V. V. Markin

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.

The optical scheme for recording of miniature light guide holographic indicator

The holographic optical elements (HOE) for holographic indicators and methods of their production on the photosensitive materials are described. A distinctive feature of this optical scheme is the zone record of diffraction gratings and HOE, i.e., grating is divided into separate fragments that stitching at the recording process with a high-precision motion system of the plate.

Composite holographic screens for the stereoscopic or multiview color image display

The transmission type holographic screen is a special kind of scatterer, which is used to concentrate the light from the projected image into small size spot (viewing zone). As a result, different images can be delivered to each observers eyes and it is possible to display the stereoscopic images. The most serious problem related with the holographic screen is its high dispersion and aberrations which cause the viewing zone distortions and poor color reproduction in the displayed image, especially in the screen corners. Both of the above mentioned drawbacks become more prominent when the screen size becomes larger. To compensate the screen dispersion, a diffuser in the form of a long narrow stripe directed to the reference beam axis is used for an object. The length and position of the diffuser are calculated to make the reconstructed images of it for all wavelengths of the white light projector to be superposed in the viewing zone. To solve the aberrations problem, a big size screen was composed by mosaicking many sub-screens which were recorded individually in the specially optimized setup. For example, when the sub- screen is recorded for the edge part of the screen, the diffuser was tilted different direction to provide proper superposition of the reconstructed diffuser images. For each sub-screen, the diffuser is tilted such that it is in nearly the same plane with the reference beam axis. The sub-screens are recorded on the holographic photoplates PFG-01 (Russia) with an optical set-up optimized for each sub-screen by adjusting the diffuser position and its tilt angle. All necessary parameters are calculated by considering the light beam path for different wavelengths in the visible spectrum. The size of each sub-screen is 40 X 30 cm2. Eight sub- screens are mosaicked to obtain a composite holographic screen with size 80 X 120 cm2. The screens have been used to display the full color stereoscopic images from slide projectors. The distances between the projector and the composite screen, and the screen and a viewer are set to 4 m and 3.5 m, respectively.

Optical position encoder based on structured head diffraction grating

Optical position encoders working according to the interference method consists of a measurement scale and a measuring head moving along each other. The scale has a reflection diffraction grating on its surface and the measuring head has a transmission diffraction grating with same period inside. Laser light passing and diffracting through these two gratings creates an interference signal on an optical detector. Decoding of the interference signal phase allows to determinate current position. Known optical position encoders use complex optical schemes and some phase optical elements to form several quadrature signals with different phase for higher encoder accuracy. Previously we researched such kind of schemes [1, 2]. In this paper we propose to use a common optical scheme without phase elements but with a complex structured measuring head grating for this purpose to simplify an optical scheme and alignment requirements. The optical scheme of position encoder based on measuring head grating with specific structure is research and described 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.

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.

Holographic memory based on computer generated Fourier-holograms

Classic holographic memory systems use two-beam approach based on fixation of interference pattern between object and reference coherent beams on holographic recording medium. The size of single pattern is about several micrometers. High precision optical set up is required to form such a microhologram, that is the reason of excessive price for holographic recording devices. Methods of computer holographic synthesis allow to calculate holographic patterns numerically as 2D images. These images can be realized with the use of spatial light modulator, then reduced in optical projection system and exposed on holographic medium. In this paper we represent the research of holographic memory system based on computer generated Fourier holograms projection.