Computer Optics

599-608

Authors: A.V. Dyshlyuk, O.B. Vitrik, Yu.N. Kulchin

In this paper, we present a numerical study of surface plasmon resonance (SPR) excitation in a bent single-mode optical fiber with metallized cladding. It is shown that with a suitable combination of the bending radius and metal film thickness, surface plasmon waves can be excited in the film as a result of coupling between the fundamental and surface plasmon modes via whispering gallery modes (WGM) supported by the bent fiber cladding. The coupling brings about a dip in the transmission spectrum at the resonant wavelength which is strongly dependent on the ambient refractive index, thus, making it possible to build an SPR- refractometer based on a single-mode fiber without breaking the structural integrity of the fiber or using any additional elements. The refractometric sensitivity of ~12 µm/RIU are demonstrated.

617-625

Authors: A.V. Ustinov

This work deals with a detailed theoretical study of Hermite-Gauss beams with embedded vortical phase passing through a lens. Special attention is given to the location of vortical phase singularities in the focal plane. Sufficient conditions for the intensity null in the focal plane centre are found. The theoretical analysis is confirmed by numerical calculations.

636-644

Authors: N.S. Zakharov , S.V. Kholod

Results of the numerical calculation of the envelope and frequency profile of a pulse propagating in a dispersive medium, exemplified by the propagation of a femtosecond pulse in the plasma, are presented. The explanation for the appearance of modulation in the odd orders of approximation of the theory of dispersion and for the extinction of modulation in the even orders is given. Taking into account the fourth-order term of the approximate dispersion theory is shown to be sufficient in the majority of cases when calculating the ultrashort pulse propagation.

655-660

Authors: A.G. Nalimov

Using the numerical solution of differential Maxwell’s equations, we show that a binary microlens with unit numerical aperture (NA = 1) manufactured in a thin-film amorphous silicon focuses the laser light into a near-surface subwavelength optical focal spot. The microlens contains sectored subwavelength diffraction gratings operating as half-wave plates. The incident light is a linearly polarized plane wave. The micrometalens is numerically shown to operate with near-same efficiency with the number of sectored grating varying from 3 to 16. It is shown that a 16-sector micrometalens generates a focal spot of size at the full-width at half-maximum intensity of FWHMx = 0.435λ and FWHMy = 0.457λ along the Cartesian axes, where λ is the incident wavelength. A 4-sector microlens is numerically shown to focus light into a focal spot of size FWHMx = 0.428λ and FWHMy = 0.46λ.

670-679

Authors: A.A. Dyachenko, V.P. Ryabukho

Regular features in generating coloured interference patterns from single-layer thin objects in polychromatic optical microscopy are considered. Expressions for the intensity distribution of the image interference fields are obtained with due account for the spectral properties of radiation. The proposed algorithm for computer-aided calculation and generation of coloured interference patterns in white light depending on the optical thickness of the layered object is based on a RGB colour model. Numerically simulated interference patterns are presented and changes in their colour and structure under varying parameters of the microscope optical scheme and object optical properties are discussed. We show that it is possible to determine the optical thickness of the object layer through the numerical comparison of interference colours obtained in the natural and numerical experiments.

687-693

Authors: A.G. Glushchenko, E.P. Glushchenko, E.S. Ustinova

The paper considers peculiar features of the Doppler effect that occurs when fundamental and higher-order modes reflect at a movable dielectric layer in multimode waveguides. Relationships for calculating frequencies of different modes of waves that reflect at and pass through the dielectric layer are derived. It is established that with increasing order of the mode, its frequency gets less dependent on the layer motion rate for the reflected waves, at the same time showing a stronger dependence for the transmitted waves. The interaction of waves with the inhomogeneous movable layer leads to the excitation of higher-order modes of the reflected and passed waves, so that each mode corresponds to a different frequency shift (multi-frequency Doppler effect).

701-711

Authors: A.V. Kokoshkin, V.A. Korotkov, K.V. Korotkov, E.P. Novichikhin

This work shows the possibility of estimating errors of super-resolution imaging based on the use of several frames. The possibility of identifying areas with large interpolation errors is shown, based only on the interpolation method and interpolated data used. The possibility of determining the necessary number of frames used for imaging from the interpolation error estimate is demonstrated. In this paper, we present both the results of interpolation of the generated test frames, the method of correlation subpixel detection of frame shifts relative to 1 frame, and the estimates of the resulting interpolation errors. It is shown that before measurements, the number of frames necessary to achieve the required level of interpolation errors can not be predicted. The proposed method allows the error value to be controlled during the measurement. It is shown that the estimation of errors of the super resolution method based on test images is not very promising, since the error value depends both on the image itself and on a set of subpixel offsets of low-resolution frames. We discuss the entire procedure of obtaining the results of the work, starting from the test image generation and ending with the conclusions.

719-725

Authors: E.A. Terekhin

This paper explores the potentialities of discriminant analysis for the identification of abandoned agricultural lands using their reflectance spectrum properties. A method of automated detection of fallow lands is proposed. Using experimental data received from the agricultural lands of the Belgorod Region, we propose equations that allow an agrarian land to be classified as an arable or fallow land in an automated mode. The accuracy of fallow land recognition is 71%. It is found that seasonal normalized difference vegetation index (NDVI) values computed from MODIS data in the period of late September - early October are most informative in terms of abandoned agricultural land identification. It is shown that the use of the minimal NDVI values is much more efficient for the identification of fallow land when compared with the mean NDVI values.

732-742

Authors: M.Yu. Nikitin, V.S. Konushin, A.S. Konushin

This paper addresses a problem of video-based face recognition. We propose a new neural network model that uses an input set of facial images of a person to produce a compact, fixeddimension descriptor. Our model is composed of two modules. The feature embedding module maps each image onto a feature vector, while the face quality assessment module estimates the utility of each facial image. These feature vectors are weighted based on their utility estimations, resulting in the image set feature representation. During visual analysis we found that our model learns to use more information from high-quality face images and less information from blurred or occluded images. The experiments on YouTube Faces and Janus Benchmark A (IJB-A) datasets show that the proposed feature aggregation method based on face quality assessment consistently outperforms naïve aggregation methods.

756-764

Authors: A.S. Yumaganov, V.V. Myasnikov

The work is devoted to solving a problem of searching for similar code sequences in executable binary files. The proposed method involves partitioning the processor instructions into functional groups, forming a given function’s primary description by commands position in its body, followed by generating the function’s intermediate description through its comparison with the functions from a "base" library. With the dimensionality of the resulting vector reduced in this way, the resulting final description is then used to perform the search. Results of the experimental study demonstrate the operability of the proposed method. The efficiency of the proposed method is compared against existing methods of searching for similar code sequences. We also provide recommendations on the choice of parameters of the developed method.

775-785

Authors: D.A. Savelyev

The article gives a summary of major events of the 3rd International Conference and the Youth School on Information Technologies and Nanotechnology (ITNT-2017), which was held in Samara on April 25-27, 2017. Main research topics covered at ITNT-2017 are also briefly reviewed.