The goal of a present research is to develop a method for production of multilevel Diffractive Optical Elements
(DOEs) for use in Digital Security Holograms, using the direct-writing maskless lithography system.
It is well known that one of the basic functions of security holograms is the maximal complication of their nonauthorized
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 Optical Variable Device (DOVID) is integration into DOVID's structure of a Concealed Laser-Readable
Image (CLRI). Traditionally CLRI is a 2-D Computer-Generated Hologram (2-D CGH), which is a digitized
Interference Fringe Data (IFD) structure, computed under the scheme of Fourier-hologram synthesis. Such hologram
provides inspection of second level with portable laser reading devices. While it is being read, two (+/- 1 order of
diffraction) identical images are formed. In this work a special kind of CGH, which restores image only in one
diffractive order or two different images in +1 and -1 orders of diffraction proposed.
3D computer-synthesized hologram - is one of the most promising technologies that today is used in modern optical
protection elements. Usage of 3D CGH as hologram component allows not only to increase the level of their
authenticity but also expand the field of designer solutions, which is very important for increase of hologram quality.
Without completely substitute of classical 2D/3D elements 3D CGH technology allows to provide them with especial
In the present paper the comparative analysis of organic and inorganic resists for registration of optical/digital holograms is described. The purpose of researches - to find optimum recording medium for record of the combined holographic protective elements. Organic photoresist S1800, organic PMMA electron-resist and inorganic resist - Chalcogenide Glass System (HGS) As40S 60-x Se x (where x=20,30,40) were investigated. Besides this, information characteristics resist layers of HGS were investigated with the purpose of definition optimal recording modes of optical microstructures by Electron Beam Printing System (EBPS). The correcting method of system response on forming of interactive diffraction grating is offered. It is shown, that maximal electron sensitivity have resist layers As40S40Se20. It was revealed during researches, that for this task an organic resist S1800 series and inorganic - As40S40Se20 are suitable. On results of our measurements it has been established that organic resist S1800 is more sensitive (more than 10 times) in comparsion with HGS and provides higher resolution (about 2500 lines per millimeter). Providing of high resolution is very important for registering Computer Generated Holograms (CGH), especially 3-D images holograms.
In this report, an advanced method of calculation of computer-generated holograms (CGHs) for reconstructing 3-D images is proposed. Commonly CGH producing process comprises two parts: synthesis and recording. On the synthesis stage the calculation of the Interferogram Data (IFD) - the array of Bipolar Intensity (BI) values - is carried out. On the recording stage a suitable quantization parameters are chosen and transformation of IFD into the multilevel rectangle data appropriate for Electron-Beam Printing System (EBPS) is accomplished. In proposed method the IFD calculation is implemented in Fresnel approaching with the direct ray tracing. The representation of an object as the Hybrid Elemental Self-Radiating Areas (HESRAs) is used. Such kind of the object representation more accurately corresponds for objects of the scene behavior. Advantages of using non-linear quantization that implies condensing of quantization levels near the BI zero were considered. The influence of random location and direction deviation of elemental hybrid radiating area was explored. In the experimental result, we obtained monochrome computer-generated hologram of 3-D image, suitable for integration into the typical rainbow hologram.