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Problems of stability of bistable states in aspect of information storage are considered. Influence of temperature dependencies of absorption coefficient and relaxation time of free electrons onto realization of bistability and possibility of self-switching were investigated in context of a point-wise model. As a result various regimes of interaction of light pulse with the semiconductor were revealed due to the numerical simulation and parametrical analysis. Principal possibility of instability of both bistable states, which promote development of self- switching, was first shown in the model.
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We consider an optically bistable scheme based on growing absorption and equipped with an additional lateral feedback loop. Mathematical model of this device is proposed and analyzed. We demonstrate the simultaneous transfer to instability of steady states that belong to upper and lower branches of the bistable media characteristic curve. This stability loss may cause either self-switching of the scheme from one steady state to another or generation of autooscillations. The latter may be used for the formation of pulse sequences with given duration. We show that adding several loops instead of one sufficiently decreases the input intensity, necessary for switching. The role of diffusion processes in pulse formation is discussed, and the spatially non-uniformal stationary solutions are demonstrated.
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In our report a new type of optical bistability is proposed. It is based on a violation of Snell's law of inclined laser beam that is reflected from a mirror having a hole at its axis. We demonstrate switching of light power passed through the hole. Time of switching is less than 10-13 c. In our opinion, this scheme has very good characteristics for creation of its base the optical switching element with very short time of switching and low energy of switching since we use refractive properties of medium.
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Bragg acousto-optic interaction in isotropy media is considered. The basic idea of this diffraction is grounded on the splitting the incident two-color light into two separate beams due to Snell's law and the fitting the Bragg synchronism for every beam and a single acoustic wave. Two variants of such diffraction are possible: diffracted beams propagate at one side respect to the incident beam, and they propagate at opposite sides respect to incident one. We have shown that the first variant is preferable for applications because of better fulfilling of Bragg diffraction conditions.
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A novel scanner 3D display with special hologram transparent is proposed. 3D scene volumetric description with irregular depth coordinate is used in this system. This approach decrease sharply demands for the information flow of dynamic 3D scene describing. The hologram transparent consists on 3K layers, where every layer corresponds to resoluted 3D scene depth plane and R, G, B colors. Every hologram layer maintains only one hologram.
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In colorimetry, photoelectric and spectral methods are used for color coordinate measurements. The spectral methods are based on measuring the spectral characteristics of optical beam and successive calculation of color coordinates. They provide better measurement accuracy comparing with the photoelectric methods as they implement the spectral functions of color mixing more accurately.
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Acoustoelectronic and Acousto-optic Signal Processing
The paper presents results on theoretical and experimental investigation of a tunable acoustic-optic filter designed with the goals of applications in optics and spectroscopy for spectral filtration of divergent RI optical beams and images. Physical principles of operation of the wide-angular acousto-optic filter are examined and basic parameters of the developed instrument are described in the paper. The device was fabricated on base of a specially chosen crystal cut of optically anisotropic tellurium dioxide single crystal. Optimization of the filter parameters resulted in development of the instrument combining low driving power with high spatial and temporal resolution. Experimental block-scheme of filtration and optical setup for image processing are described in the report and some peculiarities of the imaging experiments in the middle IR region of spectrum are discussed in the paper.
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This paper is devoted to analysis of acousto-optic Bragg diffraction in tellurium dioxide single crystal in case of bulk slow shear ultrasonic waves propagating in the material. The so-called 'isotropic' type of the diffraction by the acoustic wave is examined in the paper. Contrary to the well known 'isotropic' diffraction, the investigated acousto-optic interaction is characterized by conservation of initial optical mode int he crystal. It is proved that the discovered regime of isotropic interaction in an anisotropic material is similar to interaction in optically isotropic media. The paper acquaints with equation representing dependencies of Bragg incidence angles on acoustic frequency in the crystal. The derived equations are different from the known equations in isotropic media. Experimental results on measurements of frequency dependencies of Bragg incidences angles in paratellurite are presented in the paper. Peculiar dependencies of diffraction efficiency on amplitudes of acoustic waves are also discussed in this paper. Peculiar dependencies of diffraction efficiency of the examined isotropic interaction may be higher than the efficiency of the anisotropic scattering. As proved experimentally, maximum diffraction efficiency values for the investigated isotropic diffraction in tellurium dioxide may exceed 60 percent.
