Computer Optics

789-799

Authors: A.V. Volyar, Ya.E. Akimova

We investigated conditions for the violation of the structural stability of a spiral beam subject to sector perturbations. Based on the method of computer simulation and measurement of mode spectra, we have shown that a spiral vortex beam has a characteristic caustic surface, the intersection of which sharply changes the shape of the Poynting vector streamlines and the total topological charge of the beam. Sector beam perturbation does not almost change the streamline structure up to scale and rotation. We found that perturbation of the beam causes a change in the direction of circulation of streamlines in the region of perturbation, which is caused by the appearance of vortices with negative topological charges. Their contribution to the total energy flow is fractions of a percent. However, such perturbations do not cause changing the OAM in the beam, despite an increase in the number of vortex modes. Nevertheless, the perturbed beam remains only conditionally structurally stable due to the presence of a small fraction of optical currents with opposite circulations.

809-817

Authors: A.A. Kovalev, V.V. Kotlyar, D.S. Kalinkina, A.G. Nalimov

We discuss paraxial light beams composed of decentered Gaussian beams, with their phase selected in a special way so that their superposition is invariant as it propagates in free space, retaining its cross-section shape. By solving a system of five nonlinear equations, a superposition is constructed that forms an invariant off-axis elliptic Gaussian beam. An expression is obtained for the orbital angular momentum of this beam. It is shown that it consists of two components. The first of them is equal to the moment relative to the center of the beam and increases with increasing ellipticity. The second one quadratically depends on the distance from the center of mass to the optical axis (an analogue of Steiner's theorem). It is shown that the orientation of the ellipse in the transverse plane does not affect the normalized orbital angular momentum.

828-838

Authors: M.S. Gubaev, S.A. Degtyarev, Y.S. Strelkov, S.G. Volotovskiy, N.A. Ivliev, S.N. Khonina

We propose to use a refractive conical axicon for generating azimutally polarized beams. We investigate polarization states of optical rays passing through an interface between optical media, and also polarization transformation with a refractive axicon. We develop a software for raytracing which correctly processes polarization states of the rays and visualizes ellipses of polarization. The polarization state is described in the Jones notation and based on the energy conservation law. We derive and implement formulas for calculating the Jones vector in different bases, as well as trans-ferring the Jones vector from one basis to another. Algorithms for displaying polarization ellipses on one plane for beams that are not plane-parallel have been developed. Ray paths in a three-dimensional axicon are calculated and shown with due regard for polarization.

848-852

Authors: Y.E. Geints, O.V. Minin, I.V. Minin

We propose and discuss main properties of a new concept of an all-optical dielectric two-channel wavelength-selective switch based on the photonic hook effect. A prototype of such a de-vice based on dielectric microstructures with broken symmetry of both geometric shape and optical properties without the use of micromechanical devices or nonlinear materials is considered. Due to the unique property of the photonic hook to change its curvature depending on the wavelength of illuminating light, this switch is a promising candidate for the implementation of optical switching in modern optoelectronics and miniature devices "on a chip". Based on numerical FDTD simulations, it is shown that the optical isolation of switched channels for a switch with linear dimensions of about (6 * "lambda")3 based on a Janus particle can reach about 18-20 dB in the wavelength range of 1.5 – 1.9 microns.

860-864

Authors: M.S. Komlenok, O.S. Kudryavtsev, D.G. Pasternak, I.I. Vlasov, V.I. Konov

A possibility of laser printing of single diamond nanoparticles with luminescent SiV centers is demonstrated. To provide the transfer, a target consisting of a transparent sapphire plate and an absorbing thin titanium film (600 nm thick) coated with nanoparticles was irradiated with a KrF excimer laser ("lambda"=248 nm, "tau"=20 ns). Optimal values of the laser fluence have been determined and a technique for applying labels for the targeted transfer of nanoparticles has been developed. Luminescence mapping of the donor and the receiving substrates confirmed the transfer of diamond nanoparticles with SiV centers.

873-878

Authors: R.A. Paringer, A.V. Mukhin, A.V. Kupriyanov

The paper is about the development of an approach which able to create rules for distinguish-ing between specified objects of hyperspectral data using a small number of observations. Such an approach would contribute to the development of methods and algorithms for the operational analysis of hyperspectral data. These methods can be used for hyperspectral data preprocessing and labeling. Implementation of the proposed approach are using a technology that harnesses both discriminative criteria and the general formulas of spectral indexes. In implementing the proposed technology, the index was defined with normalized difference formula. The Informativeness was estimated using separability criteria of discriminative analysis. The results show that the implemented algorithm can recognize areas of hyperspectral data with different vegetation. The index formed by the algorithm is similar to Normalized Difference Vegetation Index (NDVI). The proposed technology is the generalization of the approach of forming recognition rules using a small number of features. It has been shown that technology can form informative indexes in specified tasks of hyperspectral data analysis.

