Optoelectronics, Instrumentation and Data Processing (v.54, #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.
Keywords: holography; recording media; photopolymer materials; reflection holograms; diffraction efficiency

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 μm. 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.
Keywords: device for generation of infrared images; micromirror modulator; DLP; DMD modulator; echelette; orders of the diffraction grating spectrum

This paper describes the analysis of the potential accuracy of estimation of 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 bound 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.
Keywords: homodyne laser Doppler vibrometer; signal modulation index; lower bound of the estimate variance

Application of the Shack–Hartmann Wavefront Sensor for Monitoring the Parameters of a Supersonic Gas Jet by V. I. Trunov; K. V. Gubin; K. A. Ivanova; A. G. Poleshchuk; A. G. Sedukhin; V. V. Cherkashin (19-25).
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.
Keywords: gas jet; Laval nozzle; Shack–Hartmann sensor; wavefront analysis

Investigation of Computer-Generated Fresnel Holograms for Wavefront Sensors by V. I. Bobrinev; M. L. Galkin; M. S. Kovalev; P. I. Malinina; S. B. Odinokov (26-31).
The possibility of using computer-generated Fresnel holograms to determine phase aberrations of a wavefront is studied. The results of computer simulation of the propagation of an elementary signal based on the Fresnel integral transform are presented. The principle of operation of a hologram for a wavefront sensor is discussed.
Keywords: computer-generated hologram; wavefront sensor; phase aberrations; Fresnel hologram

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.
Keywords: nonlinear optical properties of saffron; Z-scan

Planar Phase Electro-Optical Modulator Based on Chromophore-Doped Polyimides by S. N. Atutov; S. L. Mikerin; A. I. Plekhanov; A. E. Simanchuk; V. A. Sorokin; A. V. Yakimansky; N. N. Smirnov; N. A. Valisheva (39-45).
Experimental studies of nonlinear optical and electro-optical properties of original synthesized chromophore-doped polyimides with a covalently attached DR-13 dye are reported. Second harmonic generation measurements are compared with the results of direct electro-optical response measurements by the Teng–Man technique. High temperature stability of the examined polyimides is observed. Methods of creating a planar phase electro-optical modulator with the use of synthesized chromophore-doped polyimides are designed and elaborated. The optical and electro-optical characteristics of the modulator are presented.
Keywords: electro-optical polymers; microwave photonics; electro-optical modulator; second harmonic generation; Teng–Man method

Stabilization of Astronomic Images Using a Controlled Flat Mirror by S. Yu. Bokalo; I. M. Bokashov; D. M. Lyakhov; S. V. Pikulev; A. V. Chernykh (46-51).
A prototype of a key element of adaptive-optics 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 value of 100 Hz was achieved for the bandwidth of a closed-loop system. The efficiency of the developed software was confirmed by daytime observations of stars.
Keywords: adaptive-optics system; atmospheric turbulence; wavefront; least-squares method; PD controller

Development of Telecentric Objectives for Dimensional Inspection Systems by E. S. Zhimuleva; P. S. Zavyalov; M. S. Kravchenko (52-60).
Features of designing objectives telecentric in the object space are discussed. The optical layout of three telecentric objectives developed for dimensional inspection systems using the shadow projection method is presented. A method for monitoring the quality of manufacture of such objectives having small distortion (less than 0.02 %) and small non-telecentricity (less than 0.01°) 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.
Keywords: telecentric objective; optical design; objective quality inspection; shadow projection optical method

Analysis of the Transmission Spectra of Optical Microcavities Using the Mode Broadening Method by D. D. Ruzhitskaya; A. A. Samoilenko; A. D. Ivanov; K. N. Min’kov (61-68).
This paper presents an algorithm for processing the transmission spectra of whisperinggallery optical microcavities for use as a nanoparticle detector. The algorithm is based on the broadening of the microcavity resonance curve during precipitation of nanoparticles on the microcavity surface. Experimental results on the detection of particles are compared with Langmuir adsorption theory. The contribution of the instability of the excitation radiation source due to the temperature drift of the resonant frequency to the measurement error is estimated.
Keywords: optical microcavities; optical sensor; nanoparticles; whispering-gallery modes; Langmuir adsorption theory