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The influence of acoustic field amplitude inhomogeneity on the transmission function from in an AO cell is investigated in present paper. It is shown that the decrease of the acoustic field on input and output of the crystal results in diminution of the first and the second side lobes level of the AO cell transmission function. According to the results calculated, the acoustic field amplitude alteration in the regions symmetrical relative to the crystal center equally affects the AO cell side maxima level. The symmetric distribution of the transmission function left and right side lobes remains intact at any alteration of an acoustic field. The distortion of this symmetry occurs when allowing for an acoustic field phase shift. The propositions mentioned above make it possible to drive the AO cell transmission function inside lobes level. The presented example of an acoustic amplitude distribution along the optical propagation direction demonstrated the substantial side lobes level suppression.
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The present work aims at understanding how preparation of liquid crystal layers with rod-like molecules influences their transient nonlinear response to nanosecond laser radiation.
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Demultiplexer is the key component of wavelength division multiplexing systems of telecommunications. This paper deals with theoretical investigation of temperature influence on fiber Bragg grating (FBG) based demultiplexes characteristics. At current moment FBG based demultiplexes are most advanced devices on market. In this paper, we describe and characterize a high performance wavelength demultiplexing devices based on a fiber Mach-Zehnder interferometer with photoinduced Bragg gratings in the interferometer arms and simple all-fiber demultiplexes based on single FBG with out-coupling of radiation from the fiber core. The values of wavelength channels shifts versus temperature are calculated for both types of demultiplexes.
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Acousto-optic tunable filters (AOTF) have found their area of application mostly related to spectrum analysis of different media in environmental studies. However, the AOTF ability to select the particular color from multicolor incident light beam can be used in the light projection system. As acousto-optic devices based on the same Bragg cells can both select color and deflect the beam, it is possible to perform the projection of different color images. Some configurations of such systems has been discussed in the presented paper. It has been shown that one of the most important parameters defining the system ability to form color images of good quality is information transmission capability of al the system and of its components as well. It is especially related to acousto- optic components: AOTF, modulators and deflectors. The signal transmission through the proposed system has been considered for some versions of its implementation. Along with that the possible amount of information which can be transmitted simultaneously through the system, has been considered, and the links of the system which can limit the total information transmission, have been found. In conclusion, separate problems that could be solved using the projection systems composing different acousto-optic devices including AOTF, have been defined.
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A new technique is developed to image IR sources by holography using a binary Gabor zone plate. The hologram consists of superimposed shadows of the binary Gabor zone plate cast by IR sources. The reconstruction is carried out by using Fast Fourier Transforms. The scaling produced by the zone plate encoded technique is indicated and a correction for this can be easily made using a computer. In this way, a true IR image in 3D can be obtained.
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Some principles of 3D visualization are analyzed in this paper. A novel scanner system with special hologram transparent for 3D visualization is proposed. Volumetric principles are utilized in this system. 3D Cartesian coordinates with irregular scale in depth direction are possibly used for 3D objects describing. This approach decrease sharply demands for the information flow of dynamic 3D scene describing.
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The optical heterodyne correlator (OHC), in which the functions of overlapping and fast scanning by reference image relatively signal image and light frequency shift between them are realized with the hologram lens scanner (HLS) in JFT plane is described. The important advantage of this scheme is that any phase distortions of amplitude spatial filters (ASF) inserted in the imaged JFT plane do not affect output response. That provides high instrumental accuracy of OHC and wide possibilities for adaptive processing with using controllable ASF and matrix photodetectors. Presented results of experiments demonstrate high performance of this scheme. Multichannel fiber optical communication between the imaged JFT plane of OHC scheme and elements of radio antenna array permits fast and soft beam forming and scanning by computer controlled optical transparencies and HLS.
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The optical grating has been the subject of extensive, sustained research for many years. Field of their application include integrated optics, quantum electronic, holography, and spectroscopy. Grating functions include laser-beam feedback, distributed Bragg reflection, holographic beam combining, wavelength multiplexing, wavelength de-multiplexing, and others. Another interesting object of modern physical research is a layer of a resonant plasma (LRP) in which if the charge equilibrium of this system is distributed, the electron gas performs density oscillations, the so-called plasma oscillations and the complex refractive index of which is described by Dride's formula. It is the purpose of this work to combine this two interesting physical objects and investigate the process of the light diffraction by dielectric grating which enclose LRP. We researched Ge-grating on GaAs-substrate under the service of conversion almost vertically incident light into quasi-horizontally propagating light inside the substrate. It is common knowledge that process of conversion almost vertically incident light into quasi-horizontally propagating light is very interesting from the practical standpoint for many cases for example for introduction of light into different optical structure. In our investigation LRP was placed both in the Ge-grating region and in the region of GaAs-substrate.
