Optoelectronics, Instrumentation and Data Processing (v.49, #1)

A model of the direction-finding characteristic of a moving point object for a persistent photodetector is proposed. The model ensures the calculation of the direction-finding characteristic as a function of photodetector parameters and object velocity, which form the basis for calculating the probability of detection of moving point objects. Results of numerical experiments are reported.
Keywords: photodetector; direction-finding characteristic; point object

Codes and algorithms are developed for detecting small-size dynamic thermal objects on the basis of searching for space-time anomalies in the observation field formed by a sequence of infrared images. Results of studying the method effectiveness, based on data obtained under conditions of a real background-target environment, are presented.
Keywords: search for dynamic objects; small-size objects; processing of IR video sequences; space-time anomalies

This paper describes a new method for choosing a distribution law from a given set of experimental data that provides the best fit to a measured random variable. The method is based on a comparison of empirical distributions constructed for the original sample with the set of given laws using a continuous mapping of the distribution function onto the interval [0, 1]. As a result, the distribution for which the corresponding value of the functional is maximal is taken as the most probable distribution law for the original sample. Examples of implementing the method using statistical Monte Carlo simulation are given.
Keywords: random variable; distribution law; probability density; random sampling; Monte Carlo statistical simulation; goodness-of-fit test

The problem of computing spline approximation functions taking into account the possibility of optimizing the location of spline nodes is considered. Algorithms are developed to compute spline approximation functions with free conditions at the ends of observation intervals, with controlling of splines by the zero and first derivatives at the ends of observation intervals, and with the provision of optimal locations of spline nodes. The results of mathematical modeling of the algorithms for computing spline approximation functions are presented.
Keywords: digital filtering; approximation; optimization; spline functions; spline nodes

Application of the fractal dimension for estimating surface images obtained by various detectors by S. V. Panin; Yu. A. Altukhov; P. S. Lyubutin; A. V. Byakov; S. A. Khizhnyak (34-40).
The influence of various methods of obtaining surface images on the calculated value of their fractal dimension as a quantitative characteristic of the surface state is studied. It is demonstrated that images obtained both by a scanning electron microscope and by a photocamera are characterized by a noticeable noise level, which alters the behavior of the fractal dimension. Various methods of correction of the observed effect are discussed.
Keywords: fractal dimension; image processing; filtration; optical image; noise

The exchange rate formation process is represented as the sum of a low-frequency deterministic trend and a high-frequency stationary random component for which the covariance function, the spectral density, and the increment correlation function are obtained. Theoretical results are in good agreement with the results of processing of observed data. The model explains the occurrence of Elliott waves on exchange rate paths and generates a parametric family of random processes with spectral characteristics ranging from white noise to a first-order autoregression process.
Keywords: random process; exchange rate; covariance function; spectral density; autoregression processes; Elliott waves

A method for determining the optimal internal parameters of technical systems, based on the analytical description of the operational capability range, which is defined as a set of linear constraints, is considered. An expression for the objective function, which allows one to use any known search method for optimizing the system by the criterion of the operational capability reserve, is derived.
Keywords: parametric synthesis; operational capability range; operational capability reserve; R-functions

By solving coupled-mode equations in laser Doppler tomography, expressions for output signals are found, which describe light diffraction on a volume grating with a mutual (in the general case) shift of the amplitude and phase components. Signal parameters that are least prone to the influence of uncontrolled characteristics of the optical system and studied medium are found. The phase shift between the signals of a two-channel heterodyne detector of scattered light is obtained as a function of the character of the amplitude-phase components of the test grating.
Keywords: acousto-optical scanning; amplitude-phase grating; Doppler tomography; collinear heterodyning; coupled-mode approach; testing of light-sensitive materials

An experimental model of a test rig for formation of images in a computer and insertion of these images into the optical-electron path of an infrared imaging system is considered. Experiments on synthesizing images in the range of 3–5 µm and dynamic scenes are performed. Experimental estimates of the model test rig are given.
Keywords: DLP technologies; micromirror systems; infrared systems; spectral range; IR image

