Статьи журнала - Компьютерная оптика
Все статьи: 2382
Computer controlling of writing beam in laser microfabrication of diffractive optics
Статья научная
Laser microfabrication of diffractive optics with continuous relief is based on the direct local action of focused laser radiation on the recording material. Control of writing beam parameters (beam power, spot size, waist position) is one of the main tasks in microfabrication using laser writing systems. Method of the control defines the correspondence between the fabricated microrelief of the diffractive optical element and a designed one. Complexity of this task consists in the necessity to take into account a wide range of factors: laser irradiation noises, non-linear characteristic curve of recording material, finiteness of spot size, influence of power modulation and surrounding on beam energy absorption, influence of beam waist position according to recording layer, dependence of characteristic curve of recording material on beam scanning speed, etc. In the present paper we consider a number of methods for computer controlling of writing beam making it possible to compensate or reduce the influence of these factors and improve the quality of DOE microfabrication. The results of experimental application of the developed methods to circular laser writing systems are discussed.
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Computer generated microwave kinoforms
Статья научная
Reflective computer-generated holographic elements are used in a quasi-optical fashion to modify both the phase and polarisation of a high-power coherent microwave beam. Theory and desigh for both one and two component systems are discussed as well as some experimental results.
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Computer optics and its development
Статья научная
The article consider prospects of the future development of the Computer Optics and its interrelation with the computer and optic sciences including the optical softwere and hardwere field, photon computer science.
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Conditions of a single-mode rib channel waveguide based on dielectric TiO2/SiO2
Статья научная
In this paper, we propose conditions for the design of a single-mode rib channel waveguide based on dielectric materials such as titanium dioxide (TiO2) and silicon dioxide (SiO2) for the 0.633-µm visible light. We also design Y-splitter structures, which show high-degree optical confinement and low bend losses at various radii of curvatures. Small radii of curvatures are extremely desirable in integrated photonics as they permit decreasing the dimensions but can also potentially reduce power consumption in the active devices.
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Conforming identification of the fundamental matrix in the image matching problem
Статья научная
The article considers the conforming identification of the fundamental matrix in the image matching problem. The method consists in the division of the initial overdetermined system into lesser dimensional subsystems. On these subsystems, a set of solutions is obtained, from which a subset of the most conforming solutions is defined. Then, on this subset the resulting solution is deduced. Since these subsystems are formed by all possible combinations of rows in the initial system, this method demonstrates high accuracy and stability, although it is computationally complex. A comparison with the methods of least squares, least absolute deviations, and the RANSAC method is drawn.
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Constraints for Jaccard index-based rotational symmetry focus position in binary images
Статья научная
This study proposes analytical estimate for the size of a binary raster figure region which is guaranteed to contain the rotational symmetry focus. Focus here is the point a maximum Jaccard index between initial figure and rotated one. The size of the region is determined by the lower estimate of the intersection area during the rotation of the approximating primitives, considering the sizes of the inner and outer parts of the figure relative to the primitive. The smallest circumscribed circle or ellipse and sets of concentric circles and ellipses produced by the principal component analysis were used as the approximating figure. To verify the hypothesis that the size of the region is insignificant compared to the area of the figure, we numerically simulated the proposed method with test image datasets.
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Copy move forgery detection using key point localized super pixel based on texture features
Статья научная
The most important barrier in the image forensic is to ensue a forgery detection method such can detect the copied region which sustains rotation, scaling reflection, compressing or all. Traditional SIFT method is not good enough to yield good result. Matching accuracy is not good. In order to improve the accuracy in copy move forgery detection, this paper suggests a forgery detection method especially for copy move attack using Key Point Localized Super Pixel (KLSP). The proposed approach harmonizes both Super Pixel Segmentation using Lazy Random Walk (LRW) and Scale Invariant Feature Transform (SIFT) based key point extraction. The experimental result indicates the proposed KLSP approach achieves better performance than the previous well known approaches.
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Crop growth monitoring through Sentinel and Landsat data based NDVI time-series
Статья научная
Crop growth monitoring is an important phenomenon for agriculture classification, yield estimation, agriculture field management, improve productivity, irrigation, fertilizer management, sustainable agricultural development, food security and to understand how environment and climate change effect on crops especially in Russia as it has a large and diverse agricultural production. In this study, we assimilated monthly crop phenology from January to December 2018 by using the NDVI time series derived from moderate to high Spatio-temporal resolution Sentinel and Landsat data in cropland field at Samara airport area, Russia. The results support the potential of Sentinel and Landsat data derived NDVI time series for accurate crop phenological monitoring with all crop growth stages such as active tillering, jointing, maturity and harvesting according to crop calendar with reasonable thematic accuracy. This satellite data generated NDVI based work has great potential to provide valuable support for assessing crop growth status and the above-mentioned objectives with sustainable agriculture development.