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The influence of ambient temperature at the performance of the acoustooptical spectrum analyzer as well as middle IR optoelectronic gas analyzer are studied. The measurements were carried out with the help of developed temperature stabilizing module utilizing thermoelectric Peltier element and temperature sensors LM 45 within the operation temperature range stabilizing with the accuracy of +/- 0.1 degrees C.
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We demonstrate experimentally and theoretically that the sign of two-wave coupling gain in sillenite crystal at some polarization of light changes with the increase of the amplitude of square-wave field applying along the axis. It is shown that the nonunidirectional energy exchange is the reason of this effect in Bi12TiO20 single crystal. Also strong influence of this effect on the polarization properties of the two-wave coupling gain was it revealed at the experimental investigations of the efficiency of the two-wave interaction in Bi12SiO20 single crystal. At the theoretical analysis we used the model obtained on the basic of the mode approach. Made the numerical calculation of dependencies of the two-wave coupling gain has good agreement with the experimental data. This calculation has allowed estimating the material parameters of the investigated samples of the crystal.
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It is known that localized elastic and electric fields appear near the surface of piezoelectric crystals under photorefractive grating information.
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The influence of CCD charge transfer inefficiency on the AO processor output signal is considered in this report. The impulse characteristic for scanning CCD is derived. It is shown that clock frequencies can be approximately twice as large than the case of usual mode of CCD.
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The waveguide conception of construction of optical integrate circuits to implement vector - matrix transform is discussed. The realization of such circuit is considered as multilayer structure whose basic components are the controlled waveguide diffraction beamsplitter and the waveguide diffraction beam integrator with buffer layer. Construction and fabrication technology of circuit components is presented. Optimal sizes of diffractive element of beamsplitter and integrator are defined. Possible applications are shown.
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Carried out recently theoretical and the experimental researches have shown an opportunity of effective transformation optical guided-waves of styles in epitaxial YIG film at interaction with MSW.
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The basic opportunity of bistable dependencies of medium temperature and vibrational energy of molecules on heat conduction parameter and on normalized VT-relaxation time is shown for light energy absorption at non-ground vibrational levels. Practical realization is possible, particularly, by usage of elliptically defocused beams. As a result there is anew opportunity to form high temperature domains in the any section of medium, using defocused light beams. The bistability property, discussed within the framework of the point model, is confirmed by modeling of a light pulse propagation in optically non-uniform vessel with molecular gas.
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This work presents the computer program simulator of acoustooptical electronic processors (AOEP). The basic parts of the AOEP are optical processor and multielement photodetector, which are represented by there multiparameters models. This processor is used in dispersion compensator of radiosignals from pulsars. The simulator can be used for studying the methods of radiosignals processing by AOEP in education.
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The structure and operating principle of an hybrid optoelectronic system is presented. The basic part of the system is digital signal processor. DSP executes functions: control, synchronization, data processing. The construction two systems with DSP: AO radiospectrometer and AO dispersion compensator of radiosignals from pulsars are discussed.
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Experimental results of the study of nonlinear propagation of phase conjugated ultrasonic beam in water are presented. Time waveforms were measured using spectral analysis of light diffraction by the sound field, which permits digital acquisition of signal pulses. Data processing and analysis were carried out in approximation of Raman-Nath conditions. For high intensity ultrasound the method based on direct connection between amplitude of Raman-Nath spectra and Fourier components of ultrasonic wave was developed.
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Acousto-optic deflectors play an important part in holographic memory devices (HMD). However, these deflectors not only expand the HMD possibilities but also introduce some limitations related to the maximum amount of information to be stored as well as to the rate of information retrieval. These limitations are the subjects of the consideration in the presented paper.
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One of the most important metrology problems is a problem of velocity measurement /1/. Laser Doppler anemometry permits to solve this problem by means of the non contact method. The essential advantage of this method is a high measurement accuracy and space localization. In the laser Doppler anemometry dispersion of optical energy on reasonably large particles is used. The applications of given method has essential restrictions, especially at a high enough velocities and considerable turbulence of the flow. In this case speeds of the particles does not correspond to the flow velocity. An other problem is that reasonably large particles disturb a flow structure. Therefore when the flow velocity is commensurable with the velocity of the acoustic wave or the turbulence of the flow is essential, the probability of measurements becomes questionable. To terminate these limitations the employment of the molecular dispersion phenomenon in the laser Doppler anemometer creation was offered. This method doesn't demand the existence of the dispersion particles in the flow. The dispersion centers are formed because of the thermal molecular displacement. The spectrum of the dispersed optical radiation has three frequency components. The first one comes into existence at the same wavelength with the probe optical radiation, but contain reasonably large number of molecules. Obviously, in the ideal medium without any optical impurities should be no dispersion of optical radiation, as the radiation dispersed by the various elementary volumes will be equal. However in any really existing medium an optical impurities are present, they are stipulated by the thermal chaotic movement.