Diffractive attenuators of laser radiation: Fabrication and optical characteristics by A. G. Poleshchuk; A. R. Sametov; V. V. Dontsova; R. V. Shimanskii (72-80).
This paper reports on theoretical and experimental studies of a new class of zero-order diffractive elements — diffractive light attenuators with variable transmission. Results of tests of circular diffractive attenuators for wavelengths of 532 and 1064 nm with amplitude and phase transmission functions are presented. Methods of fabrication of the attenuators are discussed, and the characteristics of prototype modles are considered. It is shown that phase attenuators in the form of embossed circular diffractive gratings with a period of 2 to 6 µm and a variable duty cycle are not selective to polarization and allow controlling the radiation power of pulsed (including femtosecond) and continuous lasers over a wide range (> 100 times).
Keywords: diffraction; phase attenuators; circular diffraction gratings; variable transmission; powerful lasers

Microbeam X-ray lithography apparatus for direct production of deep LIGA structures by B. G. Gol’denberg; E. F. Reznikova; A. G. Lemzyakov; V. F. Pindyurin (81-86).
A microbeam X-ray lithography apparatus, a new device for the direct production of microstructures in thick layers of X-ray resists, in particular, for the fabrication of X-ray lithography masks, was developed on the basis at the LIGA station of the VEPP-3 storage ring of the Siberian Center of Synchrotron and Terahertz Radiation. A microstructure pattern with given arbitrary topology was produced directly in a SU-8 negative resist layer up to 1 mm thick on a substrate moved in a vector mode using a collimated beam of synchrotron radiation with a special software. The design of the device and its technological capabilities and limitations are described. Examples of the fabricated microstructures with a high aspect ratio and X-ray lithography masks are presented.
Keywords: synchrotron radiation; X-ray lithography; LIGA technology

It is predicted theoretically that the combination of elliptically polarized radiation and an antirelaxation coating of the walls of a vacuum cell containing alkali metal vapor provides an asymmetric shape of the magneto-optical resonance. The cause of the asymmetry is the optical pumping of the ground-state hyperfine component which is not destroyed upon collision of the atom with the wall. The effect is most pronounced when the laser frequency is tuned to the resonance with the the FF + 1 transition.
Keywords: magneto-optical resonance; elliptical polarization of radiation; optical Bloch equations

Increasing the mechanical strength of hybrid photodetectors based on mercury-cadmium-telluride heteroepitaxial layers by A. R. Novoselov; I. G. Kosulina; A. G. Klimenko; N. A. Valisheva; V. V. Vasil’ev; S. A. Dvoretskii (94-100).
Results of the research aimed at improving the strength of hybrid photodetectors (PD) based on mercury-cadmium-telluride heteroepitaxial layers are presented. It is shown that annealing of silicon multiplexers at 157 °C in a hydrogen flow in vacuum changes the shape of indium bumps to hemispherical and levels off their mechanical properties over the plate. Controlled recovery of the natural curvature of silicon multiplexer plates and photosensitive element arrays in hybrid photodetectors at 120 °C extends their operation time. A sequence of technological operations on PD hybridization providing an increase in the efforts needed for separating photosensitive elements from silicon multiplexers at least by 75% compared to the PD with fused indium bumps is proposed.
Keywords: photodetector; heteroepitaxial layers of mercury-cadmium-tellurium; indium bumps

Response of nanowire sensors to adsorption of neutral particles by M. A. Il’nitskii; O. V. Naumov; L. N. Safronov; V. P. Popov (101-106).
Results of numerical 2D and 3D-simulations of the performance of nanowire sensors on the basis of silicon-on-insulator structures aimed at determining the optimum conditions for the response to dielectric particles, are given. The effect of screening of nanowires by dielectric particles in solutions with pH = 7 used as a medium for transporting biological objects is considered.
Keywords: nanowires; silicon-on-insulator; sensor; computer simulation