Computer Optics

305-310

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

We proved two conservation theorems for the orbital angular momentum (OAM) of a superposition of identical optical vortices with an arbitrary radially symmetric shape, integer topological charge n, and arbitrary off-axis shift. The normalized OAM of such a superposition for any real weights equals the OAM of each individual beam contributing to the superposition. If the beam centers are located on a straight line passing through the origin, then, even if the superposition weights are complex, the normalized OAM of the whole superposition equals that of each contributing beam. These theorems allow of generating vortex laser beams with different (not necessarily radially symmetric) intensity distribution, but with the same OAM. The results of numerical simulation are given for superpositions of Bessel beams, Hankel-Bessel, Bessel-Gaussian and Laguerre-Gaussian beams.

319-323

Authors: Kozlova E.S., Kotlyar V.V.

Numerical simulation of the propagation of picosecond (2.5 ps) and femtosecond (17.08 fs) laser pulses through a dielectric cylinder with a refractive index of 1.59 and a resonance radius of 0,7152λ has shown that as a result, focal spots are generated, which have respective sizes of 0.22λ and 0.235λ at full-width of half-maximum intensity, where λ is the central wavelength of the pulse.

332-338

Authors: Kirilenko M.S., Zubtsov R.O., Khonina S.N.

In this paper we consider the use of a one-dimensional fractional Fourier transform for gradient-index optical waveguides. We calculate eigenfunctions of the transform in view of a limited range in the spatial and spectral domain.

347-356

Authors: Doskolovich L.L., Borisova K.V., Moiseev M.A.

A method for designing a reflective surface to generate a prescribed continuous illuminance distribution is proposed. The optical surface is represented as an envelope of a two-parameter set of ellipsoids of revolution. The efficiency of the proposed method is illustrated with a case of computing and simulation of several reflective surfaces that generate uniform illuminance distributions shaped as an ellipse, a rectangle and a triangle.

363-369

Authors: Khonina S.N., Ustinov A.V., Skidanov R.V., Morozov A.A.

A diffractive aspheric lens with minimized geometric aberrations on the axis (the axilens) is designed. It is shown that the lens possesses substantially higher angular resolution than a parabolic lens. We consider the spectral properties of the axilens. Experiments on imaging by means of an axilens are conducted.

376-384

Authors: Simonenko G.V., Studentsov S.A., Ezhov V.A.

Using computer modeling, the analysis of optical characteristics of a “guest –host” liquid crystal (LC) modulator is conducted. In the article, classical LC modulator designs realized on the basis of a planar cell with various LC twist angles with and without polaroid are considered. Besides, a polaroidfree LC modulator design with homeotropic LC orientation is analyzed. Practical recommendations concerning finding optimum LC modulator designs for various specific purposes are made.

392-396

Authors: Murzin S.P.

The determination of conditions for laser-induced intensification of mass transfer processes in the solid phase of metallic materials was conducted. We studied the process of interdiffusion of Fe and Cu. A laser beam of uniform power density and a pulse frequency of 100, 1,000, and 5,000 Hz was used. The laser radiation was transformed into a uniform light spot with a diffractive optical element, which performed the required focusing. It was determined that for the generalized thermo-dynamic driving force to ensure the mass transfer intensification in non-equilibrium conditions, a necessary condition is the unsteady local deformation caused by laser action.

406-412

Authors: Lisin A.V., Faizullin R.T.

We introduce an approach to image segmentation with a k-means algorithm by reducing the clustering problem to a continuous optimization problem, which is solved by metaheuristics algorithms using a gravitational search algorithm as an example. The approach is substantiated and numerical experiment results are discussed.

420-428

Authors: Mandrikova O.V., Zhizhikina E.A.

We introduce a new method for estimating the geomagnetic field. The method is based on a combination of a wavelet transform with radial basis neural networks. In the method, the recorded geomagnetic field variations are decomposed into different-scale components and the degree of disturbance of each component is estimated, enabling the conclusion about the field state. For the verification of the method, we used geomagnetic data from the "Paratunka" station (Paratunka, Kamchatka region, data registration is carried out by IKIR FEB RAS). Analysis of the spectral-temporal characteristics of geomagnetic field variations during periods of moderate and strong magnetic storms was performed. Weak perturbations were detected in the geomagnetic field before the storms. The obtained results have confirmed the effectiveness of the proposed method.

439-444

Authors: Bagautdinov R.S., Kopenkov V.N., Myshkin V.N., Sergeev V.V., Tribunskiy S.A.

The paper discusses the applicability of satellite images obtained through Earth remote sensing to detecting archaeological objects – burial mounds – that are widely found in the steppe regions of the Samara Region. Requirements for the satellite images that enable the task to be adequately fulfilled are formulated. Methods of computer image processing that provide improved decoding of satellite images (improved object recognition quality) by a human operator are proposed.