887-896

Authors: N. Firsov, V. Podlipnov, N. Ivliev, P. Nikolaev, S. Mashkov, P. Ishkin, R. Skidanov, A. Nikonorov

In this paper, we propose an approach to the classification of high-resolution hyperspectral images in the applied problem of identification of vegetation types. A modified spectral-spatial convolutional neural network with compensation for illumination variations is used as a classifier. For generating a training dataset, an algorithm based on an adaptive vegetation index is proposed. The effectiveness of the proposed approach is shown on the basis of survey data of agricultural lands obtained from a compact hyperspectral camera developed in-house.

907-916

Authors: I.A. Kanaeva, Yu.A. Ivanova, V.G. Spitsyn

We discuss a range of problems relating to road pavement defects detection and modern approaches to their solution. The presented comparison of publicly available datasets allows one to make a conclusion that the problem of segmentation of road pavement defects in driver wide-view road images is difficult and poorly investigated. To solve this problem, we have developed algorithms for generating a synthetic dataset for cracks and potholes distress based on computer graphics methods and deep convolutional generative adversarial networks. A comparison of the accuracy of road distress segmentation was performed by training a fully convolutional neural network U-Net on real and combined datasets.

926-933

Authors: I.V. Zenkov, A.V. Lapko, V.A. Lapko, E.V. Kiryushina, V.N. Vokin, A.V. Bakhtina

We study in which way a priori information on the independence of random variables affects the approximation accuracy of a nonparametric estimate of the Rosenblatt–Parzen probability density. A new technique for generating sets of independent components of a multidimensional random variable is proposed. The methodology is based on testing the hypotheses of the independence of combinations of the multidimensional random variable components using a two-alternative nonparametric kernel algorithm for pattern recognition corresponding to the maximum likelihood criterion. Classes correspond to the domains of definition of the probability densities of sets of independent and dependent components of the multidimensional random variable. Nonparametric statistics of the kernel type are used to estimate the probability densities. The choice of the bandwidths of the kernel estimates of the probability densities is made from the condition of the minimum root-mean-square criterion. The sequential procedure for generating a set of independent components begins with the analysis of paired combinations of components of a multidimensional random variable. For each pair of components, the probability of an error in recognizing classes corresponding to the assumptions of independence and dependence of the considered components is estimated. A pair of components with the maximum difference between these errors is determined. If the errors obtained do not differ significantly, then there are no independent components in the considered multivariate random variable. If there is a significant difference in the probability estimates of class recognition errors, a pair of independent components is established. These components are included in a three-component set of a multidimensional random variable. The analysis of their combinations is carried out in the same way, following the above-described procedure. The process of generating the set of independent components is stopped when no reliable difference occurs any more between the probabilities of errors in recognizing situations belonging to the accepted classes. In this case, the previous set of independent components is the desired result. In contrast to the traditional methodology based on the Pearson criterion, the proposed approach allows us to bypass a problem of the decomposition of the range of values of random variables into multidimensional intervals. The method of generating a set of independent components of a multidimensional random variable is illustrated by the results of the analysis of spectral features of remote sensing data of forest tracts using space imagery from the Landsat-8 satellite.

643-653

Authors: V.V. Kotlyar, A.G. Nalimov, S.S. Stafeev, A.A. Kovalev

It is theoretically and numerically shown that when tightly focusing an n-th order vector light field that has the central V-point (at which the linear polarization direction is undetermined), the polarization singularity index n, and a "flower"-shaped intensity pattern with 2(n-1) lobes it forms a transverse intensity distribution with 2(n-1) local maxima. At the same time, a vector light field with the polarization singularity index -n, which has the form of a "web" with 2(n+1) cells generates at the sharp focus a transverse intensity distribution with 2(n+1) local maxima. In the focal spot, either 2(n-1) or 2(n+1) V-point polarization singularities with alternating indices +1 or -1 are formed at the intensity zero.

661-666

Authors: E.A. Bibikova, N.D. Kundikova, A.A. Shulginov, N. Al-Wassiti

The spin angular momentum and the extrinsic orbital angular momentum of light are associated with the polarization of light and the light propagation trajectory, respectively. Those momenta are interdependent not only in an inhomogeneous or anisotropic medium but even in free space. This interaction is called the spin-orbit interaction of light. The effects of the spin-orbit interaction of light manifest themselves in a small transverse shift of the beam field longitudinal component from the beam propagation axis in the waist region under the circular polarization sign change. They can be observed both for Gaussian beams and for structured beams. The effects of the spin-orbit interaction of light should be taken into account when nanophotonics devices are created, but the detailed investigation of the effect had not been performed yet due to the low intensity noise image of the beam waist. Precise measurements of the focal waist centerline are needed to determine the transverse shift of the beam field longitudinal component of the asymmetric converging beam's waist under the circular polarization sign change. We propose methods for determining the transverse and longitudinal positions of the beam waist. Computer image processing methods made it possible to obtain the value of the beam waist's transverse position with an accuracy of 0.1 mkm. These methods will allow further testing of the shifts' theoretical predictions, the values of which are the order of 1 mkm. The results obtained can also be used for laser processing of materials by polarized light and precise positioning of the beam's focal spot at a surface.

