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    Wyświetlanie 1-12 z 12
    Tytuł:
    Optical torques and forces in birefringent microplate
    Autorzy:
    Zenkova, C. Y.
    Ivanskyi, D. I.
    Kiyashchuk, T. V.
    Powiązania:
    https://bibliotekanauki.pl/articles/174384.pdf
    Data publikacji:
    2017
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    evanescent wave
    spin angular momentum
    birefringent microplate
    Opis:
    The paper presents a theoretical model for calculating the optical forces caused by the density of spin and orbital momentum and optical torque, caused by the angular momentum typical for a circularly polarized beam or a circular component of an elliptically polarized beam. Total internal reflection at the plate–air interface implemented by the birefringent plate spattered with nanoparticles of gold creates the conditions for the allocation of the predominant action of the vertical spin of the evanescent wave, which has recently been predicted theoretically.
    Źródło:
    Optica Applicata; 2017, 47, 3; 483-493
    0078-5466
    1899-7015
    Pojawia się w:
    Optica Applicata
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Image encryption algorithm by using the logistic map and discrete fractional angular transform
    Autorzy:
    Yu, J.
    Li, Y.
    Xie, X.
    Zhou, N.
    Zhou, Z.
    Powiązania:
    https://bibliotekanauki.pl/articles/173813.pdf
    Data publikacji:
    2017
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    image encryption
    logistic map
    discrete fractional angular transform
    Opis:
    A new image encryption scheme based on logistic map and discrete fractional angular transform has been proposed. In the proposed scheme, the original image is encrypted with the random sequence generated by the logistic map, and the encrypted image is subsequently processed by the discrete fractional angular transform, which produces the ciphertext after double encryptions. The parameters of the logistic map and the order of the discrete fractional angular transform serve as the main keys of the image encryption algorithm. Simulation results show that the proposed image encryption algorithm can effectively resist the attacks of statistical analysis, and has acceptable encryption effect and security.
    Źródło:
    Optica Applicata; 2017, 47, 1; 141-155
    0078-5466
    1899-7015
    Pojawia się w:
    Optica Applicata
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Orbital angular momentum due to modes interference
    Autorzy:
    Rondón Ojeda, Irving
    Soto-Eguibar, Francisco
    Powiązania:
    https://bibliotekanauki.pl/articles/1835754.pdf
    Data publikacji:
    2021
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    invariant beam
    orbital angular momentum
    mode interference
    scalar potential
    Opis:
    We present generalized expressions to calculate the orbital angular momentum for invariant beams using scalars potentials. The solutions can be separated into transversal electric TE, transversal magnetic TM and transversal electromagnetic TE/TM polarization modes. We show that the superposition of non-paraxial vectorial beams with axial symmetry can provide a well-defined orbital angular momentum and that the modes superposition affects the angular momentum flux density. The results are illustrated and analyzed for Bessel beams.
    Źródło:
    Optica Applicata; 2021, 51, 1; 59-74
    0078-5466
    1899-7015
    Pojawia się w:
    Optica Applicata
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Experimental study of an anomalous hollow beam with orbital angular momentum
    Autorzy:
    Lu, Xingyuan
    Zhao, Chengliang
    Hoenders, Bernhard J.
    Yang, Yuanjie
    Cai, Yangjian
    Powiązania:
    https://bibliotekanauki.pl/articles/173518.pdf
    Data publikacji:
    2019
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    anomalous hollow beam
    orbital angular momentum
    focused intensity
    Fourier transform
    Opis:
    Anomalous hollow beam has potential applications in the optical trapping and free space optical communications, etc. It is noted that, thus far, although a large number of studies have been carried out in this field, most of them are theoretical studies and only quite a few cases have experimental results. Here, we experimentally study the generating of anomalous hollow beam carrying orbital angular momentum, and measure its topological charge. We show that the number of dark rings in the Fourier transform of intensity patterns is equal to the topological charge. The experimental results agree well with the simulations.
