Computer Optics

155-159

Authors: I.N. Chuprina, A.A. Kalachev

The work is devoted to the problem of developing integrated single-photon sources based on spontaneous four-wave mixing in ring microresonators. Considering the silicon nitride microresonator as an example, we calculate the group velocity dispersion in a wide wavelength range for the case when the ring resonator is composed of straight and curved sections, and show that for different pump wavelengths it is possible to find an optimal ratio of the height and width of the waveguide, thereby achieving zero group velocity dispersion at a minimum height. Such waveguides, which provide zero dispersion and have a minimum height, are optimal for creating ring microresonators that generate single-photon states via non-degenerate spontaneous four-wave mixing.

169-174

Authors: A.S. Machikhin, L.I. Burmak , V.E. Pozhar

A scheme of full-field optical coherence microscopy based on a Michelson interferometer with wideband light source and acousto-optic spectral filtration in the output channel is studied. Mathematical formulas for calculating the interference pattern formed by image-carrying light beams diffracted by an acoustic wave in a uniaxial crystal are derived for this scheme. Results of numerical modeling and its comparison with experimental data are given.

183-191

Authors: I.S. Panyaev , D.G. Sannikov

Spectral properties of surface TM-waves (polaritons) are considered in the guiding structure based on a narrow-band semiconductor (n-InSb) and a nanocomposite medium (layered metamaterial) in the mid-infrared region (5÷20 µm). The nanocomposite medium has a weak gyrotropy and contains layers of bismuth-doped iron garnet (BLIG, Lu3-xBixFe5-yGayO12) and gallium-gadolinium garnet (GGG, Gd3Ga5O12) layers magnetized to saturation. Solutions of the dispersion equations are investigated for the cases of linear and nonlinear response of the semiconductor. For an analytical description of the nonlinear response of the structure we use the «uniaxial» (longitudinal) and «biaxial» approximations. Dispersion spectra for the propagation constant, as well as field and energy characteristics of the surface polaritons are obtained and analyzed. Regions of the existence of soliton-like wave-fields of the surface polaritons are found for each of the description methods used. It is shown that the «uniaxial» model may be unsuitable for the calculation of the electromagnetic fields and energy flows in the structures based on cubic nonlinear media.

202-207

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

In the article we show in the geometric approximation the possibility of slowing down the light propagating along the axis of an optical waveguide structure by using metamaterials as optical structure elements. We study features of light propagation using a plane model of a fiber optic line whose cladding material has a negative refractive index. It is shown that by introducing a metamaterial, the propagation of light waves in the structure can be changed so that the light is decelerated along the structure axis to the extent that it stops, before starting to propagate in the opposite direction. We derive relationships for calculating the delay time as a function of geometrical and optical parameters of the structure, relationships for calculating critical parameters, and сonditions for stopping the light.

218-226

Authors: G.I. Greisukh , E.G. Ezhov , S.V. Kazin , S.A. Stepanov

Conditions that guarantee the absence of a visually observed halo in the image formed by the camera of a mobile communication device containing a diffractive lens with a single-layer sawtooth phase microrelief are corrected. The feasibility and effectiveness of using the diffractive lens with a single-layer microstructure, which does not lead to the emergence of a visually observable halo, are demonstrated by the example of a plastic objective lens for the smartphone.

237-244

Authors: Y.B. Blokhinov, A.V. Bondarenko, V.A. Gorbachev, S.Y. Zheltov, Y.O. Rakutin

A method for counterfeit bill detection based on a digital image for mass-production smartphones is developed. The method under consideration does not require new protective elements to be designed and introduced into the print and is based on the use of digital image analysis and recognition methods, allowing one to carry out an automatic search and verification of known protective elements of the print. The peculiarity of the proposed approach is associated with constructing a feature vector for each type of samples and their subsequent classification using machine learning based on a training sample. The method is realized as a program application for smartphones, performing the automatic detection of an object in the frame, shooting the cameracaptured object, rejection of unsuitable images, determination of a face-value and type of the banknote, and finally, verification of the authenticity.

254-265

Authors: Y.V. Vizilter, V.S. Gorbatsevich, A.V. Vorotnikov, N.A. Kostromov

This paper presents a new approach to constructing a biometric template using a Convolutional Neural Network (CNN) with Hashing Forest. The approach consists of several steps: training a convolutional neural network, transforming it to a multiple convolution architecture, and finally learning the output hashing transform via a new Boosted Hashing Forest technique. This technique generalizes the Boosted SSC (Similarity Sensitive Coding) approach for hashing learning with joint optimization of face verification and identification. The proposed network via hashing forest is trained on the CASIA-WebFace dataset and evaluated on the LFW dataset. The result of coding the output of a single CNN is 97% on LFW. For Hamming embedding, the proposed approach enables a 200 bit (25 byte) code to be constructed with a 96.3% verification accuracy and a 2000-bit code with a 98.14% verification accuracy on LFW. The convolutional network with hashing forest with 2000×7-bit hashing trees achieves 93% rank-1 on LFW relative to the basic convolutional network's 89.9% rank-1. The proposed approach generates templates at the rate of 40+ fps with a GPU Core i7 and 120+ fps with a GPU GeForce GTX 650.

276-283

Authors: V.L. Karyakin

This research studies in which way the interference that occurs in Single-Frequency Networks for Digital Television broadcasting affects the reception quality in the overlapping service zones of transmitters. The article contains qualitative and quantitative evaluation of the effectiveness of the interference distortion compensation in the receiver’s demodulator. The results were obtained using CADs VSS Applied Wave Research and ADS Agilent Technologies and allow us to evaluate a limiting value of the signal-to-echo-signal ratio for a given signal-tonoise ratio that provides the network operability. The DVB network operability in the presence of transmitter clocking depends on the stability margin, which is defined by the permissible value of a bit error rate (BER) within a threshold. From the obtained results it follows that the interference-impact threshold corresponds to the BER equal to 2×10-4. For below-threshold BER values, the reception becomes almost error-free due to the use of a ReedSolomon decoder. Codec replacement in the second-generation DVB networks resulted in a significantly decreased BER threshold value to 10-2 – 10-3, which allowed the data transfer rate to be increased while keeping the stability margin in terms of the bit error rate. The developed method for studying the performance of digital broadcasting networks and systems allows causes behind the increase of BER to be identified in practice based on spectra and signal constellations diagrams, also enabling the comparison of various algorithms for the assessment of data channel performance and digital television signal processing in terms of the effective suppression of interference distortions.

291-294

Authors: A.V. Demin, P.V. Rostokin

This paper presents an alignment algorithm for composite telescope mirrors. Introducing the concept of a differential surface and a comparator principle we deduce relationships for evaluating the alignment accuracy for composite mirrors. This algorithm assumes the implementation of the geometrical and optical positioning of mirror segments.