673-677

Authors: V.S. Pavelyev, K.N. Tukmakov, A.S. Reshetnikov, V.V. Gerasimov, N.D. Osintseva, B.A. Knyazev

Experimental results of the investigation of self-healing properties of terahertz Bessel beams with orbital angular momentum (OAM) with topological charges of l=3 and l=4 in free space after passing through a dispersive medium are presented.

685-691

Authors: S.S. Stafeev, V.D. Zaicev

It is shown theoretically and numerically that circularly and linearly polarized incident beams produce at the tight focus identical circularly symmetric distributions of an on-axis energy flux. It is also shown that the on-axis energy fluxes from radially and azimuthally polarized optical vortices with unit topological charge are equal to each other. An optical vortex with azimuthal polarization is found to generate the minimum focal spot measured for the intensity (all other parameters being equal). Slightly larger (by a fraction of a percent) is the spot size calculated for the energy flux for the circularly and linearly polarized light. The spot size in terms of intensity is of importance in light-matter interaction, whereas the spot size in terms of energy flux affects the resolution in optical microscopy.

702-712

Authors: D.V. Tropin, A.M. Ershov, D.P. Nikolaev, V.V. Arlazarov

The demand for on-device document recognition systems increases in conjunction with the emergence of more strict privacy and security requirements. In such systems, there is no data transfer from the end device to a third-party information processing servers. The response time is vital to the user experience of on-device document recognition. Combined with the unavailability of discrete GPUs, powerful CPUs, or a large RAM capacity on consumer-grade end devices such as smartphones, the time limitations put significant constraints on the computational complexity of the applied algorithms for on-device execution. In this work, we consider document location in an image without prior knowledge of the document content or its internal structure. In accordance with the published works, at least 5 systems offer solutions for on-device document location. All these systems use a location method which can be considered Hough-based. The precision of such systems seems to be lower than that of the state-of-the-art solutions which were not designed to account for the limited computational resources. We propose an advanced Hough-based method. In contrast with other approaches, it accounts for the geometric invariants of the central projection model and combines both edge and color features for document boundary detection. The proposed method allowed for the second best result for SmartDoc dataset in terms of precision, surpassed by U-net like neural network. When evaluated on a more challenging MIDV-500 dataset, the proposed algorithm guaranteed the best precision compared to published methods. Our method retained the applicability to on-device computations.

721-727

Authors: A.D. Fida, A.V. Gaidel, N.S. Demin, N.Yu. Ilyasova, E.A. Zamytskiy

We discuss approaches to combining multimodal multidimensional images, namely, three-dimensional optical coherence tomography (OCT) data and two-dimensional color images of the fundus. Registration of these two modalities can help to adjust the position of the obtained OCT images on the retina. Some existing approaches to matching fundus images are based on finding key points that are considered invariant to affine transformations and are common to the two images. However, errors in the identification of such points can lead to registration errors. There are also methods for iterative adjustment of conversion parameters, but they are based on some manual settings. In this paper, we propose a method based on a full or partial search of possible combinations of the OCT image transformation to find the best approximation of the true transformation. The best approximation is determined using a measure of comparison of preprocessed image pixels. Further, the obtained transformations are compared with the available true transformations to assess the quality of the algorithm. The structure of the work includes: pre-processing of OCT and fundus images with the extraction of blood vessels, random search or grid search over possible transformation parameters (shift, rotation and scaling), and evaluation of the quality of the algorithm.

736-748

Authors: A.S. Konushin, B.V. Faizov, V.I. Shakhuro

Traffic sign recognition is a well-researched problem in computer vision. However, the state of the art methods works only for frequent sign classes, which are well represented in training datasets. We consider the task of rare traffic sign detection and classification. We aim to solve that problem by using synthetic training data. Such training data is obtained by embedding synthetic images of signs in the real photos. We propose three methods for making synthetic signs consistent with a scene in appearance. These methods are based on modern generative adversarial network (GAN) architectures. Our proposed methods allow realistic embedding of rare traffic sign classes that are absent in the training set. We adapt a variational autoencoder for sampling plausible locations of new traffic signs in images. We demonstrate that using a mixture of our synthetic data with real data improves the accuracy of both classifier and detector.

756-766

Authors: Yu.V. Vizilter, O.V. Vygolov, S.Yu. Zheltov

We introduce attribute and relational representations of mosaic image models with directed relationships between regions. Attribute representations of asymmetric relational models based on stacking, ranking and integral descriptions are considered. We propose some morphological shape similarity measures based on relational models. We show that using the same oriented relational model, various morphological operators can be constructed, in particular, of Serra- or Pyt’ev type. Some constructive methods for the design of such morphological operators in an attribute and relational domains are proposed. From this consideration we also extract a new morophlogical scheme for two-stage mutual adaptive image-and-shape joint filtering: at the first step, the shape is simplified (projected) with regard to the image to be projected, and at the second step, the image is simplified (projected) with regard to the simplified (projected) shape.