Non-Contact Triangulation Measurement of Distances to Mirror Surfaces by M. M. Mordasov; A. P. Savenkov; M. E. Safonova; V. A. Sychev (69-75).
Metrological analysis of triangulation laser sensors for measuring distance to mirror surfaces was performed. Theoretical and experimental studies have established that the measurement range of 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 non-contact sensor for measuring distance to liquid surfaces which provides signaling upon reaching a prescribed value is designed. An overview of triangulation measurement systems is given.
Keywords: triangulation systems; mirror surfaces; geometric parameters; distance signaling error

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 highquality classification of similarly looking types of vegetation by merely using training sets with the maximum degree of the pixel distribution over the image.
Keywords: remote sensing; hyperspectral image; classification of surface types; spectral and spatial features

Scalable Application for the Search of Global Minima of Multiextremal Functions by I. V. Bychkov; G. A. Oparin; A. N. Tchernykh; A. G. Feoktistov; S. A. Gorsky; R. Rivera-Rodriguez (83-89).
This paper describes the urgent issue of providing scalability of computations in the solution of multiextremal problems arising in different fields of scientific studies, including image processing. There is an approach proposed for the development of the Gradient scalable application for solving the problem of global optimization of multiextremal functions with account for a multistart method in the Orlando framework. An additional step of computations is implemented in the problem solving scheme, 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 are developed.
Keywords: distributed computing; scalable application; multiextremal functions

Goodness-of-Fit Test Based on Biinomial Probability Distribution by E. L. Kuleshov; K. A. Petrov; T. S. Kirillova; R. A. Khaliullin (90-96).
This paper describes the goodness-of-fit test based on binomial probability distribution, which reduces to a sequence of bilateral 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 test is evaluated by numerical modeling.
Keywords: goodness-of-fit test; interval estimate; probability distribution law; significance level

This paper describes the use of a cascade compensator constructed according to a Smith scheme in the forward loop of a system being designed for the purpose of analyzing the quality of processes in steady states. This can be effectively used to solve the problem of providing the system with a required reserve of stability by placing a dead-time element outside a closed loop. The dead-time effect manifests only when the transient time increases by the value of dead time with no changes in the overshoot value. It is determined that the velocity Q-factor of the system with a cascade compensator constructed according to a Smith scheme theoretically cannot be larger than the reciprocal of the dead time. This paper also demonstrates the possibility of reducing this negative property of the cascade compensator constructed according to a Smith scheme by dead-time pseudo-compensation with the use of differentiating elements.
Keywords: continuous plant; dead-time element; cascade compensator; Smith predictor; pseudo-compensation; synthesis algorithm

Influence of Turbine Wheelspace Temperature on Measurements of Radial and Axial Displacements of Blade Tips by S. Yu. Borovik; M. M. Kuteynikova; Yu. N. Sekisov; O. P. Skobelev (105-111).
This paper presents 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 currents, and with an ADC at the output. The circuit is designed as part of automation systems for tests of gas turbine engines. Methods for eliminating the temperature influences on the sensors using the hardware and software of the measurement system are considered. Using a model of the measuring circuit, we determined the families of conversion functions (dependences of the code on the desired radial and axial displacements) for normal and nominal temperatures and then, from their difference, the families of functions of temperature influence on code changes, which characterize possible errors. Quantitative estimates of the maximum values of the influence functions were obtained which confirm the efficiency of the proposed methods.
Keywords: turbine; complex-shaped blades; single-coil eddy current sensor; radial and axial displacements; methods for eliminating the influence of temperature on the sensor