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Acoustooptic matched filter is capable of processing short, wideband chirps. But due to generating process peculiarities, middle frequency, slope and convexity of instant frequency function are fluctuating. To implement electronic tuning of impulse response, AOMF architecture was completed with controllable liquid-crystal phase mask. The paper presents mathematical models for both fluctuating chirp signal and tunable acousto-optic matched filter. Adaption algorithm was developed for impulse response matching with parameters of chirps being processed.
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The work was devoted to optimization of time integrated acoustooptical correlators (TIAOC) parameters. To increase time bandwidth product acoustooptical properties of nontraditional cuts for lithium niobate have been investigated. The cut for SAW velocity direction has the most wideband diffraction efficiency. During the work influence of laser diode aperture function, optical path losses, units position accuracy on TIAOC dynamic range has been investigated. Special software gave the opportunity to calculate value of each factor in total TIAOC dynamic range. Computer simulation results of the TIAOC showed the laser diode aperture function in total TIAOC dynamic range. Computer simulation results of the TIAOC showed the laser diode aperture function non-uniformity and optical path losses decreased TIAOC dynamic range up to 12 dB. Optical elements position accuracy for the TIAOC experimental sample was analyzed with the special simulation computer program. The program simulates the device correlator function. The CCD position exactness is about 2.5 mm.
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The results of theoretic research a matrix-vector multiplier on base acoustooptic filter with 2D liquid-crystal reference mask are brought in report. Dependencies of dynamic range from real parameters of scheme are presented and analyzed. Also relationship between dynamic range and probability of error on symbol is determined.
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Performance analysis for the space-integrating acousto-optic correlator based on optical interference with external noise and allowance for shot noise of photodetector is presented. Signal-to-noise ratio and dynamic range are obtained in the general form, the results in the graphical form are also presented.
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This paper is devoted to investigate the multiple acoustoelectronic processors on surface acoustic waves intended for spatial signal processing of antenna arrays. Theoretically and experimentally influence of substrate anisotropy and correlation of microaperture devices of a reradiating arrays of the processor on its output characteristics is investigated.
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Optical waveguides on ion-exchanged SiO2 glass are perspective for monolithic optical-integrated schemes due to low optical losses, high temporal stability of their parameters, big sizes, low cost, high optical quality. The creation of efficient AO deices on non-piezoelectric substrate is rather difficult because of the necessity of film piezoelectric transducers fabrication, of secure SAW input in optical waveguide and of low AO quality coefficients of commercial glasses.
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Theoretical analyses, computing simulation and designing for planar acoustooptical devices has been made. Original manufacturing technology for the devices has been done. The device parameter measurement and control has been designed and produced. Several modifications of a planar acoustooptical deflector, an integrated optical RF spectrum analyzer, a planar acoustooptical frequency modulator, a time integrating acoustooptical correlator and an integrated acoustooptical optical radiation spectrum analyzer, a multichannel RF receiver have been produced and investigated at Institute for High Performance Computing Systems of Russian Academy of Science.
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One of problems of high resolution acousto-optic tunable filters (AOTF) design and manufacture is to make an acousto- optic cell with a large length of interaction. The traditionally used cells on an orthogonal diffraction have a disadvantage that their interaction length is determined by the size of the piezoelectric transducer. In addition, a large transducer has a high capacity and small radiation resistance, which is extremely inconvenient. Therefore, in this case, segmented transducers usually are used. However, such partitioning results in more complex AOTF construction and matching of the piezoelectric transducer with an RF signal generator.
