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Diffraction waveguides are widely used in augmented reality devices as information display systems for the introduction of data into the human visual field in order to supplement information about the world around us. This paper formulates the principles of radiation conversion in diffraction waveguides made of photo-thermo-refractive glass on the basis of multiplexed volume holographic gratings, and the advantages and disadvantages of high spectral-angular selectivity are analyzed. In the optical scheme, each of the superimposed volume holographic gratings in the diffraction waveguide forms a corresponding part of the composite angular field of view of the augmented reality device. A proposed mathematical model based on angular multiplexing made it possible to synthesize the diffraction optical element for a new type of diffraction waveguide made from photo-thermo-refractive glass and to create a prototype with an angular resolution of at least 3.0 ± 0.5′, with a brightness change in the image of less than 20% and with a composite angular field of view of 32°.

This paper describes the experiment on multiplexing recording using a phase mask to create augmented reality waveguides. The study is distinguished by the application of photo-thermo-refractive glass as both holographic and substrate materials. The presented approach allows us to obtain the diffraction efficiency above 15% in each of the multiplexed gratings for sevenfold recording. The images output with the manufactured planar waveguide prototype are presented.

Subjects were required to perform a horizontal reactive saccade towards a laterally misplaced cross. A photoimage of a human face with a basic emotional expression was flashed either perisaccadically or intrasaccadically, with a step size of 2 frames. A stably rising facial expression identification rate during the course of a saccade spanning 10 dva is shown. No evidence of a saccadic suppression with this type of stimulus is found, at least not for all of them. Performance metrics for identificaiton rate are reported. Possible unintended procedural artifacts are discussed. Spatial frequency analysis is held. Evidence for continuous, uninterrupted perceptive process during rapid eye movements is shown. Comparison with classic papers of 1970’s given. Interaction of luminance, spatial frequency, angular distance, chromaticity and angular size factors is suggested. It is shown that psychophysical (visual) features of the stimulus used are likely to be most predetermined for correct identification with given temporal (and functional) constraints. Shape of contour, spatial frequency distribution, skin texture and facial features, optimal angular size are yet to be determined, but evidence is shown that a special type of stimulus has to be developed and generated to control this issue.

Multiplexed volume holographic gratings are used as spectral and angular optical couplers for augmented reality displays and high-power laser applications. Paper presents modeling approach and recording experiments to create couplers in photo-thermo-refractive glass.

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.

In interference linear optical displacement sensors, precise position information is provided by the pair of quadrature sine and cosine signals while measuring scales moves along each other. One of these scales is a transmission diffraction grating that combines beam splitter function with phase retardation element. Precalculated parameters of that gratings based not only on diffraction efficiency analysis but phase relations in orders as well, helps to stabilize quadrature signals in the displacement sensor. This paper set the optimization condition in terms of phase shifts of light in diffraction orders influencing phase imbalance. To simulate the conversions of optical radiation by diffraction gratings, a rigorous coupled waves analysis was used. The phase imbalance of the obtained quadrature signals is estimated depending on the uncertainties of influencing parameters.

The article describes the variants for using the relief phase diffraction gratings for a waveguide used as an optical input/output element for images in augmented reality systems. A characteristic feature of diffraction gratings with a surface relief, which, in this case, were recorded in the photoresist layer, is a relatively small relief depth (of the order of several tenths of a micrometer), while the diffraction efficiency of such gratings is quite high (up to 30%). The paper considers an implementation option for a waveguide with a common angular field of view close to 60°. The article presents the waveguide options used to output both monochrome images and display full-color images.

This presentation is devoted to methods of multiplex volume Bragg diffraction gratings production. One of last developed and most promising volume photosensitive material of a such gratings is a photo-thermo-refractive glass. Low photosensitivity and high cost of suitable lasers for this material is a huge disadvantage. This makes traditional interference method of Brag gratins production difficult to implement. Thus a new method or a new vision of previous methods of a Bragg grating production required. A scheme of optical replication of easy-to-earn relief-phase grating into volume medium is considered. A mathematical modelling of interference field forming in volume medium during this process and attained diffraction efficiency of Bragg grating is performed. Experimental research at pulsed and CW lasers setups were carried out and achieved samples of multiplex Bragg grating described. A method of vibration-independent and low-sensitivity-material-suitable optical replication for production of multiplex volume Bragg gratings is described.

