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.