    Źródło:
    Optica Applicata; 2019, 49, 2; 217-226
    0078-5466
    1899-7015
    Pojawia się w:
    Optica Applicata
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Double-image encryption algorithm based on discrete fractional angular transform and fractional Fourier transform
    Autorzy:
    Qiu, Tian
    Dai, Wei-Hua
    Chen, Su-Hua
    Zhou, Hang
    Gong, Li-Hua
    Powiązania:
    https://bibliotekanauki.pl/articles/2172857.pdf
    Data publikacji:
    2022
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    chaotic system
    fractional transform
    discrete fractional angular transform
    double-image encryption
    Opis:
    By combining fractional Fourier transform with discrete fractional angular transform, a double-image encryption algorithm is designed. The discrete cosine transform is performed on two grayscale images to generate a spectrum image, and then the generated spectrum image is compressed into an image with Zigzag scanning. The compressed image is processed with the discrete fractional angular transform, and then fractional Fourier transform and double random phase coding are executed on the image. The DNA operation controlled by chaotic system is introduced to change the pixel values. Finally, the ciphertext image is obtained through bit-level permutation and pixel adaptive diffusion. The statistical information of the plaintext images is employed as the input of the SHA-256 to calculate the initial conditions of the chaotic map. Simulation experiments demonstrate that the double-image encryption algorithm can effectively reduce the correlation among adjacent pixels of the plaintext images.
    Źródło:
    Optica Applicata; 2022, 52, 4; 669--684
    0078-5466
    1899-7015
    Pojawia się w:
    Optica Applicata
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Image encryption combining discrete fractional angular transform with Arnold transform in image bit planes
    Autorzy:
    Zhou, Z.
    Yu, J.
    Liao, Q.
    Gong, L.
    Powiązania:
    https://bibliotekanauki.pl/articles/173704.pdf
    Data publikacji:
    2018
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    Arnold transform
    bit plane
    discrete fractional angular transform
    image encryption algorithm
    Opis:
    A new image encryption algorithm by using a discrete fractional angular transform and Arnold transform in image bit planes is investigated. In the image encryption algorithm, the original image is encrypted by the Arnold transform in image bit planes firstly, and then the resulting image is encrypted by the discrete fractional angular transform further. The key of the image encryption algorithm includes the parameters of the Arnold transform and the order of the discrete fractional angular transform. It is shown that the proposed image encryption algorithm is of high security and strong enough to counteract some conventional image attack manners.
    Źródło:
    Optica Applicata; 2018, 48, 2; 225-236
    0078-5466
    1899-7015
    Pojawia się w:
    Optica Applicata
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Far and near fields of Hermite–Gaussian beams passing through an annular aperture and its numerical simulation by the angular spectrum method
    Autorzy:
    Talatinian, Alexander
    Powiązania:
    https://bibliotekanauki.pl/articles/27310101.pdf
    Data publikacji:
    2023
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    angular spectrum
    propagation of higher modes
    annular aperture
    near field
    far field
    Opis:
    This research focuses on the analysis of the free propagation of Hermite–Gaussian beams diffracted by a symmetrical annular aperture placed at the beam waist plane. The propagation is studied analytically and numerically using the angular spectrum method and the 2D fast Fourier transformation. Numerical simulation examples illustrate the propagation characteristics of the Hermite–Gaussian beams diffracted by an annular aperture. The beam truncation parameters and obscuration ratio influence Hermite–Gaussian beam diffraction properties.
