Home – Home – Jornals – Avtometriya 2005 number 1

Synthesis and analysis of the quasi-likelihood and maximum likelihood algorithms for detecting the image of a moving spatially extended object with the unknown intensity against a background with the unknown intensity are carried out for the applicative model of useful image-background interaction.

Solution of the problem of recognizing a group point object is considered for the case when marks of the object recognized are not ordered with respect to marks of the reference object. The solution is carried out based on an amplitude-phase model of a group point object, which represents systems of inherent point domains where noisy object points occur with a high accuracy. Recognition characteristics are constructed.

Imaging systems with a model structure of the type: input image

A new method of identification of dependences on the basis of autoregressive models is proposed. The distinctive feature of the method is verification of the degree of closeness of dimensionless autoregression coefficients to tolerance ranges of the models considered rather than comparison of selected equations. The agreement between trend and autoregressive models is demonstrated. Operation of the method is illustrated by an example of identifying the distance covered by a car after the stop signal as a function of speed.

Results of model tomography reconstruction of a homogeneous region with an inho- mogeneity are presented. Problems concerned with practical application of applying the aperture synthesis in tomography are discussed.

Algorithms for symbol sequence clustering with the use of Levenshtein

A scheme of a diffraction zone-plate interferometer with inverted wavefronts is presented; its modification to record refractive index inhomogeneities with an error below  is proposed. The time variation of transverse distribution of optical inhomogeneity in a potassium-gadolinium tungstate crystal (KGW), caused by a flash of the pump lamp, is recorded. It is revealed that the optical thickness perturbations arising near the pump flashlamp and the thermal variations of the refractive index and the linear dimensions of a sample have opposite signs. This is an indirect evidence of the dominating influence exerted by the photoelastic effects while forming generation in KGW lasers.

Theoretical analysis of microbolometer operation at dc bias is carried out. Four basic signal measurement circuits are considered: at fixed current and voltage, and two modifications of a bridge circuit. Relationships for the noise-equivalent power are obtained taking into account the fluctuations of thermal fluxes, Johnson and  noises of the bolometer, and noises of the readout circuit and the power supply. It is shown that the certain part of noise sources, depending on the measurement circuit, causes fluctuations in the power of the Joule heat emission in the bolometer, and this, in turn, results in increasing temperature fluctuations as the bolometer bias increases. The Joule power fluctuations appear to be comparable (or greater) with the thermal flux fluctuations for metal bolometers.

The initial stages of formation of ZnTe epitaxial films on Si(013) : As are investigated by ellipsometry, reflection high-energy electron diffraction (RHEED), and electron Auger spectroscopy. It is shown that the kinetics of ZnTe film growth is described by the crystal nucleation and growth model. The temperature dependence of the nucleation rate J is adequately approximated by a straight line in the coordinates  ; this evidences the limiting role of critical nucleus dimension formation. The calculated increase of the surface energy while ZnTe nucleating is 40 erg/cm. The estimated value of the pure ZnTe(001) surface energy is 490 erg/cm. The difference between two energy values can be caused by adsorption of the deposited material components, which reduces the excess energy of the surface increasing process.

Certification of diffractive optical elements (DOE) used for aspherical surface testing is considered. The research is concerned with the methods of combining two phase transmission functions in a single DOE in order to form a spherical wavefront in addition to the main aspherical wavefront, whose measurement results can be used to certify the aspherical wavefront. DOE with two diffractive structures combined by dividing the aperture of the element into cells that are alternatively filled with fragments of the structures is analyzed. Three versions of cell shapes are considered, namely, rings, stripes and annular sectors. It is theoretically and experimentally shown that for the configuration with annular sectors the introduced errors are less than in the case of the configuration with rings or stripes. The influence of the cross-talk interference in the case of close spatial frequencies on the error of interference measurement of spherical and aspherical wavefronts is numerically calculated and the ways to reduce it are proposed.

Results obtained by tests and international comparison of different transportable absolute laser ballistic gravimeters designed in Russia (earlier in the USSR) (at the Institute of Automation and Electrometry) and other countries are reviewed. The evolution of increasing measurement accuracy of the absolute gravity acceleration is analyzed.