other words –
counterfeiting. To solve the problem, concealed images that can be observed only under
special conditions are placed into a structure of the hologram. A popular way to place
concealed image in Diffractive Optically Variable Image Device (DOVID) is integration
into DOVID's structure of a Concealed Laser-Readable Image (CLRI). Traditionally
CLRI is a 2D Computer-Generated Hologram (2D CGH), which is a digitized
Interference Fringe Data (IFD) structure, computed under the scheme of Fourierhologram synthesis. Such hologram provides inspection of the second level with portable
laser reading devices. While it is being read, two (+/– 1 order of diffraction) identical
images are formed. It is very interesting to achieve a CGH, which restores the image only
in one diffractive order or two different images in +1 and –1 orders of diffraction.
Keywords: concealed image, kinoform methods, 2D CGH, CLR.
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