    Źródło:
    Optica Applicata; 2023, 53, 3; 467--481
    0078-5466
    1899-7015
    Pojawia się w:
    Optica Applicata
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Robust dual color images watermarking scheme with hyperchaotic encryption based on quaternion DFrAT and genetic algorithm
    Autorzy:
    Luo, Hui-Xin
    Gong, Li-Hua
    Chen, Su-Hua
    Powiązania:
    https://bibliotekanauki.pl/articles/27310094.pdf
    Data publikacji:
    2023
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    color image watermarking
    hyperchaotic encryption
    quaternion discrete fractional angular transform
    quaternion singular value decomposition
    genetic algorithm
    Opis:
    A robust dual color images watermarking algorithm is designed based on quaternion discrete fractional angular transform (QDFrAT) and genetic algorithm. To guarantee the watermark security, the original color watermark image is encrypted with a 4D hyperchaotic system. A pure quaternion matrix is acquired by performing the discrete wavelet transform (DWT), the block division and the discrete cosine transform on the original color cover image. The quaternion matrix is operated by the QDFrAT to improve the robustness and the security of the watermarking scheme with the optimal transform angle and the fractional order. Then the singular value matrix is obtained by the quaternion singular value decomposition (QSVD) to further enhance the scheme’s stability. The encryption watermark is also processed by DWT and QSVD. Afterward, the singular value matrix of the encryption watermark is embedded into the singular value matrix of the host image by the optimal scaling factor. Moreover, the values to balance imperceptibility and robustness are optimized with a genetic algorithm. It is shown that the proposed color image watermarking scheme performs well in imperceptibility, security, robustness and embedding capacity.
    Źródło:
    Optica Applicata; 2023, 53, 2; 261--280
    0078-5466
    1899-7015
    Pojawia się w:
    Optica Applicata
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Light field camera all-in-focus image acquisition based on angular information
    Autorzy:
    Wu, Yingchun
    Cheng, Xing
    Liang, Jie
    Wang, Anhong
    Zhao, Xianling
    Powiązania:
    https://bibliotekanauki.pl/articles/1835771.pdf
    Data publikacji:
    2021
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    all-in-focus image fusion
    light field camera
    spatial information
    angular information
    macro-pixel energy difference
    Opis:
    Traditional light field all-in-focus image fusion algorithms are based on the digital refocusing technique. Multi-focused images converted from one single light field image are used to calculate the all-in-focus image and the light field spatial information is used to accomplish the sharpness evaluation. Analyzing the 4D light field from another perspective, an all-in-focus image fusion algorithm based on angular information is presented in this paper. In the proposed method, the 4D light field data are fused directly and a macro-pixel energy difference function based on angular information is established to accomplish the sharpness evaluation. Then the fused 4D data is guided by the dimension increased central sub-aperture image to obtain the refined 4D data. Finally, the all-in-focus image is calculated by integrating the refined 4D light field data. Experimental results show that the fused images calculated by the proposed method have higher visual quality. Quantitative evaluation results also demonstrate the performance of the proposed algorithm. With the light field angular information, the image feature-based index and human perception inspired index of the fused image are improved.
    Źródło:
    Optica Applicata; 2021, 51, 2; 289-304
    0078-5466
    1899-7015
    Pojawia się w:
    Optica Applicata
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Spatial light modulator design and generation of structured electromagnetic waves using digital light processors
    Autorzy:
    Yalcinkaya, F.
    Koc, T.
    Pala, Z.
    Powiązania:
    https://bibliotekanauki.pl/articles/2172826.pdf
    Data publikacji:
    2022
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    spatial light modulator
    digital micro-mirror device
    digital light processing
    structured electromagnetic wave
    orbital angular momentum
    hologram
    Opis:
    Spatial light modulators (SLMs) are versatile devices used for optical studies. These instruments have a wide area of application in photonics. Additionally, SLMs have potential utility in different applications, such as biomedical applications, laser based surgery for precise cutting and as optical tweezers to separate cells in a petri container. However, the high cost of SLM devices prevents their widespread use in many areas, including industrial areas and scientific research laboratories. This paper demonstrates how to design a digital light processor (DLP) based low-cost SLM and describes how to obtain structured electromagnetic waves with the designed SLM. Therefore, this research was undertaken to design and produce a low-cost SLM device for optical applications. For this purpose, two prerequisites had to be fulfilled, the first was to use suitable components of a projection device with DLP-based digital micro-mirror device (DMD), and the second was to eliminate unnecessary SLM components from the system. Finally, holographic images reflected on the SLM screen were created by using Mathematica software program to change the amplitude and phase of the electromagnetic waves in order to obtain the structured electromagnetic waves.
