Search

An augmented reality display based on a planar waveguide made in photo-thermo-refractive glass had been demonstrated. The monolithic integration of multiplexed volume Bragg gratings with the waveguide platform provided in/out-coupling and image transmission from a portable projector. Design and calculation of the grating configuration was performed. The optical replication method was simulated and implemented for manufacturing the multiplexed coupling elements. Resulted field of view was limited by the projection system of the prototype, however can be expanded beyond 50o.

The article describes the features of the security elements used in color three-dimensional security holograms. Unlike classical security holograms - "rainbow" relief - phase holograms, color three-dimensional security holograms have spectral and angular selectivity. This feature allows them to create new security elements or use the properties of already known elements as a new. The article describes the schemes and devices for creating such security elements, as well as devices for their visualization and control. Examples of typical security elements used in color three-dimensional security holograms are presented. This work was supported by the Russian Science Foundation (Project No. 18-79-00304).

The article presents a two-stage scheme for obtaining volume color security holographic stereograms. These holograms are digital holograms. The H1 - hologram is recorded at the first stage. The final holographic stereogram is recorded at the second stage. The image of the H1-hologram is reconstructed in the plane of pupils of the observer's eyes, when 3-D images are reconstructed from holographic stereograms. The quality of the 3-D images reconstructed from hologram stereograms directly depends on the degree of blurring of the H1 image - the hologram. The article shows mathematical calculations describing the effects of the spectral and angular selectivities of a three-dimensional color security holographic stereogram on the process of reconstructing 3-D images (the degree of blurring of the H1 image-hologram). It is shown, that the quality of security elements, such as the "flip-flop effect", for this type of hologram, has a more pronounced effect in the vertical plane than in the horizontal plane. This is due to the large influence of the spectral and angular selectivities in the vertical plane, than in the horizontal one when reconstructing the images. Photos of images, reconstructed from a three-dimensional color security holographic stereogram, are also presented in the article. These photos confirm the correctness of the presented calculations.

In this paper, dependencies of the angular and spectral selectivity on the incidence angle of the reference beam in a scheme for obtaining reflection and transmission holograms are obtained and analyzed. It is shown that for obtaining color holographic stereograms a scheme for obtaining transmission holograms is more suitable. While the angular selectivity of reflection and transmission color holograms is the same, the spectral selectivity of the reflection hologram is much higher at all wavelengths of recording. A method and equipment for one-step digital recording of color full-parallax holographic stereograms with rasterless image are developed. Samples of color full-parallax security holographic stereograms with a “flip-flop” effect in the image were obtained. The quality of the reconstructed image verifies high spectral selectivity for this type of holograms.

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 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 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.

A method of computer generation and projection recording of microholograms for holographic memory systems is presented; the results of mathematical modelling and experimental implementation of the method are demonstrated.

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.

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.

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.

Holographic screen (HS) is designed for using in 3D displays. HS is produced as a hologram of converging light wave and it presents an interference pattern of the reference and the object beams as a diffraction grating with variable pitch registered in the recording medium. While a color image is projected on such screen the problem of perception of the undistorted color image by the observer is appeared (due to the inherent angular dispersion of a grating with different values for different wavelengths) because the observation zones are displaced in space for each spectrum section. The problem is solved due to recording the HS by the object beam from the set of point sources, i.e. recording lengthy in the appropriate direction diffuser. With this type of HS, the observation zones, providing an undistorted perception of full-color images, are located in the imposition of lengthy images of projectors' pupils corresponding to different spectral components of projectors' radiation beams. To form an image, different projectors can be used in the display: slide projectors, video projectors based on LCD- or DMD-panels, etc. Three-dimensional images of both static and dynamic scenes can be viewed as video films at the appropriate information flows synchronization which are received by the projector from external sources.

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 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 observer's 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.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

This paper discusses questions associated with the fabrication of flat and spherical holographic mirrors intended to operate as part of the eyepiece system of night-vision glasses on a layer of dichromated gelatin. A method is proposed for recording holographic mirrors, and principles are proposed for calculating the parameters of the optical system of the apparatus for recording them. A process is presented, along with the results of work on the fabrication of holographic mirrors.

A microhologram-multiplexing method that makes it possible to increase the rate at which information is recorded and read out is proposed and investigated. An optical system for implementing the given method has been developed and experimentally tested. It is shown that holograms can be multiplexed by using a multichannel recording head, and that they can be read out simultaneously by using a multichannel readout head. The proposed multiplexing method and the optical system developed for creating archival optoholographic memory systems have the advantages that there is no need to mechanically displace the elements of the system during multiplexing at the recording stage nor during reconstruction of the multiplexed holograms, that there is no crosstalk in the beams reconstructed from the multiplexed holograms, and that relatively thin recording media can be used for recording.