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.
The basic aspects of animated and stereographic rainbow images making technology are considered in this paper. These
images are devoted to include in Optical Security Devices (OSDs) in order to increase its structure complexity and to
improve its protective properties. They provide on the one hand the simple identification on the visual level of
verification and on the other hand the sufficient reliability against counterfeit. The last one is achieved at first by the
division of the elemental unit on the regions of any adjusted shape with outline of the precision that is inaccessible for
recreation without Electron Beam Lithography Equipment (EBLE), which is used for OSDs recording, and, secondly,
by the used encoding methods.
In the context of the paper the theoretical discussion of the diffraction on elemental diffractive grating was carried out.
The acquired results have been allowed to create the software utility that models the behaviour of the anigram or
The analysis of examples of the sythetized by the given methodology anigrams shows that there is peculiar for them the
effects of the stereoscopic perception. So the investigations on combined methodology of animated stereographic
images synthesis were carried out. There were recorded the stereographic, animated and the animated stereographic
images as a parts of demonstrational holograms of STC “Optronics”, Ltd.
In the context of the paper there are represented the theoretical foundations and technological aspects of creation of the
Optical Security Devices by Polygram technology. This technology implies the images of different types combining. There are generally discussed the Computer-Generated Rainbow Holograms (CGRHs) of 3D images. This type of holographic images is distinguished by its reliability against counterfeit, caused by the fact it requires matchless in this field precision of printing system, using extreme for the Electron Beam Lithography Equipment, which is applied for
the recording, values of the stamp sizes. On the other hand CGRHs certainly distinguish from similar optical and stereographic images, so they can be easy recognized on the visual level of the verification and don’t need application of any tools. The theoretical basis of the CGRHs creation is strictly presented in this paper. The special attention is paid to the right choice of the non-linear quantization parameters. This paper is mainly concentrated on the investigation of the CGRH combining both with another CGRHs and with the other different images implying by the Polygram technology. The methods of the space restriction of the separate CGRH topology with the information loss and without it are compared. There are carried out the investigations of the
influence of the additional images on visual perception of the CGRH.
This work deals with Computer-Generated Rainbow Holograms (CGRHs), which can restore the 3D images under white light. They are devoted to include in Diffractive Optically Variable Image Devices (DOVIDs) that are currently widely used for security needs. CGRHs prevent counterfeiting due to the complexity of recreation on the one hand and allow the simple identification at the first (visual) level of verification on the other hand. To record it the Electron Beam Lithography (EBL) is used. The CGRH computation process is conventionally divided on two parts: synthesis and recording. On the synthesis stage, firstly, the geometrical and optical constants of recording scheme are determined, secondly, the basic parameters accounting for discretization of ID in hologram plane are defined and, finally, the calculation of the Interferogram Data (ID) - the array of Bipolar Intensity (BI) values - is carried out. This calculation is performed separately in each independent horizontal slice of object space and hologram plane. On the recording stage a suitable quantization parameters are chosen and transformation of ID into the multilevel rectangle data appropriate for EBL is accomplished. The investigations on optimization of synthesis and recording of the multilevel CGRHs of 3D images integrated in Polygrams are presented here. So the rules for definition of the appropriate discretization parameters were finding out. Advantages of using non-linear quantization that implies condensing of quantization levels near the BI zero were explored. The random deviation of location and direction of elemental hybrid radiating area was applied.
Computer-generated holograms (CGHs) integrated within combined optical-digital security devices (CO/DSDs) are described in this work. They can restore the monochrome and color 3D images in white light. For their recording the Electron Beam Lithography (EBL) is used. Our investigations on optimization of synthesis and recording of the CO/DSDs with the integrated in it multilevel CGHs of 3D images possessed horizontal parallax only (HPO) are presented here. The CGH fabrication process is mainly composed of two parts: calculating of the interferogram data (ID) and their recording. Calculation of the ID is done as follows: firstly, the geometrical and optical constants of recording scheme and the object surface represented by the elemental self-radiating areas, are determined, secondly, the basic parameters accounting for discretization of ID in hologram plane is defined. The ID values can be derived by calculation of the necessary elemental object areas bipolar intensities sum. Next, over suitable quantization of ID, recording of the rectangle data appropriate for EBL onto glass coated with non-organic photoresist based on As40S40Se20 is performed. We have also investigated reciprocal influence of an optical part of the CO/DSD and a digital one.
Modern holographic security devices used as emblems against counterfeiting are being more difficult as they should oppress criminal world. 2D, 3D, 3D rainbow holograms or simple diffraction structures protecting documents can not be acceptable against illegal copying of important documents, banknotes or valuable products. Recent developments in technology of Optical variable devices permit world leaders to create more advanced security elements: Kinegrams, Exelgrams, Pixelgrams, Kineforms. These products are used for protecting the most confidential documents and banknotes, but now even their security level can not be enough and besides their automatic identification is vulnerable to factors of instability. We elaborate new visual security devices based on the usage of expensive and advanced technology of combined optical/digital security devices. The technology unites digital and analogue methods of synthesis and recording of visual security devices. The analogue methods include techniques of optical holography - different combinations of 2D/3D, 3D, 2D/3D + 3D structures. Basing on them the design with elements of 3D graphics including security elements and hidden machine- readable images are implemented. The digital methods provide synthesis of optical variable devices including special security elements, computer generated holograms and Kineforms. Using them we create determined and quasi-random machine-readable images. Recordings are carried out using the combined optical and electronic submicrometer technology elaborated by Optronics, Ltd. The results obtained show effectiveness of the combined technology permitting to increase the security level essentially that should increase tamper and counterfeit resistance during many years.
Here is considered the 3D optical display with movable intervening medium (MIM) for the 3D dynamic stages representation and the experimental results of its basic elements creation are provided. MIM implements two important functions in the proposed display architecture: it forms the secondary light source (SLS)--the element of 3D stage resolution and fulfills scanning by depth (provides forming of stage's planes). The dependence of the SLS parameters from the primary source, MIM structure and shape of its surface have been investigated theoretically and experimentally as well as their connection with 3D stage parameters and 3D display architecture at all. With the aim of display parameters optimization the researches have been carried out for the diffusers with surface- and volumetric-scattering with different statistical parameters. It has been shown that the usage of volumetric diffusers permits to expand the directness diagram to 160 degrees by means of SLS brightness decreasing, to make it be independent from the angle of primary beam falling, to increase the resolution and improve conditions of stage perception by means of speckle decreasing. There have been made calculations of 3D stages formed by MIM non-linear distortions and chosen the optimal shape of MIM surface.