    Źródło:
    Optica Applicata; 2022, 52, 3; 461--479
    0078-5466
    1899-7015
    Pojawia się w:
    Optica Applicata
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Digital watermarking algorithm based on 4-level discrete wavelet transform and discrete fractional angular transform
    Autorzy:
    Li, Jing-You
    Zhao, Chun-Hui
    Zhang, Guang-Da
    Powiązania:
    https://bibliotekanauki.pl/articles/2033921.pdf
    Data publikacji:
    2021
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    digital watermarking algorithm
    mix optical bistability
    Harris feature point detection
    discrete wavelet transform
    discrete fractional angular transform
    singular value decomposition
    Opis:
    Nowadays, there are many watermarking algorithms based on wavelet transform. The simple one is to insert directly the watermark into the wavelet transform coefficients. However, most of the existing watermarking schemes can only resist traditional signal processing attacks, such as image compression, noise and filtering. When the watermarked image is subject to geometric transformations, especially rotation attack, it is hard to detect the watermark successfully. In this paper, a digital watermarking algorithm is proposed based on 4-level discrete wavelet transform and discrete fractional angular transform. To enhance the security of the algorithm, the watermark is scrambled with the simplicity of Arnold transform and chaos-based mix optical bistability model, since the chaos is pseudorandom and sensitive to the initial values. And the watermark is embedded into the medium frequency sub-band of the 1-level wavelet decomposition according to the Harris feature point detection. Simulation results show that the proposed digital watermarking algorithm by combining 4-level discrete wavelet transform with discrete fractional angular transform could resist rotation attack and other common attacks.
    Źródło:
    Optica Applicata; 2021, 51, 4; 605-619
    0078-5466
    1899-7015
    Pojawia się w:
    Optica Applicata
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Evaluation of a high-speed hybrid OAM-OFDM-MDM multiplexed coherent FSO system under desert conditions
    Autorzy:
    Sinha, Shivaji
    Kumar, Chakresh
    Powiązania:
    https://bibliotekanauki.pl/articles/27310107.pdf
    Data publikacji:
    2023
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    atmospheric attenuation
    bit error rate
    BER
    orbital angular momentum
    OAM
    optical signal-to-noise ratio
    OSNR
    orthogonal frequency division multiplexing
    OFDM
    quadrature amplitude modulation
    QAM
    transmission range
    Opis:
    To meet the needs of future wireless optical networks, this paper introduces a high-speed, hybrid multiplexed, coherent free-space optical (FSO) communication system that integrates an orbital angular momentum (OAM) multiplexed signal with an orthogonal frequency division multiplexing (OFDM) technique. Two independent QAM polarized beams, each carrying in-phase and quadrature (I/Q) phase 16-QAM-OFDM modulated data, are combined using mode division multiplexing (MDM) to increase the capacity of the proposed system. The reason of choosing OFDM is its capability to support higher data rate, and mitigating intersymbol interference (ISI). The signal is detected using a coherent detection-based digital signal processing (DSP) algorithm at the receiver end. The proposed hybrid FSO system is evaluated in low and heavy dust environments using bit error rate (BER), link distance, optical signal-to-noise ratio (OSNR), and received optical power performance matrices. The simulation results demonstrate the successful transmission of a 120 Gb/s single carrier over the longest link ranges of 1.5 and 0.40 km, respectively, under low and heavy dust weather environments below the signal degradation threshold value (forward error correction (FEC) limit) of BER 2.2 × 10–3 in strong turbulent conditions.
    Źródło:
    Optica Applicata; 2023, 53, 3; 431--445
    0078-5466
    1899-7015
    Pojawia się w:
    Optica Applicata
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-12 z 12

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