Optoelectronics, Instrumentation and Data Processing (v.52, #6)

Analysis of random point images with the use of symbolic computation codes and generalized Catalan numbers by A. L. Reznik; A. V. Tuzikov; A. A. Solov’ev; A. V. Torgov (529-536).
Original codes and combinatorial-geometrical computational schemes are presented, which are developed and applied for finding exact analytical formulas that describe the probability of errorless readout of random point images recorded by a scanning aperture with a limited number of threshold levels. Combinatorial problems encountered in the course of the study and associated with the new generalization of Catalan numbers are formulated and solved. An attempt is made to find the explicit analytical form of these numbers, which is, on the one hand, a necessary stage of solving the basic research problem and, on the other hand, an independent self-consistent problem.
Keywords: random image; computer analytical calculations; generalized Catalan numbers; random compact groups

Methods are proposed to reconstruct object images and estimate the hardware function in a millimeter-wave radiometric system with a large elevation scanning step. These methods generalize the available approaches to image reconstruction in the spatial and frequency domains with a thinned observation matrix, and provide new approaches to estimating the hardware function. The results of experimental studies are given.
Keywords: image reconstruction; hardware function; thinned matrix; convolution; matrix methods; gradient method; iterative method; Wiener filter

Issues related to measuring the information parameters of signals reflected from an object under correlated additive non-Gaussian noise are considered. It is shown that in the presence of correlated non-Gaussian noise, increasing the correlation coefficient increases the generalized signal/noise ratio, which, in turn, improves the measurement accuracy of signal parameters. The obtained dependences confirm that the measurement error of signal information parameters is affected not only by the generalized signal/noise ratio, but also by accounting for the non-Gaussian nature of the additive noise, which leads to a significant improvement in the measurement accuracy of these parameters.
Keywords: variance of measurement error; correlated additive non-Gaussian noise; signal information parameters

This paper presents a comparative analysis of the errors of two alternative methods of estimating the central frequency of signals of laser Doppler systems, one of which is based on the maximum likelihood criterion and the other on the so-called pulse-pair technique. Using computer simulation, the standard deviations of the Doppler signal frequency from its true values are determined for both methods and plots of the ratios of these deviations as a measure of the accuracy gain of one of them are constructed. The results can be used by developers of appropriate systems to choose an optimal algorithm of signal processing based on a compromise between the accuracy and speed of the systems as well as the labor intensity of calculations.
Keywords: laser Doppler measuring systems; optimal signal processing methods; most likely estimates

Results of developing control algorithms for an active power filter operating as a fast-response current source are presented which provide a significant improvement in the energy consumption performance in the case of a nonlinear load of arbitrary form with a simultaneous possibility of generating reactive power at the fundamental frequency.
Keywords: active filtering algorithm; instantaneous power; compensation current quaternion

Spectral method for processing signals of a high-accuracy laser radar by A. V. Klimov; V. G. Glavnyi; G. V. Bakakin; V. G. Meledin (563-569).
A spectral method is proposed to determine the signal frequency and readings of a laser radar with a frequency modulation of the reference channel based on signal preprocessing with a Gaussian window and calculation of its spectral centroid. Numerical simulation and experiments with a frequency modulation band 5–20 MHz wide have shown that this method provides an order of magnitude better accuracy than the conventional spectral analysis methods.
Keywords: laser radar; frequency modulation; spectral analysis; nonparametric estimation; spectral centroid algorithm; Gaussian window; accuracy improvement

Specific features of half-plane image formation in a spatially noninvariant (aberration-free) coherent optical system of the 2F–2F telecentric type with a limited aperture of the projection objective (in the absence of the spatial frequency filter) are studied. The dependence of the light intensity behavior at a point corresponding to the half-plane edge in the image on the object position is found in an analytical form on the basis of approximating the Fresnel functions by analytical functions. As the half-plane approaches the boundary of the field of vision of the system determined by the objective aperture diameter, the light intensity is demonstrated to deviate significantly from that in the case of the axial position of the half-plane, which may lead to noticeable measurement errors in inspecting the geometric parameters of objects by the projection method in transmitted light.
Keywords: light diffraction; telecentric projection systems; Fourier optics; dimensional inspection

Boson peak in low-frequency Raman spectra of polymethylmethacrylate by M. A. Korshunov; V. F. Shabanov (580-584).
The role of the local field, anharmonicity, and degree of disorder in the formation of the boson peak has been studied. The low-frequency Raman spectrum of a model polymethylmethacrylate crystal with disorder elements was calculated using the method of atom-atom potentials taking into account the effect of local fields on the spectrum. The calculations were carried out for a crystal containing rigid molecules of an isotactic polymethylmethacrylate oligomer and for a structure with flexible molecules.
Keywords: boson peak; Raman spectra; anharmonicity; modeling

