Home – Home – Jornals – Avtometriya 2019 number 1

The paper presents a mathematical apparatus based on the requirement of preserving tautochronism in each of the diffraction orders of a harmonic kinoform lens. The apparatus was used as the basis of a method for calculating the lens microstructure.яThe method limits the relative longitudinal chromatism of the lens to a given level and provides the initial parameters necessary for the radial calculation and optimization of the optical system with a harmonic kinoform lens using well-known commercial optical design computer programs

The present study is aimed at solving the problem of in situ thermometry of low-temperature processes of molecular beam epitaxy of indium antimonide. A spectral ellipsometric method for measuring the temperature of InSb epitaxial layers is proposed. The method is based on the temperature dependence of the energy positions of the critical points. The spectra of ellipsometric parameters of the material in the temperature range from 25 to 270^o are measured. The analysis of these spectra shows that the most temperature-sensitive parameters are the spectral positions of the peaks of the ellipsometric parameter Ψ, which are manifested near the critical points E1 and E1 + Δ1. It is found that the dependences of the peak positions on temperature in the above-mentioned temperature range are linear functions with the slope factors of 0.21 and 0.10 nm/^o, respectively. These factors determine the sensitivity of the method and ensure the temperature measurement accuracy within 2-3^o

Diffusion burning of a hydrogen jet is studied by methods of the Hilbert optics. A diagnostic system based on the batch-produced IAB-463M device is implemented, which includes a specially developed Hilbert filtration module coupled with a light source. The influence of local turbulent perturbations (puff or slug) arising in the tube forming the jet on the dynamic structure and flame evolution is revealed. This phenomenon can be used to control the space-time structure of the flame

A procedure of layer-by-layer investigations of characteristics of thick amplitude-phase gratings by the method of laser heterodyne tomography is presented. The parameters of a thick grating nonlinearly written on an additively colored crystal of calcium fluoride (CaF2:Na) are estimated. The main theoretical postulates of laser heterodyne tomography are experimentally validated

The effect of the photoresponse nonlinearity of a holographic material on the achievable diffraction efficiency of holograms has been studied.яIt has been shown that the interaction between the hologram form factor and the photoresponse nonlinearity leads to an increase in diffraction efficiency in comparison with a linear photoresponse. Numerical calculations for the photoresponse nonlinearity corresponding to Reoxan phase holographic material are presented

The direct problem of light scattering for a fiber optic Bragg grating is considered.яThe formulation and solution of the problem based on the transfer matrix method are discussed.яA variant of the method is proposed which reduces to a a universal recurrent algorithm similar to the sweep algorithm and convenient for computing.яThe elements of transfer matrices were calculated with the third local order of accuracy on an uneven computational grid along the coordinate in the approximation of coupled modes using the finite volume method.яThe recurrent algorithm was used in numerical calculations for the direct scattering problem for a Bragg grating with apodization and nonlinear chirp.яNumerical simulations confirmed the significant increase in the accuracy of calculations for solving the scattering problem on the nonuniform grid

The mode composition of a four-layer optical waveguide consisting of an ion exchange channel waveguide in glass coated with a highly refractive nanoscale dielectric film has been studied.яIt has been found that varying the geometric dimensions of the film changes the polarization states of the second and third waveguide modes: the TM0 mode is transformed into the TE1 mode, and the TE1 mode becomes the TM0 mode.яBased on this, a new method of constructing a waveguide polarization converter has been proposed and experimentally confirmed

A new terahertz (THz) imager based on THz-to-IR conversion has been proposed and studied.яThe THz-to-IR converter consists of an ultra-thin resonant THz absorber (meta-absorber) whose backside is coated with an emission layer with an emission coefficient close to unity. The absorption of THz radiation causes heating of the converter, which was recorded with an infrared camera from side of the the emission layer.яThe small thickness of the converter (more than 50 times shorter than the working wavelength of THz radiation) determines its low heat capacity, resulting in an increase in the sensitivity and speed of the visualizer.яOptimization of the optics of the THz visualizer, making cuts in the converter structure to Reduce the blooming and increase the response, and the IR image processing method, which increases the signal-to-noise ratio, provide an increased sensitivity of the THz imager at the level of sensitivity of thermal detectors in the 8-12 $\mu$m IR range

Capabilities of some algorithms of interpolation of quadrature signals currently used for creating parallel-type interface blocks for high-resolution transducers of linear and angular displacements are analyzed

The problem of detection and estimation of spatial coordinates of moving objects by a passive scanning system of vision is solved. Algebraic and algorithmic approaches to determining the spatial coordinates and parameters of object motion are proposed. These approaches differ by taking into account the object velocities in searching for conjugate vectors of directions to the objects. The algorithms developed on the basis of these approaches show that the approach with allowance for motion parameters offers significant advantages of higher accuracy of coordinate estimation and higher probability of detecting all objects

The processing of information signal parameters under conditions of inertialess nonlinear transformation of an input mixture of signals and narrow-band non-Gaussian interference Considered.яThe nonlinear processing of signal parameters is analyzed in the ranges of small and arbitrary detuning between the measured signal parameters and their estimates, as well as at a random signal-to-noise ratio at the gauge input.яTwo variants of optimization of a multichannel discriminator by the criterion of the minimum of the generalized rms error and their corresponding structural schemes were obtained.яThe vector of optimal amplitude characteristics of the nonlinear transformation unit.яIt is shown that the discrimination and fluctuation characteristics of the discriminator are given by the average error signal and its dispersion

Mathematical bases of an integral operator for differentiating 2D images in order to increase their contrast are presented. Images are formed by an optic-electronic device under different background conditions. It is proven that the operator suppresses high-frequency components of images, generated by an applicative background and additive noise of the device. The universal property of the operator is determined, from which the known key differentiation operators are derived: gradient, Roberts, and Laplace operators. The results of contrasting real images by the proposed operator are presented

A specifically planned experiment based on obtaining a required family of estimates of supporting integral curves (approximately described in a given finite system of base functions) is used to solve a problem of active identification of a dynamic object, which corresponds to an a priori unknown differential equation. In view of the fact that experimental data may contain fluctuation and singular interference, a method is developed for optimal unbiased estimation of linear numerical characteristics of the object behavior and approximate analytical solution (differential equation), which is valid for a given set of permitted time values and initial condition. The basic characteristics of the method are substantiated, and the results of the computational experiment are presented

This paper systematizes and generalizes data on the specific features, operation modes, and technical characteristics of world-class ground-based solar telescopes in order to obtain information required to develop and design an automated control systems for the large solar telescope included in the National Heliogeophysical Complex of the Russian Academy of Sciences