773-778

Authors: A.S. Mokeev, V.M. Yamshchikov

We discuss features of the calculation of a Fraunhofer integral by traditional quadrature numerical integration methods and a special collocation Levin method when calculating the diffraction of a plane electromagnetic wave by a rectangular aperture. For the quadrature numerical integration methods, a criterion for the assessment of the integration step is derived depending on the screen size and required calculation accuracy. Advantages of the use of the special collocation Levin method in comparison with the traditional quadrature numerical integration methods are shown.

475-481

Authors: Editorial

Вы держите в руках или просматриваете на сайте 100-й выпуск журнала «Компьютерная оптика». Начав издаваться 34 года назад, с 1987 года, журнал прошёл плодотворный путь в своём становлении как ведущее международное научное издание, привлекающее внимание не только отечественных специалистов, но и ученых со всех уголков планеты. Из научного сборника с периодичностью 1 – 2 выпуска в год издание в 2007 году выросло до регулярного журнала с 4-мя, а начиная с 2016 года – 6-ю номерами в год, в которых ежегодно публикуется более 120 статей.

490-496

Authors: V.V. Kotlyar

In optical data transmission with using vortex laser beams, data can be encoded by the topo-logical charge, which is theoretically unlimited. However, the topological charge of a single sepa-rate vortex is limited by possibilities of its generating. Therefore, in this work, we analyze light beams with an unbounded (countable) set of optical vortices. The summary topological charge of such beams is infinite. Phase singularities (isolated intensity nulls) in such beams typically have a unit topological charge and reside equidistantly (or not equidistantly) on a straight line in the beam cross section. Such beams are form-invariant and, on propagation in space, change only in scale and rotate. Orbital angular momentum of such multivortex beams is finite, since only a finite number of optical vortices fall into the area, where the Gaussian beam has a notable intensity. Other phase singularities are located in the periphery (and at the infinity), where the intensity is almost zero.

506-511

Authors: V.V. Kotlyar, A.A. Kovalev, D.S. Kalinkina, E.S. Kozlova

In this paper, we consider a new type of Bessel beams having Fourier-invariance property and, therefore, called Fourier-Bessel beams. In contrast to the known Bessel beams, these beams have weak side lobes. Analytical expressions for the complex amplitude of the proposed field in the initial plane of the source and in the far field region have been obtained. It is shown that the proposed Fourier-Bessel beams have a finite energy, although they do not have a Gaussian envelope. Their complex amplitude is proportional to a fractional-order Bessel function (an odd integer divided by 6) in the initial plane and in the Fraunhofer zone. The Fourier-Bessel modes have a smaller internal dark spot compared to the Laguerre-Gauss modes with a zero radial index. The proposed beams can be generated with a spatial light modulator and may find uses in telecommunications, interferometry, and the capture of metal microparticles.

520-524

Authors: S.S. Stafeev

We have shown that a reverse energy flow (negative projection of the Poynting vector onto the optical axis) at the sharp focus of an optical vortex with topological charge 2 and left-hand circular polarization arises because the axial spin flow has a negative projection onto the optical axis and is greater in magnitude than positive projection onto the optical axis of the orbital energy flow (canonical energy flow). Also, using the Richards-Wolf formulas, it is shown that when focusing a left-handed circularly polarized light, in the region of the on-axis reverse energy flow, the light is right-handed circularly polarized.

534-540

Authors: J.D. Arango, Y.A. Vélez, V.H. Aristizabal, F.J. Vélez, J.A. Gómez, J.C. Quijano, J. Herrera-Ramirez

The response of fiber specklegram sensors (FSSs) is given as function of variations in the intensity distribution of the modal interference pattern or speckle pattern induced by external disturbances. In the present work, the behavior of a FSS sensing scheme under thermal perturbations is studied by means of computational simulations of the speckle patterns. These simulations are generated by applying the finite element method (FEM) to the modal interference in optical fibers as a function of the thermal disturbance and the length of the sensing zone. A correlation analysis is performed on the images generated in the simulations to evaluate the dependence between the changes in the speckle pattern grains and the intensity of the applied disturbance. The numerical simulation shows how the building characteristic of the length of sensing zone, combined with image processing, can be manipulated to control the metrological performance of the sensors.

551-561

Authors: A.V. Pavlov

The article is dedicated to the search for a biologically motivated mechanism of the cognitive phenomenon of violation of the classical formula of total probability for the disjunction of incompatible events, which is considered by a number of researchers as a quantum-like phenomenon. A classical mechanism implemented by the 6f Fourier holography scheme of the resonant architecture that does not require reference to quantum mechanics either in its physical nature or at the level of formalism is demonstrated. In the analysis, the decision-making is interpreted as a choice of alternatives by using the non-cooperative game "Prisoner's Dilemma". The approach to the task is based on the search for a mechanism for forming a conditional estimate under a condition that contradicts the rule of monotonous decision logic. It is demonstrated that this estimate, in contrast to the unconditional and conditional one with a non-contradictory condition, is formed by logic with exception. The ring architecture of the holographic setup corresponds to the biologically inspired neural network concept of the excitation ring and implements cognitive dissonance on logic with exception. Conditions and ranges of violation of the classical formula of total probability in relation to the correlation radius of the reference image recorded in a hologram storing the monotone logic inference rule are analytically determined. The analytical model is confirmed by a quantitative coincidence of the results of numerical modeling with the published results of natural experiments.