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Cross-layer optimization technology for wireless network multimedia video
Статья научная
With the development of communication technology, wireless Internet has become more and more popular. The traditional network layered protocols cannot meet the increasingly rich network services, especially video. This paper briefly introduced the cross-layer transmission of video in wireless network and the cross-layer optimization algorithm used for improving video transmission quality and improved the traditional cross-layer algorithm. Then, the two cross-layer algorithms were simulated and analyzed on MATLAB software. The results showed that the packet delivery rate, peak signal to noise ratio and downlink throughput of the improved cross-layer algorithm were significantly higher than those of the traditional cross-layer algorithm under the same signal to interference plus noise ratio of receiving users in wireless network; meanwhile, with the increase of signal to interference plus noise ratio of the receiving user, the packet delivery rate and peak signal to noise ratio of the two algorithms increased, and tended to be stable after some signal to interference plus noise ratio, while the throughput of the two algorithms increased linearly. In the established real wireless network, the package delivery rate, peak signal to noise ratio and throughput of video after application of cross-layer algorithm were significantly improved, and the wireless network applying the improved cross-layer algorithm improved more. In summary, compared with the traditional cross-layer algorithm, the improved cross-layer algorithm can better improve the transmission quality of video in wireless network.
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Статья научная
The work is devoted to an overview of the current state of optoacoustic fiber-optic ultrasonic transducers based on thermoelastic effect and fiber-optic interference receivers, its scope, technologies and materials used, the advantages and disadvantages of different methods and the prospects for the development of the industry.
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Cравнение разных подходов к формированию «идеального» оптического вихря
Статья научная
Получены точные аналитические выражения, описывающие комплексную амплитуду идеального оптического вихря, сформированного тремя разными оптическими элементами: амплитудно-фазовым с пропусканием, пропорциональным функции Бесселя, оптимальным фазовым с пропусканием, равным знаковой функции от функции Бесселя, и вихревым аксиконом. Показано, что интенсивность света на кольце больше для оптимального фазового элемента. Ширина светового кольца, сформированного вихревым аксиконом, примерно в два раза больше, чем ширина двух других колец. Таким образом, оптимальный элемент является наилучшим кандидатом для формирования идеального оптического вихря. Результаты моделирования подтверждают теоретические выводы, а результаты эксперимента согласуются с теорией и результатами моделирования.
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Data mining of corporate financial fraud based on neural network model
Статья научная
Under the active market economy, more and more listed companies emerge. Because of the various interest relationships faced by listed companies, some enterprises which are not well managed or want to enhance company’s value will choose to forge financial reports by improper means. In order to find out the false financial reports as accurately as possible, this paper briefly introduced the relevant indicators for judging the fraudulence of financial reports of listed companies and the recognition model of financial reports based on back propagation (BP) neural network. Then the selection of the input relevant indexes was improved. The improved BP neural network was simulated and analyzed in MATLAB software and compared with the traditional BP neural network and support vector machine (SVM). The results showed that the importance of total assets net profit, earnings per share, cash reinvestment rate, operating gross profit and pre-tax ratio of profit to debt was the top 5 among 20 judgment indexes. In the identification of testing samples of financial report, the accuracy, precision, recall rate and F value all showed that the performance of the improved BP neural network was better than that of the traditional BP network and SVM.
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Статья научная
The purpose of research to create automated personalization of diabetic macular edema laser treatment. The results are based on analysis of large semi-structured data, methods and algorithms for fundus image processing. The technology improves the quality of retina laser coagulation in the treatment of diabetic macular edema, which is one of the main reasons for pronounced vision decrease. The proposed technology includes original solutions to establish an optimal localization of multitude burns by determining zones exposed to laser. It also includes the recognition of large amount of unstructured data on the anatomical and pathological locations' structures in the area of edema and data optical coherent tomography. As a result, a uniform laser application on the pigment epithelium of the affected retina is ensured. It will increase the treatment safety and its effectiveness, thus avoiding the use of more expensive treatment methods. Assessment of retinal lesions volume and quality will allow predicting the laser photocoagulation results and will contribute to the improvement of laser surgeon's skills. The architecture of a software complex comprises a number of modules, including image processing methods, algorithms for photocoagulation pattern mapping, and intelligent analysis methods.
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Статья научная
We propose and numerically verify a design of the photonic integrated circuit for in-plane generation of a 1st azimuthal order vortex mode in dielectric rectangular waveguides. Radiation is introduced into the proposed structure in a standard way through two grating couplers. Applying a mode coupling and specific phase shift, a field with the required amplitude-phase distribution is formed directly in the output waveguide. The geometric dimensions of the device are simulated and optimized to fit the technological parameters of the silicon-on-insulator platform.
