D. S. Lushnikov

Research of a method and optical system for recording multiplex holograms in a system of holographic memory

The new modified holograms multiplexing method using normal to holographic recording media reference beam incidence and off-normal signal beams incidence is offered for application in holographic memory system having high information capacity and high data rate. Signal beams are located around reference beam concentrically. In this case quantity of multiplex holograms in the same area of recording media is equal to quantity of signal beams. Experimental holographic memory system model applying offered method is tested. Possibility of multichannel optical head application for data recording and retrieving is shown. Offered multiplexing method advantages consist in following: obviating of the necessity of recording media rotation; crosstalk noise free restored data page images; possibility of thin holographic recording media application.

Correlation method for quality control of master matrix used for embossing security holograms

Security holograms (SH) are widely used for authenticity protection of document and product due to difficulties of such a protection mark falsification. Mass production of SH uses widespread technology of hot foil or lavsan paper stamping. The quality of holograms significantly depends on perfection of nickel master-matrix that is used in stamping equipment. We represent the method for automated quality inspection of nickel mastermatrix based on digital processing of its surface relief images. Proposed processing algorithm is based on combination of image spatial frequency analysis and image matching using distortion invariant correlation filters. The results of our method application for real master-matrix inspection are shown in this paper.

The schemes and methods for producing of the visual security features used in the color hologram stereography

Visual security elements used in color holographic stereograms - three-dimensional colored security holograms - and methods their production is describes in this article. These visual security elements include color micro text, color-hidden image, the horizontal and vertical flip - flop effects by change color and image. The article also presents variants of optical systems that allow record the visual security elements as part of the holographic stereograms. The methods for solving of the optical problems arising in the recording visual security elements are presented. Also noted perception features of visual security elements for verification of security holograms by using these elements. The work was partially funded under the Agreement with the RF Ministry of Education and Science № 14.577.21.0197, grant RFMEFI57715X0197.

Optical position encoder based on four-section diffraction grating

Optical position encoder consists of movable coding grating and fixed analyzing grating. Light passing and diffracting through these two gratings creates interference signal on optical detector. Decoding of interference signal phase allows to determinate current position. Known optical position encoders use several accurate adjusted optical channels and detectors to gather several signals with different phase for higher encoder accuracy. We propose to use one optical channel with several-section analyzing diffraction grating for this purpose to simplify optical scheme and adjusting requirements. Optical scheme of position encoder based on four-section analyzing diffraction grating is developed and described in this paper.

The small-sized ultraprecision sensor for measuring linear displacements

The article describes a new optical scheme of noncontact sensor for measuring linear displacement - linear encoder. This sensor is an optical device in which the measurement of displacement is performed by analyzing the optical signal, which pass through two diffraction gratings, one of which is moved relative to the other. The optical signal is obtained by the diffraction of light in these diffraction gratings and subsequent interference of diffracted beams. Often this type of sensors are multi-channel devices with symmetrically positioned of detectors. This scheme is proposed to use a multisection phase mask that allows to make a small-sized sensor. Sections of this multi-section phase mask are the optical windows and they made the final interference signals to be shifted relative to each other in phase. The number of sections in the multi-section phase mask can be varied. Estimated sufficient number of sections is four or more.

Experimental study of the method of recording color volume security holograms on different photosensitive materials on the base of the diffuser with a narrow indicatrix of laser radiation

The paper presents the practical results of recording holographic stereograms. Advantages and disadvantages of methods for producing holographic stereograms using diffusers with different indicatrices scattering of the radiation in the object branch and without the use of a diffuser are presented. A new security element - multi-color microtext, is presented. Shows how to use multi-color microtext as a hidden security element. The method of multi-color microtext visualization is shown. The work was partially funded under the Agreement with the RF Ministry of Education and Science no. 14.577.21.0197, grant RFMEFI57715X0197.

High-aperture diffractive lens for holographic printer

The optical scheme of holographic printer for obtaining of holographic stereograms with an increasing field of view is proposed. Conventional holographic printers allow obtaining holographic stereograms with the field of view up to 90°. Proposed scheme allows increasing field of view up to 120°. The optical scheme is based on a diffuser and a diffraction optical element, the high-aperture diffractive lens. The experience of using the composite holographic lens and the amplitude diffractive lens based on a binary Fresnel zone plate as a high-aperture diffractive lens is described. Samples of high-aperture diffractive lens with f-number f/0.3 are obtained and investigated. Samples of holographic stereograms are obtained using samples of high-aperture diffractive lens.

Plasmonic spectral filters based on diffraction gratings

Method for the analysis of plasmonic gratings is developed. The mathematical research of the spectral-angular characteristics of plasmonic gratings is realized. The dependency of spectral-angular characteristics on geometric parameters of the plasmonic grating are disclosed. Samples of plasmonic gratings are obtained. The results of mathematical modeling and theoretical studies are confirmed by the experimental samples. Spectral-angular characteristics of the plasmonic gratings samples qualitatively repeat theoretically modeled characteristics.

Optimization of holopixel size and perspectives number in holographic stereogram

The mathematical model of signal conversion carried out by holographic optical element (HOE) in holographic stereogram (HS) is presented. Expression for the point spread function (PSF) of HOE in the plane of an observer is obtain as well as the expression for the optimal number of perspectives and plans of HS. Relationship between the observation distance, the size and number of perspectives in HS HOE are considerate. Constraints and future prospects of art and security holography development are disclose. The approach how to optimize HS parameters (such as holopixel size and perspectives number) for current 3D image and HS application is proposed.

Modeling of spatial-frequency spectrum of security holograms and optoelectronic spectrum analyzer for their identification in real time

The urgency of application of the optoelectronic analyzer for security holograms identification in real time for paper documents and plastic cards is obvious. The spatial-frequency spectrum analyzing method for security hologram is offered. The essence of the method consists in reception of the security holograms (SH) microstructure spatialfrequency spectrum (SFS), description SH SFS by means of integral, peak and combined parameters, and identification analyzed SH by the correlation recognition method by comparison of analyzed SH SFS parameters with reference SH SFS parameters. For this purpose it is enough to illuminate SH by laser or light-emitting diode (LED) radiation to construct by Fourier lens SH SFS, to register it with matrix receiver of radiation, and to process a signal in the electronic block. The mathematical model of a spatial-frequency spectrum of the SH is constructed and investigated. We will consider SH SFS in the limited sector of spatial frequencies. It is possible to describe SH SFS in terms of integral parameters, peak parameters, and their combinations. A series of such parameters is offered. Several SH identification algorithms is offered. The optical scheme of optoelectronic spectrum analyzer for identification SH is offered and experimentally investigated.