575-579

Authors: D.A. Gavrilov

The paper investigates the applicability of the convolutional neural network "U-Net" to a problem of segmentation of aircraft images. The neural network image segmentation method is based on the "Carvana" implementation with the "U-Net" architecture. For orientation recognition, a neural network built in the Keras open neural network library based on the pretrained VGG16 neural network is used. The approach considered allows the image segmentation to be conducted. The results of the experiments have shown the possibility of a fairly accurate selection of the object of interest. The resulting binary masks make it possible to visually classify the aircraft in the image.

589-599

Authors: I.A. Kudinov, M.B. Nikiforov, I.S. Kholopov

We derive analytical expressions for calculating the number of elementary computational operations required to generate several personal regions of interest in a panoramic computer-vision distributed-aperture system using two alternative strategies: strategy 1 involves acquisition of a complete panoramic frame, followed by the selection of personal regions of interest, while with strategy 2 the region of interest is directly formed for each user. The parameters of analytical expressions include the number of cameras in the distributed system, the number of users, and the resolution of panorama and user frames. The formulas obtained for the given parameters make it possible to determine a strategy that would be optimal in terms of a criterion of the minimum number of elementary computational operations for generating multiple personal regions of interest. The region of interest is generated using only a priori information about the internal and external camera parameters, obtained as a result of their photogrammetric calibration with a universal test object, and does not take into account information about scene correspondences at the boundaries of intersecting fields of view.

608-614

Authors: A.V. Uzhinskiy, G.A. Ososkov, P.V. Goncharov, A.V. Nechaevskiy, A.A. Smetanin

Triplet loss function is one of the options that can significantly improve the accuracy of the One-shot Learning tasks. Starting from 2015, many projects use Siamese networks and this kind of loss for face recognition and object classification. In our research, we focused on two tasks related to vegetation. The first one is plant disease detection on 25 classes of five crops (grape, cotton, wheat, cucumbers, and corn). This task is motivated because harvest losses due to diseases is a serious problem for both large farming structures and rural families. The second task is the identification of moss species (5 classes). Mosses are natural bioaccumulators of pollutants; therefore, they are used in environmental monitoring programs. The identification of moss species is an important step in the sample preprocessing. In both tasks, we used self-collected image databases. We tried several deep learning architectures and approaches. Our Siamese network architecture with a triplet loss function and MobileNetV2 as a base network showed the most impressive results in both above-mentioned tasks. The average accuracy for plant disease detection amounted to over 97.8% and 97.6% for moss species classification.

627-637

Authors: V.V. Syuzev, E.V. Smirnova, A.V. Proletarsky

The article discusses two approaches to modeling signals and processes: the method of filter construction and the trigonometric method. It is shown that the later approach is more promising, since an increase in the signal/process representation dimension mathematically means adding a term to the basis function formula, which gives access to fast simulation algorithms. Examples of algorithms for multidimensional simulation of random processes using two methods are given and a software system that implements these algorithms is described. The results provided by the software system will allow you to predict characteristics of engineering projects (accuracy and speed of modeling algorithms). Due to the high relevance of and need for fundamental research of methods and algorithms for digital transformation of the component base, the digitalization of all aspects of activity, including the synthesis of new materials, the development of new methods for designing micro- and nano-systems, the article aims to expand the scope of the spectral method of simulating multidimensional processes using original algorithmic complexes.

311-318

Authors: V.V. Kotlyar, S.S. Stafeev

Tight focusing of light with mth-order circular-azimuthal polarization was investigated. This is a new type of inhomogeneous hybrid polarization that combines the properties of mth order cylindrical polarization and circular polarization. Using the Richards-Wolf formalism, we obtained analytical expressions in the focal spot for the projections of the electric and magnetic field, the intensity distribution, the projections of the Poynting vector, and the spin angular momentum. It was shown theoretically and numerically that at the focus, the intensity has 2(m+1) local maxima located on a circle centered on an on-axis intensity null. It was shown that 4m vortices of a transverse energy flow were produced at the focus, with their centers located between the local intensity maxima. It was also shown that in the focal plane, the transverse energy flow changes the direction of rotation 2(2m+1) times around the optical axis. It is interesting that the longitudinal projection of the spin angular momentum at the focus changes sign 4m times. In those areas of the focal plane where the transverse energy flow rotates counterclockwise, the longitudinal projection of the spin angular momentum is positive, and the polarization vector rotates counterclockwise in the focal plane. Conversely, if the energy flow rotates clockwise, the polarization vector rotates clockwise, and the longitudinal projection of the spin angular momentum is negative. Numerical simulations are in agreement with the theoretical investigation.