In interferential linear displacement sensors, accurate information about the position of the reading head is calculated out of a pair of quadrature (sine and cosine) signals. In double grating interference schemes, diffraction gratings combine the function of beam splitters and phase retardation devices. Specifically, the reference diffraction grating is located in the reading head and regulates the phase shifts in diffraction orders. Measurement diffraction grating moves along with the object and provides correspondence to the displacement coordinate. To stabilize the phase imbalance in the output quadrature signals of the sensor, we propose to calculate and optimize the parameters of these gratings, based not only on the energetic analysis, but along with phase relationships in diffraction orders. The optimization method is based on rigorous coupled-wave analysis simulation of the phase shifts of light in diffraction orders in the optical system. The phase properties of the reference diffraction grating in the interferential sensor are studied. It is confirmed that the possibility of quadrature modulation depends on parameters of static reference scale. The implemented optimization criteria are formulated in accordance with the signal generation process in the optical branch. Phase imbalance and amplification coefficients are derived from Heydemann elliptic correction and expressed through the diffraction efficiencies and phase retardations of the reference scale. The phase imbalance of the obtained quadrature signals is estimated in ellipticity correction terms depending on the uncertainties of influencing parameters.

The paper considers optical linear encoder based on diffraction gratings. A method of quadrature signals phase shift stabilization based on the application of head grating with specific structure is proposed. The optical scheme of position encoder based on measuring head grating with specific structure is developed and described in this paper. Mathematical modeling of quadrature signals phase shift depending on grating parameters is carried out. Based on the simulation, we propose optimal parameters of head grating structure. Design process and results for head gratings are presented in the paper.

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).

Linear displacement encoders are necessary in field of machine tools, metrology and electronic industry. Those devices provide nanometric resolution when constructed according to the interferometric scheme. Mathematical modeling of signal transfer process into its optical system to analyze an interference field is described. Signal intensity depending on a small displacement of moving grating phase shift correlations is considered. A sample model of the linear optical encoder is developed based on the optical scheme under research.

The paper describes a stable method for multiplexed recording of the Bragg diffraction gratings for waveguides using a phase mask. Diffraction waveguides in this experiment were made of photo-thermo-refractive glass. Two types of the phase mask are considered: surface and volume. Their comparison is based on diffraction characteristics of manufactured single and multiplexed Bragg gratings. The experimental results showed the advantage of surface phase mask application. To confirm the efficiency of the proposed method, diffraction waveguides was successfully fabricated and integrated in see-through near-eye display.

That paper focuses on indirect measurements of the diffraction gratings by analyzing their scattered distribution. The method is based on pre-calculated numerical dependencies of the energy characteristics. The comparison of measured diffraction efficiency values with numerical simulations provide the inverse measurements of the profile height. Presented research belongs to the field of scatterometry of high-resolution diffraction optical elements. The concept is tested with polymeric sinusoidal relief. Considered phase diffraction gratings have interest in field of linear displacement encoders.

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 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.

That paper focuses on diffraction gratings consisting some period failures provided by the errors of the electronbeam lithography method. Samples of lithographic phase gratings were tentatively analyzed to describe that technological errors. A small linear modulation of the period or a joint of a frame edges can cause not only diffraction efficiency losses but also functional breakdown. A simulation of the diffraction of a monochromatic wave at the described diffraction phase structures is carried out. Described diffraction gratings have interest in field of linear displacement encoders.

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.

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.

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.

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.

Optical head with magnetized garnet layer is used to detect presence of thin ferromagnetic layers such as printed text. Mathematical model of the system presented further was created. By varying opaque material, layer thicknesses and air gap between optical head and scanned object optimal configuration of the system was calculated. Incident P-polarized light affected by garnet layer changes its polarization due to Faraday effect. We can detect presence or absence of ferromagnetic after studying changes in polarization of the reflected light. Comparing results with and without influence of the ferromagnetic layers recognition of printed pattern under opaque material is achieved.

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.

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.

The fundamental methods for analyzing the parameters of diffraction gratings (DGs) are presented. The features of the application of DGs as measurement scales in a linear-displacement sensor system are analyzed. A method and quality criteria for monitoring the parameters of real samples of measurement scales are proposed. These criteria generalize all diffraction efficiencies that affect the formation of quadrature signals in the system of an interferometric linear-displacement sensor.

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.

Combined diffractive optical elements, which perform the functions of deflection, focusing or transformation of wave fronts and together with the spectral-angular selection of the incident polychromatic radiation, obtained on a single substrate, the method of their design and fabrication are described. The combination of four-level diffraction grating with plasmon meander diffraction grating as a spectral filter that have a bandwidth that varies with the angle of incidence are investigated for use in virtual displays and indicators.

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 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.

Security holograms (SH) are perspective for document and product authenticity protection 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 of automatic quality inspection of nickel master-matrix based on digital processing of its surface relief microphotographs. 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 SH master-matrices inspection are shown in this paper.

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.

An optical position encoder uses two difraction gratings in a measurement scale and measuring head for generating cosine measurment signals. This report is about special subperiod structuring of thees gratings for generating of two signals with quadrature phase shift for better the resolution of an optical position encoder.