Optoelectronics, Instrumentation and Data Processing (v.49, #2)

Various approaches to solving the problem of filtration of a continuous periodic signal distorted by stationary additive non-correlated noise are considered. Particular attention is paid to the case where the known signal period is non-divisible by the signal sampling period.
Keywords: filtration; non-correlated noise; non-divisibility of the signal period by the sampling interval

Two methods of statistical estimation of the optimal regularization parameter of a nonlinear algorithm for signal recovery are proposed, one of which is based on the optimality criterion and the other one on the residual principle. These methods have simple algorithmic implementation and do not need a priori information about the quantitative characteristics of the sought solution. The results of numerical experiments show the effectiveness of the method based on the optimality criterion.
Keywords: signal and image recovery; nonlinear regularization algorithms; threshold wavelet filtering; estimation of optimal regularization parameter

The effect of reduction of the signal sampling frequency by the signal mean value in the case of superposition of a harmonic noise component onto the original steady stochastic signal is studied. Conditions under which reduction of the observation frequency of this process significantly changes the observed mean values are found. In this regard, a number of statements are formulated and proved. The consequences of a reduction of the observation frequency of the dynamometer signal for the experiment performed in an ice basin with a tanker hull model are considered..
Keywords: signal analysis; signal sampling; harmonic signal; ice loads

An approach to 3D image processing based on the modified generalized Hough transform is proposed. The possibility of processing images with unknown rotation and scaling parameters and images represented by individual fragments of the original image is shown. The efficiency of the proposed algorithms for solving problems of 3D image recognition is studied.
Keywords: 3D image recognition; generalized 3D Hough transform; invariance to rotation and scaling

This paper presents an algorithm for determining the coordinates of small objects appearing in a sequence of scene images based on sum and difference processing of the detailing wavelet coefficients of the current and reference images, followed by a morphological analysis of the generated pseudo-image. The effectiveness of the algorithm is compared with the difference algorithm for analyzing changes in the observation scene. It is shown that the proposed algorithm is more resistant to the effects of relative shifts of the current and reference images.
Keywords: wavelet transform; search for small objects; morphological image analysis

Tracking of several objects in a seismic detector by S. A. Alyamkin; E. S. Nezhevenko (148-154).
Methods of processing of seismic signals from antennas of two seismic receivers for localization of several objects are considered. The possibility of localization is provided by means of multiplicative or broadband processing; in this case, a multielement antenna having a narrow direction diagram is synthesized from two detectors. The efficiency of the approaches based on localization of two sources of the signal is demonstrated by an example of modeling and real seismic data.
Keywords: seismic detector; localization; direction characteristic; multiplicative antenna

Various filtration methods are compared by an example of processing of model and experimental vector fields. A criterion for estimating the filtration efficiency is proposed. It is demonstrated that combined vector filters ensure more efficient filtration than other popular methods.
Keywords: filtration; noise; vector fields; shear strain intensity

Analysis of multiple cracking of nanocoating as a cyclic random process by I. V. Lytvynenko; S. A. Lupenko; P. O. Marushchak (164-170).
A mathematical model of multiple cracking of a zirconium nanocoating is proposed that makes it possible to obtain informative characteristics for quantitative analysis of the cracked surface taking into account the stochastic and cyclic nature of the process is proposed.
Keywords: model; cyclic random process; multiple cracking; nanocoating

Classification measurements: Methods and implementation by V. V. Gubarev; A. A. Gorshenkov; Yu. N. Klikushin; V. Yu. Kobenko (171-177).
This paper considers the conceptual apparatus, basic ideas, structure, and some features of the establishment and development of a new area of research that emerged at the intersection of measurement theory and applied statistics. Examples and methods of solution of problems of classification measurements of random signal distribution shapes and the state of rechargeable batteries based on the use of categorical measurement scales are described.
Keywords: algorithm; diagnosis; categorical measurement scale; classification; model; result reliability

Solution of the problem of phase ambiguity by integer interferometry by I. I. Guzhov; S. P. Il’inykh; R. A. Kuznetsov; A. R. Vagizov (178-183).
An automatic method is proposed to resolve phase ambiguity in interpreting fringe patterns by a series of two phase distributions with different periods. The method does not require identification of local phase transitions in adjacent image regions and can determine the total phase at each point separately.
Keywords: optics; interferometry; phase-shifting interferometry; resolution of phase ambiguity