324-330

Authors: R.V. Kutluyarov, D.M. Fatkhiev, I.V. Stepanov, E.P. Grakhova, V.S. Lyubopytov, A.K. Sultanov

We propose and numerically verify a design of the photonic integrated circuit for in-plane generation of a 1st azimuthal order vortex mode in dielectric rectangular waveguides. Radiation is introduced into the proposed structure in a standard way through two grating couplers. Applying a mode coupling and specific phase shift, a field with the required amplitude-phase distribution is formed directly in the output waveguide. The geometric dimensions of the device are simulated and optimized to fit the technological parameters of the silicon-on-insulator platform.

340-349

Authors: D.V. Lyakin, V.P. Ryabukho

The effect of the width of the angular spectrum (numerical aperture) of a broadband-frequency wave-field probing a layered object on the signal of an autocorrelation low-coherence interferometer (ALCI) under spatially coherent and incoherent illumination of the entrance pupil is considered. It is found that under incoherent illumination an increase in the width of the angular spectrum of the field leads to a decrease in the amplitude, a change in the shape and position of the measuring signals of the interferometer due to decorrelation of the object field partial components which have reflected from various interlayer boundaries inside the object. In the case of coherent illumination, the ALCI signal is formed in a confocal mode, which leads to the amplitude extraction of the measurement signals are determined by the mutual correlations between a partial component reflected from the boundary on which the probing field was focused, and partial components of this field which have reflected from other boundaries within the object. This effect makes it possible to determine parameters of the internal layered structure of an object doing without apriori structure-related information. In this case, an increase in the numerical aperture of the probing light beam leads to an increase in the systematic error in determining the optical thicknesses of the layers, which can be estimated on the basis of the obtained expressions.

356-363

Authors: A.I. Kashapov, L.L. Doskolovich, D.A. Bykov, E.A. Bezus, D.V. Nesterenko

Optical properties of a resonant trilayer metal-dielectric-metal (MDM) structure that consists of an upper metal layer, a dielectric layer, and a metal substrate are investigated. Using a multiple wave interference model, we prove that the reflection coefficient of the MDM structure may strictly vanish. The existence of a reflectance zero makes it possible to use the MDM structure as an optical differentiator. The numerical simulation results presented demonstrate the possibility of optical computation of the first derivative with respect to either time or spatial variable. The obtained results may find application in novel analog optical computing and optical information processing systems.

372-381

Authors: V.A. Mikhailov, N.V. Troshkin

In this paper we investigate non-Markovian evolution of a two-level system (qubit) in a bosonic bath under influence of an external classical fluctuating environment. The interaction with the bath has the Lorentzian spectral density, and the fluctuating environment (stochastic field) is represented by a set of Ornstein-Uhlenbeck processes. Each of the subenvironments of the composite environment is able to induce non-Markovian dynamics of the two-level system. By means of the numerically exact method of hierarchical equations of motion, we study steady states of the two-level system, evolution of the reduced density matrix and the equilibrium emission spectra in dependence on the frequency cutoffs and the coupling strengths of the subenvironments. Additionally, we investigate the impact of the rotating wave approximation (RWA) for the interaction with the bath on accuracy of the results.

394-398

Authors: A.V. Demin, E.N. Sechak, S.P. Prisyazhnyuk

The article presents results of the development and research of a hyperspectral imaging spectrometer for analyzing borehole fluids in real operating conditions in the spectral range from 0.35 microns to 2.1 microns. A mathematical model and an algorithm for identifying the borehole fluid by composition and percentage content based on the results of hyperspectral image analysis are developed.

405-417

Authors: S. Madenda, A. Darmayantie

This paper describes the use of some color spaces in JPEG image compression algorithm and their impact in terms of image quality and compression ratio, and then proposes adaptive color space models (ACSM) to improve the performance of lossy image compression algorithm. The proposed ACSM consists of, dominant color analysis algorithm and YCoCg color space family. The YCoCg color space family is composed of three color spaces, which are YCcCr, YCpCg and YCyCb. The dominant colors analysis algorithm is developed which enables to automatically select one of the three color space models based on the suitability of the dominant colors contained in an image. The experimental results using sixty test images, which have varying colors, shapes and textures, show that the proposed adaptive color space model provides improved performance of 3 % to 10 % better than YCbCr, YDbDr, YCoCg and YCgCo-R color spaces family. In addition, the YCoCg color space family is a discrete transformation so its digital electronic implementation requires only two adders and two subtractors, both for forward and inverse conversions.

