Home – Home – Jornals – Avtometriya 2018 number 1

The relationship of the diffraction efficiencies of volume reflection holograms obtained with the use of double-beam and single-beam recording schemes in absorbing light-sensitive materials is studied theoretically and experimentally. This relationship is demonstrated by an example of a particular photopolymer material.

An important aspect of the development of specialized test rigs for monitoring and estimating information system parameters is the use of devices for test field generation. Simulation rigs based on micromirror modulators capable of real-time generation of dynamic (tunable) images are considered in the present study. For such modulators to be used in the long-wave infrared range of the spectrum, they are upgraded by means of replacement of usual protective glasses by materials that are transparent in the infrared range up to the wavelength of 14 m. Structural features of the test rigs are considered on the basis of the description of micromirror modulators in the form of echelettes (diffraction gratings with a saw-tooth shape of the grooves. Experimental results are presented. The ability of upgraded modulators to operate within infrared simulation rigs is demonstrated. Such devices offer certain prospects for the development of advanced systems for monitoring and dynamic testing of infrared photodetectors.

This paper describes the analysis of the potential accuracy of estimating the signal modulation index of a homodyne laser Doppler vibrometer with frequency modulation and known and unknown non-information parameters of the signal. The Rao - Cramer inequality is used to obtain expressions for calculating the lower boundary of variance of the modulation index estimate and study its relationship with a signal/noise mixture. Recommendations on the choice of conditions for measuring the amplitude of vibro-displacement by the homodyne Doppler laser vibrometer are given.

Results of an experimental study of the density distribution in a small-size (1-2 mm in diameter) supersonic gas jet in vacuum are reported. The measurements are performed by the developed Shack-Hartmann wavefront sensor, which consists of a microlens array with 100 × 100 elements and a video camera with a resolution of 2048 × 2048 pixels. The reliability of measurements in terms of the space and time resolution, as well as in terms of the minimum levels of phase changes induced by the tested object, is analyzed.

The possibility of using synthesized Fresnel holograms to determine phase distortions of the wavefront has been studied. The results of computer simulation of the propagation of an elementary signal based on the Fresnel integral transformation are presented. The principle of operation of a hologram for a wavefront sensor is discussed.

Molecules with strong two-photon absorption have applications in photodynamic therapy and photonic devices. The effect of polarity of the medium and microemulsion on nonlinear optical properties of saffron is studied by the Z-scan technique with a CW laser at the 532 nm wavelength. The values of the nonlinear refractive index and two-photon absorption of saffron are found to increase with a decrease in the medium polarity and with an increase in the droplet size in the microemulsion.

Experimental investigations of nonlinear optical and electro-optical properties of original synthesized chromophore-containing polyimides with a covalently attached dye DR-13 are reported. The data measured by the method of second harmonic generation are compared with the results of direct measurements of the electro-optical response by the Teng-Man method. High temperature stability of the examined polyimides is observed. Methods of creating a planar phase electro-optical modulator with the use of synthesized chromophore-containing polyimides are considered and applied in experiments. The optical and electro-optical characteristics of the modulator are presented.

A prototype of a key element of adaptive-optical systems - a controlled flat mirror used to correct light beam tilts - was designed. An algorithm for correcting atmospheric distortions of low-intensity light waves and real-time software were developed. In laboratory experiments, a bandwidth of the closed system of 100 Hz was achieved. The efficiency of the developed software was confirmed by daytime observations of stars.

Features of designing objectives telecentric in object space are discussed. The optical circuits of three telecentric objectives developed for dimensional control systems using the shadow projection method are presented. A quality control method for the manufacture of such objectives which have small distortion (less than 0.02 %) and small non-telecentricity (less than 0.01º) is described. Comparison of experimentally obtained optical characteristics of two objectives manufactured by us and one objective manufactured by the Thorlabs company (U.S.) is carried out.

This paper presents an algorithm for processing the transmission spectra of optical microcavities with whispering gallery modes for use as a nanoparticle detector. The algorithm is based on the broadening of the microresonator resonance curve by precipitation of nanoparticles on the microresonator surface. Experimental results on the detection of particles are compared with Langmuir adsorption theory. The contribution of the instability of the excitation radiation source caused by temperature drift of the resonant frequency to the measurement error is estimated.

Metrological analysis of triangulation laser sensors for detecting distances to specular surfaces was performed. Theoretical and experimental studies have established that the measuring range distance depends on the angle of incidence of the laser beam, and the main factor that affects the measurement accuracy is the rotation of the sensor in the plane of incidence. A design of a non-contact detector of the distance to a liquid surface is proposed which provides signaling upon reaching a predetermined value. An overview of triangulation measurement systems is given.

The efficiency of the methods of controlled spectral and spectral-spatial classification of vegetation types on the basis of hyperspectral pictures with different methods of training set formation is evaluated. The dependence of the classification accuracy on the number of spectral features is considered. It is shown that simultaneous allowance for spatial and spectral features ensures high-quality classification of similarly looking types of vegetation by merely using training sets with the maximum degree of the pixel distribution over the image.

This paper describes the urgent task of providing scalability of calculations in the solution of multiextremal problems arising in different branches of scientific studies, including image processing. There is an approach proposed for the development of the Gradient scalable application for the solution of the problem of global optimization of multiextremal functions with account for a multistart method in the Orlando instrumental complex. An additional step of calculations is implemented in the solution of the problem, which makes it possible to decompose the problem with account for the performance of computational resources and thereby minimize the time it takes to solve it as opposed to a classical multistart method. Special agents of the metamonitoring system for measuring the performance of resource with regard to the problem solved.

This paper describes the goodness-of-fit test based on binomial probability distribution, which reduces to a sequence of two-sided hypothesis test for the value of the probability distribution function with different values of its argument. It is shown that each element of this sequence is unbiased locally by the most powerful test. This paper proposes an algorithm for calculating the significance level, free of probability distributions. The quality of this criterion is tested by numerical modeling.

The Smith scheme of inclusion of a sequential compensator into a direct branch of a projected system for the analysis of the quality of processes in steady state is under consideration. This scheme is an effective way of solving the problem of providing the system with a required reserve of stability by removing the link of pure delay beyond a closed loop. The effect of delay is only manifested in the fact that the duration of the transient process increases by an amount of delay without changing the overshoot. It is determined that the velocity quality factor of the system with the Smith scheme of inclusion of a sequential compensator cannot theoretically be larger than the reciprocal of the delay. This paper demonstrates the possibility of reducing this negative property of the Smith scheme of inclusion of a sequential compensator by “pseudocompensation” of lag with differentiating links.

The results of a simplified analysis of a differential measuring circuit with pulsed supply of the single-coil eddy current sensors connected to the circuit, with approximate differentiation of the currents, and with an output ADC. The circuit is designed as part of automation systems for tests of gas turbine engines. Methods for eliminating the effect of temperature on the sensors using the hardware and software of the measurement system are considered. A The families of transformation functions (dependences of the code on the desired radial and axial displacements) for the normal and nominal temperatures were determined using a model of the measuring circuit, and the differences of these families were used to determine the family of functions of temperature influence on code changes, which characterize possible errors. Quantitative estimates of the maximum values of the influence functions are given which confirm the efficiency of the proposed methods.