Terahertz microlens array emitter based on the transverse Dember cross effect by V. D. Antsygin; A. S. Konchenko; V. P. Korol’kov; A. A. Mamrashev; N. A. Nikolaev; O. I. Potaturkin (184-188).
A new method for generating terahertz radiation by exposure to femtosecond laser pulses on the semiconductor surface is proposed. The essence of this method is that the exciting radiation intensity is subjected to spatial modulation by using a microlens array and by shading a part of the semiconductor surface by metal stripes. This gives rise to a concentration gradient of photo carriers along the surface at the sharp boundary of the metallic coating in the semiconductor (transverse Dember photoelectric effect), and its relaxation for times of ∼1 ps results in the emission of electromagnetic pulses of the terahertz range. A terahertz emitter model based on the proposed method was developed and designed, its efficiency was demonstrated, and methods for increasing its efficiency were considered.
Keywords: terahertz radiation; Dember effect; Talbot effect; femtosecond laser; array illuminator

Silicon diffractive optical elements for high-power monochromatic terahertz radiation by A. N. Agafonov; B. O. Volodkin; A. K. Kaveev; B. A. Knyazev; G. I. Kropotov; V. S. Pavel’ev; V. A. Soifer; K. N. Tukmakov; E. V. Tsygankova; Yu. Yu. Choporova (189-195).
This paper presents a fabrication technique and results of studies of silicon binary diffractive optical elements (DOEs): a diffractive lens and a 1 : 2 diffractive beam splitter with an aperture diameter of 30 mm for the terahertz spectral range. The elements were fabricated in two versions: with and without an antireflection coating of parylene C. The DOE characteristics were investigated in the beam of the Novosibirsk free electron laser at a wavelength of 141 μm. The results are given of a study of the radiation resistance of the coating, which remained intact upon exposure to an average radiation power density of 4 kW/cm2; the peak power in a 100 ps pulse was almost 8 MW/cm2. Experimental estimates of the diffraction efficiency of the elements coated with the antireflection coating are in good agreement with theoretical estimates.
Keywords: DOE; terahertz radiation

Measurement of bubble and droplet diameters by the Doppler anemometry by A. P. Belousov; P. Ya. Belousov; L. A. Borynyak (196-203).
Interaction of a probing laser beam with a liquid droplet is analyzed theoretically. It is shown that the amplitude of the Doppler signal obtained from a moving droplet depends on its position with respect to the beam waist. The possibility of determining the radii of droplets and bubbles moving in the flow from the spatial positions of the extreme points of the Doppler signal amplitude is justified theoretically and experimentally. The radius of glass spheres is measured (1.75 and 5 mm). The relative error of measurements is 1.1 and 8%. The radius of bubbles upfloating in a viscous liquid is measured. It is shown that the proposed method based on the Doppler anemometry offers prospects in studying two-phase flows.
Keywords: gas-liquid flows; Doppler diagnostics; droplet size; sampling area

New microelectromechanical cavities for gigahertz frequencies by E. G. Kostsov; S. I. Fadeev (204-210).
A possibility of creating micrometer-sized microelectromechanical cavities operating at gigahertz frequencies is considered. A thin film of a dielectric (ferroelectric) with a high dielectric permeability and electric strength is included into the cavity structure. Specific features of device operation and its structure are described by a mathematical model that allows one to find exact relations between the parameters characterizing natural oscillations of the moving element and the triggering voltage.
Keywords: microwave MEMS; microcavity; frequency generator; HF filter; natural oscillations

Trends of increasing the informative content of the thermal imaging channel of optoelectronic observation devices are discussed, and a method of using the properties of the intrinsic polarized thermal radiation from objects to determine their three-dimensional shape is considered. The paper presents a model system for obtaining polarization thermal images and the mathematical model and results of experiments on the production and processing of polarization thermograms of objects and determination of their three-dimensional shape.
Keywords: polarization; intrinsic thermal radiation; polarizer; three-dimensional shape; polarization thermogram