427-437

Authors: A.S. Shirokanev, N.A. Andriyanov, N.Y. Ilyasova

For diabetic retinopathy treatment, laser coagulation is used in modern practice. During the laser surgery process, the parameters of laser exposure are selected manually by a doctor, which requires the doctor to have sufficient experience and knowledge to achieve a therapeutic effect. On the basis of mathematical modeling of the laser coagulation process, it is possible to estimate the crucial parameters without performing an operation. However, the retina has a rather complex structure, and when even low-cost numerical methods are used for modeling, it takes a long time to obtain a result. In this regard, the development of time-efficient algorithms for three-dimensional modeling is an urgent task, since the use of such algorithms will provide a compre-hensive study within a limited time. In this paper, we study the execution time of algorithms that implement various variations in the application of the splitting method and the finite difference method, adapted to the set problem of heat conduction. The study reveals the most efficient algorithm, which is then vectorized and implemented using the CUDA technology. The study was carried out using Intel Core i7-10875H and Nvidia RTX 2080 MAX Q and showed that an analog of the vector algorithm, focused on solving a multidimensional heat conduction problem, provides an acceleration of no more than 1.5 times compared to the sequential version. The developed vector-based algorithm, focused on the application of the sweep method in all directions of the three-dimensional problem, significantly reduces the time spent on copying into the memory of the video card and provides a 40-fold acceleration in comparison with the sequential three-dimensional modeling algorithm. On the basis of the same approach, a parallel algorithm of mathematical modeling was developed, which provided a 20-fold acceleration at full processor load.

449-460

Authors: Y.V. Vizilter, O.V. Vygolov, S.Y. Zheltov

We consider the statistical properties of different mosaic filters. We demonstrate that in Pitiev's morphology, the measure of shape complexity is directly related to the shape simplicity measure based on morphological correlation coefficient (MCC). Based on MCC, we introduce the normalized morphological simplification index (NMSI). Using NMSI, we show that the simpler the mosaic shape, the more shape simplification is provided by the corresponding Pyt'ev projector. For the examples of mean and median mosaic filters, we address the problem of different operator comparison. In this context we introduce the concept of statistically simplifying morphological operators. Morphological correlation of mosaic shape and diffusion mosaic operator is considered. We prove that the NMSI for the diffusion mosaic operator is not related to the complexity for the corresponding diffusion shape kernel. Thus, a principal qualitative difference in the relationship between relational and operator models for diffuse and projective mosaic linear filters is demonstrated.

165-171

Authors: E.S. Kozlova, S.S. Stafeev, S.A. Fomchenkov, V.V. Podlipnov, V.V. Kotlyar

In this paper, an effect of a reverse energy flow at the focus of a second-order cylindrical vector beam which passed through amplitude zone plate was investigated with a scanning near-field optical microscope. A comparison of the intensity distribution detected with a pyramidal metallized cantilever with a hole and the characteristics of the light field calculated using a FDTD method and the Richards-Wolf formulas suggests that the cantilever is sensitive to the transverse intensity component rather than the total intensity or the components of the Poynting vector in the backflow region.

179-189

Authors: A.V. Volyar, M.V. Bretsko, Y.E. Akimova, Y.A. Egorov

A process of mode matching in a chaotic speckle pattern without a reference beam responsible for the formation of a holographic grating was studied experimentally and theoretically. Our approach was based on measuring the amplitudes and phases of the Hermite-Gauss (HG) and Laguerre-Gauss (LG) modes in a speckle pattern formed by the radiation of a multimode gradient fiber. The speckle pattern was formed in a hologram of a spatial light modulator using a multimode gradient fiber model while taking into account the mode and polarization dispersion, as well as random phase jumps of each eigenmode. We managed to match 210 modes of the speckle pattern and restore not only the original pattern, but also each structured LG mode and the entire chain of HG eigenmodes.

200-207

Authors: C.N. Alexeyev, E.V. Barshak, D.V. Vikulin, B.P. Lapin, M.A. Yavorsrky

In this paper we have demonstrated the emergence of an effective circular dichroism for the fundamental mode in fiber resonators of loop and ring types with an optically active element embedded into the loop/ring. Changing the parameters of the resonator, the optically active element, or the wavelength of the incoming field allows one to control the value of the effective dichroism and actually, to increase optical activity of the element. It is shown that these resonators can be used as working elements of all-fiber polarizers for the fundamental mode.

214-221

Authors: D.A. Savelyev

Spatial intensity distributions of the Laguerre-superGauss modes (1,0) as well as a super-Gaussian beam with radial and circular polarization were investigated versus changes in the height of a diffractive axicon. The height of the relief of the optical element varied from 0.25λ to 3λ. The modeling by a finite-difference time-domain method showed that variations in the height of the diffractive axicon significantly affect the diffraction pattern in the near field of the axicon. The smallest focal spot size for a super-Gaussian beam was obtained for radial polarization at a height equal to two wavelengths. The minimum size of the focal spot for the Laguerre-superGauss mode (1,0) was obtained for circular "–" polarization with an element height equal to a quarter of the wavelength.