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A numerical analysis of the surface acoustic waves (SAW), Leaky surface waves has been performed. A method of search for SAW and Bulk waves in crystals is based on the Farnell's technique. A method of search for leaky waves in crystals is based on the calculation of permitted orientations for exceptional bulk waves, which satisfy the stress-free boundary conditions for surface waves. A search for leaky waves is based on the calculation of the Global Extremum of complex boundary condition function, depending on many variables, over the regular grid in combination with local search by Hooke's and Jeeves' method of configurations and by Mugel's procedure in the ravin domains. The optimal characteristics have been found for leaky waves: velocity V, electromechanical coupling coefficient K2, the power flow angle PFA0, attenuation loss (alpha) , the temperature coefficient of delay in LiNbO3, LGS and LGN crystals.
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In this paper, theoretical investigation is shown for cuts and propagation directions on KNbO3, PKN substrates where the Bleustein-Gulyaev waves exist. The KNbO3 and PKN crystals Y-cut X-propagating relate to the condition in which the stiffened shear horizontal wave and pure mechanical Rayleigh wave are present. In this symmetry orientation the sagittal and transverse particle displacements also uncouple. In this situation, the potential is coupled to the shear horizontal displacements only. Electromechanical coupling coefficients K2 has a sufficiently large value of above 53 percent with a phase velocity of V equals 3.918 km/s for KNbO3 crystals and factor K2 has a large value of above 23.6 percent and phase velocity V equals 3.054 km/s for PKN crystals.
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Power spectrum measurements by diffractional methods with classical and quantum description of electromagnetic signals are considered. Classical aspects of spectral measurements (SM) theory is based on classical approximation of exact quantum representation of signal and spectrum analyzer (SA) description in terms of linear system theory. Quantum aspect of SM theory considers SM process as transformation temporal statistics of photons to their space distribution statistics, performed by SA.
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The experimental investigation of the problem of collinear acousto-optic tunable filters driven by successive variable acoustic pulses is carried out. It is shown that in the case of acoustic pulse of a stepped from the substantial suppression of the transmission function side lobes can be observed. The influence of the acoustic pulses number situated in the crystal simultaneously and their duration on the collinear filter apparatus function was investigated. It is found that in this case the apparatus function consists of a number of a narrow peaks and the distance between them depend on the number of pulses in crystal, while the number of peaks depends on the each acoustic pulse duration. The investigation of spectrum consisting of tow close lines was carried out with a help of collinear acousto-optic tunable filter.
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A spectrum analyzer of optical signal based on an acousto- optic tunable filter (AOTF) is a sequential analyzing system where the scanning along the wavelengths is made by varying the control signal frequency. Traditionally, a chirp control signal is used in such systems, provided that the frequency variation rate in the cell's acoustical aperture is negligibly slow. In this case, the system spectral response replicates the amplitude frequency response of acousto-optic interaction. However, when the system speed are to be maximized, the frequency variation rate in the cell aperture has to be taken into account. Basing on the linear system theory, the paper presents the calculation of the spectrometer's output signal for a laser input optical beam, weak interaction approximation, and chirp RF control signal. The closed form equation is obtained using the stationary phase method. Basing on the obtained expression, the minimally possible time of analysis is obtained for the spectrometer based on the AOTF with the quasi-collinear interaction in the TeO2 crystal. The criterion was the 10 percent decrease in spectral resolution. The experimental results are in good agreement with the theoretical predictions.
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The algorithm of cross-correlation function (CCF) evaluation, by means of a reverse Fourier transformation above the mutual spectrum of signals, is widely known. The evaluation of mutual spectrum is carried out as a result of execution of Fourier transformations above the input signals and subsequent complex multiplication of Fourier- transformations results. The evaluation of a mutual spectrum in acoustooptics at usage of two Bragg-cells is impeded. For CCd evaluation on sectional algorithm the combination of acousto-electronic chirp-transformations of input signal with subsequent acoustooptical multiplication of signal spectrums and the execution of a reverse Fourier-transform is expedient.
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There is a whole class of spectral devices for light sources' emission spectral analysis. By analysis of a such type spectra of extended light sources the procedure of scanning the source surface is usually applied. The methodics on extended light sources' emission spectral analysis based on the correlation processing the space and spectral parameters is offered. As input object in the correlator the complex extended scale-invariant mask was used. The use of this mask allows to exclude a procedure of scanning the source surface by analysis. As a resolution element of such spectral analyzer the located spatial autocorrelation signal of the input mask is used. The experimental scheme of correlation spectral analyzer is created. The output plane calibration of the device with the light spectral structure to be determined is conducted. The results on extended light sources' emission spectral analysis are described. In experiments the spectral resolution of the device is determined as 1 nm. The use of such spectral analyzer allows to construct system of the spectral analysis with large speed without application of scanning devices.