Measurement of the characteristics of ultrahigh-frequency optical modulators by a scanning interferometer by S. N. Atutov; S. L. Mikerin; A. E. Simanchuk; V. A. Sorokin; A. I. Plekhanov (585-591).
Results of studying an original method of the modulated optical radiation spectrum analysis and testing a simple detector based on the Fabry–Perot interferometer are reported. The theoretical analysis of detector operation is compared with model experiment results. A possibility of using this analyzer for measuring the characteristics of ultrahigh-frequency modulators of optical radiation operating at modulation frequencies from 10 to 100 GHz and higher is noted.
Keywords: electro-optic modulator; detection of modulated radiation; electro-optic polymers

Optoelectronic scanning system upgrade by energy center localization methods by W. Flores-Fuentes; O. Sergiyenko; J. C. Rodriguez-Quiñonez; M. Rivas-López; D. Hernández-Balbuena; L. C. Básaca-Preciado; L. Lindner; F. F. González-Navarro (592-600).
A problem of upgrading an optoelectronic scanning system with digital post-processing of the signal based on adequate methods of energy center localization is considered. An improved dynamic triangulation analysis technique is proposed by an example of industrial infrastructure damage detection. A modification of our previously published method aimed at searching for the energy center of an optoelectronic signal is described. Application of the artificial intelligence algorithm of compensation for the error of determining the angular coordinate in calculating the spatial coordinate through dynamic triangulation is demonstrated. Five energy center localization methods are developed and tested to select the best method. After implementation of these methods, digital compensation for the measurement error, and statistical data analysis, a non-parametric behavior of the data is identified. The Wilcoxon signed rank test is applied to improve the result further. For optical scanning systems, it is necessary to detect a light emitter mounted on the infrastructure being investigated to calculate its spatial coordinate by the energy center localization method.
Keywords: analysis; energy center; compensation; localization; optical method

A method of measuring the velocity of Hilbert-visualized phase structures by means of emulation of two-dimensional spatial filtering of their images formed on the matrix of a digital camcoder is discussed. As an example, visualized fields of the phase optical density in convective flows induced in a high-viscosity fluid are considered. Investigations of this kind of flows are useful for simulating the Earth’s mantle behavior at large depths.
Keywords: velocity field measurement; emulation of two-dimensional spatial filtering of images; Hilbert-visualized phase structures; thermogravitational convection

This study describes the laser generation of a 6Zh rhodamine in artificial opals representing single-crystal and heterostructure films. The spectral and angular properties of emission and the threshold characteristics of generation are investigated. In the case where the 6Zh rhodamine was in a bulk opal, the so-called random laser generation was observed. In contrast to this, the laser generation caused by a distributed feedback inside the structure of the photonic bandgap was observed in photonic-crystal opal films.
Keywords: photonic crystal; laser generation; opal; heterostructure

The properties of polarization holographic gratings formed in liquid crystal polymer composites doped with inorganic nanoparticles (SiO2, ZnO, Al2O3, and Y2O3) are considered. The effect of these additives on the phase transition temperature of liquid crystals of polarization gratings, diffraction efficiency, and driving voltage is demonstrated.
Keywords: liquid crystals; liquid crystal composites; nanoparticles; polarization holography

The development of additive technologies and their application in industry is associated with the possibility of predicting the final properties of a crystallized added material. This paper describes the problem characterized by a dynamic and spatially nonuniform computational complexity, which, in the case of uniform decomposition of a computational domain, leads to an unbalanced load on computational cores. The strategy of partitioning of the computational domain is used, which minimizes the CPU time losses in the serial computations of the additive technological process. The chosen strategy is optimal from the standpoint of a priori unknown dynamic computational load distribution. The scaling of the computational problem on the cluster of the Institute on Laser and Information Technologies (RAS) that uses the InfiniBand interconnect is determined. The use of the parallel code with optimal decomposition made it possible to significantly reduce the computational time (down to several hours), which is important in the context of development of the software package for support of engineering activity in the field of additive technology.
Keywords: domain decomposition; numerical simulation; additive technologies; OpenFOAM

Development of analog-digital readout integrated circuits for infrared focal plane arrays by M. A. Dem’yanenko; A. I. Kozlov; I. V. Marchishin; V. N. Ovsyuk (630-636).
This paper describes the design of readout integrated circuits (ROICs) for hybrid infrared focal plane arrays (IR FPAs). This work contains the estimation of the noise equivalent temperature difference (NETD) of IR FPAs based on frame and row integration of pixel signals in the spectral ranges of 8 to 14 and 3 to 5 μm. This paper also describes the development of ROICs for IR FPAs created with the use of mercury—cadmium—telluride (MCT) photodiodes and quantum well infrared photodetectors (QWIPs). The designed ROICs ensure the use of matrix and linear photodetector chips, including those with increased dark currents, in order to produce IR FPAs with temperature resolution corresponding to the world level of array analogs.
Keywords: readout integrated circuit; infrared focal plane array; cadmium — mercury — telluride photodiode; quantum well infrared photodetector