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Design and optimization of high-contrast gratings for multispectral VCSEL-SOI laser sources
Статья научная
In the scope of a computational experiment, high-contrast gratings (HCG) formed on a silicon-on-insulator (SOI) platform within vertical-cavity surface-emitting lasers (VCSELs) were studied for multispectral laser sources. A simulation model for spectral characteristics calculation is proposed, which includes two heterogeneously integrated parts of the VCSEL: 1) the lower output mirror based on a HCG grating in the silicon layer of the SOI surrounded by air cavities to enhance the contrast of the HCG; 2) the semiconductor VCSEL structure with an air aperture for current and optical confinement. Comparative analysis results of the spectral characteristics of VCSEL-SOI structures for zeroth, first, and second-order modes, which can be excited in the air aperture of the VCSEL, are presented. It is demonstrated that the HCG, acting as one of the cavity mirrors, effectively discriminates the VCSEL higher-order modes. An algorithm for calculating HCG parameters that ensure the maximum reflectivity at a fixed thickness of the silicon layer of the SOI is developed.
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Статья научная
The paper proposes a new architecture for the photonic laboratory-on-a-chip sensing systems, where multiple sensors based on microring resonators (MRR) are fed by a MRR with low quality factor, working as a spectrum shaper. This architecture enables simultaneous intensity scanning of at least four MRR-based sensors on the silicon-on-insulator platform. We evaluated numerically the system’s sensitivity for various schemes of connecting the sensors and the spectrum shaper. The sensor’s sensitivity was 110 nm/RIU. The sensing system configuration largely determines its sensitivity, which reaches 1980 dB/RIU. The considered architecture may be useful for implementing fully integrated optical lab-on-a-chip structures, as well as distributed multichannel sensing systems.
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Design of lenses for the focusing into a line
Статья научная
A method for designing a curvilinear lens for focusing into a line is proposed. The obtained solutions represent a complex refracting surface in an analytical form expressed through the eikonal distribution along the line. The calculation of a 3-D lens focusing into a line-segment is reduced to a simple design of cylindrical profile with required function of ray-correspondence.
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Design, simulation, and fabrication of silicon-on-insulator MEMS vibratory decoupled gyroscope
Статья научная
This paper reports the design and fabrication of a 2-degree-of-freedom (DOF) decoupled vibratory gyroscope based on a silicon-on-insulator (SOI) MEMS process. The 2-DOF capacitive comb structure is deliberately designed to have a decoupled drive and sense mode oscillation to prevent the unstable operation due to mechanical coupling, resulting in a low zero rate out-put drift. It is well known that the closer are the drive and sense resonances, the higher is the angular rate resolution of the gyroscope. Generally, this is achieved by using symmetric suspensions, but it results in a reduced bandwidth. The proposed design has been configured to achieve a bandwidth of about 150 Hz, while ensuring the decoupled operation of the drive and sense modes. An analytical method has been employed to study the steady state response of the 2-DOF structure. FEM analysis has been carried out in CoventorWare® MEMS Design software and the simulation results show that the drive resonance occurs at 21.48 kHz and sense resonance at 21.63 kHz, which are in close agreement with the theoretical results. The structure is designed with a 15 µm thick device layer. Fabrication of the design is proposed using a two mask process based on Deep reactive-ion etching (DRIE) and sacrificial wet release etching on a SOI wafer. DRIE etching with an aspect ratio of 1:5 has been successfully carried out as desired and the results have been presented.
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Designing multilayer dielectric filter based on TiO2/SiO2 for fluorescence microscopy applications
Статья научная
This study presents a new construction design of a distributed Bragg reflector (DBR) filter and a Fabry-Pérot (FP) filter by using needle technique as a synthesis method. The optimized DBR and FP filters having a proper number of layers with controlling thickness TiO2/SiO2 are utilized to transmit only a certain narrow band of wavelengths while blocking the others. As a proof of concept, the filters are designed to selectively transmit only a very narrow band of wavelength at 780 nm which is the near infrared (NIR) fluorescent emission from Alexa Fluor 750 dye. The obtained results show that the optimized filters represent advanced spectral performance which can be used to improve the sensitivity and the imaging contrast in fluorescence microscopy.
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Determination of microrelief of the sample by singular beams superposition
Статья научная
In present paper we propose easy way to implement method of interfering vortices with opposite topological charge for the real time determination of the thickness and information about the surface of studied samples with the resolution up to 7 nanometers. The determination of the characteristics of the medial cross-section of submicron-objects becomes possible due to phase sensitivity of interfering singular beams to the slightest changes in the optical path difference between them. The dependence of rotational angle of resulting interference pattern in case of different sample thickness for two singular beams superposition is considered in detail.
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