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In optical information processing systems with partial and even completely of destroyed space coherence radiation, the technique of transformation of space coherence degree appears rather effective for want of creation reliable devices, capable to work in real time scale. It is represented perspective for want of to development of functional of optical information processing systems, including stages of pick up, transfer, storage, imaging to use as a main principle of construction a light field creation method with specific coherent properties. The outcomes of researches of possibility of optical sensor are resulted, in which as a disturbance value criterion the qualitative measurements of coherent properties of radiation in correlation with changes in geometrical parameters of the system is considered. The otpical system is created which can be considered as the fiber-optical sensor of mechanical disturbances of a vibrational type. The adjustable sensitivity of registration is achieved when the redistribution of a destruction level of light space coherence in an input of the system and a site of transfer of light signal. Is shown, that relative accuracy are 10-3. The developed approach to creation of measuring system based on transformation, visualization and measurement of light space coherence changed in the communication line with natural or artificially created nonstability can find application for want of construction of location optical systems, altimeters working in actual conditions, and also for measurement system for oscillating disperse surfaces.
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The compact scheme of the incoherent holographic correlator with two-coordinate acoustooptic deflector (AOD) for input of recognized images is presented. Because AOD forms an input image as a sequence of dynamic diffraction gratings, it allows to put a holographic filter directly in the place where AOD is situated. The experimental setups of the correlator with holographic memory and monochromatic illumination are described. Experimental results on recognition of test objects with two different illumination sources are presented. The correlation signals for setups with He-Ne laser and semiconductor laser are coincide within the limits of experimental errors. The result obtained show that both experimental setups of the incoherent holographic correlator provide real-time recognition of input images formed by two-coordinate acoustooptic deflector.
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The optical-electronic image formation lensless system based on spatial coherence transform and nonstationary wave fronts integral registration of distant objects is described. The image formation process in this system can be interpreted as a double Fourier transform: primary Fourier transform performs in optical channel and following reverse Fourier transform - in optical-electronic channel by means of wide aperture photodetector.
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Surface acoustic wave (SAW) resonators are one of the rapidly developed classes of acoustoelectronic devices. Today SAW resonators and resonator filters play a key role in modern mobile communication systems. The main advantages of these filters are small size, low cost, high reproducibility. Besides resonator filters allows permit low insertion losses and long pulse response on small substrate.
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Zone plate holography is a way of obtaining 3D images from a single exposure. Unlike conventional holography, coherent radiation sources are not required. Gama ray zone plate holography can be used to image gamma rays emitted by radiopharmaceuticals used in nuclear medicine. This work concerns the computer based reconstruction of gamma ray holograms. Reconstruction algorithms including correlation and Wiener filtering are described. The images obtained using the different methods are compared.
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We present and demonstrate a novel proof-of-principle system with parallel optical input/output to perform mathematical morphological operations on discrete gray level images. Experimental results of erosion and dilation of 8 by 8 images are presented, as well as threshold decomposition of a 6-gray level image into series of binary slices.
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A great research effort has been spent in recent years for the use of guided-wave optoelectronic technologies for signal processing in space applications, because they allow to reduce size, weight, power consumption and system complexity with respect to electronic ones. Based on these motivations, we have conceived, designed and simulated a number of original integrated optical signal processors, such as 2D correlators for imaging reconstruction in SAR applications, both airborne and spaceborne, preprocessors for data classification and identification in satellite applications for remote sensing, beam formers and steerers in active phased array antennas, heterodyne spectrum analyzers, and so on. The substrate materials considered for these circuits are both ferroelectric and III-V semiconductor materials. Original modeling and numerical techniques have been developed to analyze and design the guided-wave components included in the optical architectures. In this paper, the most significant developments of this research activity are reviewed.
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The light scattered back form a scattering medium is expected to carry the range information about the reflective boundaries and backscattering sites in the medium as well as the information about their spectral reflectance. We suggested a white-light interferometry technique and signal processing algorithm for the retrieval of this kind of integral information from scattered light called coherence spectrotomography. The coherence spectrotomography is a version of low-coherence interferometry that enables us to extract both range and spectral properties inside a medium simultaneously. The white-light continuum is a new type of a broad-band and bright light source that is suited for the coherence spectrotomography. We generated the array of the white-light continuum by directing a microlens array into ultrashort laser pulses into water through a microlens array. We present our experimental results related to the coherence properties of the white-light continuum and its applications to coherence spectrotomography of a colored layer of semitransparent medium.
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