227-234

Authors: L.M. Wisudawati S. Madenda, E.P. Wibowo, A.A. Abdullah

Breast cancer is a leading cause of death in women due to cancer. According to WHO in 2018, it is estimated that 627.000 women died from breast cancer, that is approximately 15 % of all cancer deaths among women [3]. Early detection is a very important factor to reduce mortality by 25-30 %. Mammography is the most commonly used technique in detecting breast cancer using a low-dose X-ray system in the examination of breast tissue that can reduce false positives. A Computer-Aided Detection (CAD) system has been developed to effectively assist radiologists in detecting masses on mammograms that indicate the presence of breast tumors. The type of abnormality in mammogram images can be seen from the presence of microcalcifications and the presence of mass lesions. In this research, a new approach was developed to improve the performance of CAD System for classifying benign and malignant tumors. Areas suspected of being masses (RoI) in mammogram images were detected using an adaptive thresholding method and mathematical morphological operations. Wavelet decomposition is performed on the Region of Interest (RoI) and the feature extraction process is performed using a GLCM method with 4 statistical features, namely, contrast, correlation, entropy, and homogeneity. Classification of benign and malignant tumors using the MIAS database provided an accuracy of 95.83 % with a sensitivity of 95.23 % and a specificity of 96.49 %. A comparison with other methods illustrates that the proposed method provides better performance.

245-252

Authors: E.A. Terekhin

The paper presents results of the analysis of long-term changes in the vegetation cover of abandoned agricultural lands in the forest-steppe zone of the Central Chernozem Region using time series of the Normalized Difference Vegetation Index (NDVI), which are measured using MOD13Q1 data. The vegetation index dynamics linked with the proportion of forest communities formed on the abandoned agricultural lands is investigated. The index values for the period of mid-August are the most informative for analyzing the share of forest communities growing on the abandoned agricultural land. Abandoned agricultural lands with coniferous forests have a higher correlation with NDVI than fallows with deciduous species. In the period 2000-2018, for all types of abandoned arable lands, the presence of a positive statistically significant trend component of the vegetation index long-term series is established. Using a slope angle coefficient of the NDVI trend line, a spatio-temporal analysis of the rate of formation of forest stands in the forest-steppe fallows at the beginning of the XXI century was carried out. Features of this process are studied.

261-266

Authors: A.A. Sludnova, V.V. Shutko, A.V. Gaidel, P.M. Zelter, A.V. Kapishnikov, A.V. Nikonorov

This article discusses an idea of a joint analysis of medical images and texts aimed at improving the quality of automated diagnosis of emphysema. We compare the quality of image classification with and without taking into account the localization of the pathology mentioned in radiological reports. The study was carried out on sets of real images of computed tomography of the lungs obtained in clinical studies at Samara State Medical University. It was established that the use of information on the localization of pathology contained in radiological reports leads to an increase in the F-score for the detection from 0.55 to 0.73.

277-285

Authors: A.V. Astafiev, D.V. Titov, A.L. Zhiznyakov, A.A. Demidov

The paper considers the development of a method for positioning a mobile device using a sensor network of BLE-beacons, the approximation of RSSI values and artificial neural networks. The aim of the work is to develop a method for positioning small-scale industrial mechanization equipment for building unmanned systems for product movement tracking. The work is divided into four main parts: data synthesis, signal filtering, selection of BLE beacons, translation of the RSSI values into a distance, and multilateration. A simplified Kalman filter is proposed for filtering the input signal to suppress Gaussian noise. A description of two approaches to translating the RSSI value into a distance is given: an exponential approximation function with a coefficient of determination of 0.6994 and an artificial feedforward neural network. A comparison of the results of these approaches is carried out on several test samples: a training one, a test sample at a known distance (0–50 meters) and a test sample at an unknown distance (60–100 meters). The artificial neural network is shown to perform better in all experiments, except for the test sample at a known distance (0–50 meters), for which the r.m.s. error is higher by 0.02 m 2 than that for the approximation function, which can be neglected. An algorithm for positioning a mobile device based on the multilateration method is proposed. Experimental studies of the developed method have shown that the positioning error does not exceed 0.9 meters in a 5×5.5 m room under monitoring. The positioning accuracy of a mobile device using the proposed method in the experiment is 40.9 % higher. Experimental studies are also conducted in a 58.4×4.5 m room, showing more accurate results compared to similar studies.

296-300

Authors: M. Liu, Z.H. Sun

With the development of computer technology, there are more and more algorithms and models for data processing and analysis, which brings a new direction to radar target recognition. This study mainly analyzed the recognition of high resolution range profile (HRRP) in radar target recognition and applied the generalized regression neural network (GRNN) model for HRRP recognition. In order to improve the performance of HRRP, the fruit fly optimization algorithm (FOA) algorithm was improved to optimize the parameters of the GRNN model. Simulation experiments were carried out on three types of aircraft. The improved FOA-GRNN (IFOA-GRNN) model was compared with the radial basis function (RBF) and GRNN models. The results showed that the IFOA-GRNN model had a better convergence accuracy, the highest average recognition rate (96.4 %), the shortest average calculation time (275 s), and a good recognition rate under noise interference. The experimental results show that the IFOA-GRNN model has a good performance in radar target recognition and can be further promoted and applied in practice.