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    Wyświetlanie 1-9 z 9
    Tytuł:
    Compressive optical image encryption using phase-shifting interferometry on a joint transform correlator
    Autorzy:
    Li, J.
    Jia, B.
    Dai, X.
    Lei, M.
    Yang, C.
    Li, H.
    Li, R.
    Powiązania:
    https://bibliotekanauki.pl/articles/174905.pdf
    Data publikacji:
    2017
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    fully optical system
    holographic interferometry
    joint transform correlator (JTC)
    binary scrambling method
    inverse problems
    Opis:
    A compressive optical image encryption method, which combines compressive sensing with phase-shifting interferometry on a joint transform correlator, is proposed in the fully optical domain. The object image is first permutated using a binary scrambling method. Next, the permutated object field is encrypted and registered as the holograms by phase-shifting interferometry on the joint transform correlator setup. Then, the encrypted images and the key are compressed to the compressed data using single-pixel compressive imaging. The original image can be reconstructed and decrypted using the specified algorithm. The simulations demonstrate that the method is effective and suitable for image security transmission.
    Źródło:
    Optica Applicata; 2017, 47, 2; 245-256
    0078-5466
    1899-7015
    Pojawia się w:
    Optica Applicata
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Dual reference beam digital off-axis holography for exact suppression of zero-order term and twin image without spectrum loss
    Autorzy:
    Wang, M.
    Wang, K.
    Zheng, M.
    Li, F.
    Wu, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/174894.pdf
    Data publikacji:
    2017
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    noise suppression
    pixel-by-pixel multiplication
    digital off-axis holography
    Opis:
    In this paper, we describe an effective approach to suppressing zero-order term and twin image by using pixel-by-pixel multiplication of double holograms in digital off-axis holography. This method records two holograms, respectively, by using the reference waves in different directions. It shows not only a simpler algorithm and easier implementation in experiment, but also exact and complete suppression of the zero-order term and twin image without any spectrum loss of the object in the image reconstruction, particularly when the image and the zero-order term are fairly close to each other. The experimental result approves of the theoretical prediction very well. This approach provides an effective solution to suppressing undesired noises in the digital off-axis holography.
    Źródło:
    Optica Applicata; 2017, 47, 3; 435-443
    0078-5466
    1899-7015
    Pojawia się w:
    Optica Applicata
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Improved method for phase wraps reduction in profilometry
    Autorzy:
    Du, G.
    Wang, M.
    Zhou, C.
    Si, S.
    Li, H.
    Lei, Z.
    Li, Y.
    Powiązania:
    https://bibliotekanauki.pl/articles/173793.pdf
    Data publikacji:
    2017
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    phase unwrapping
    zero-padding
    Fourier transform
    carrier-frequency
    profilometry
    Opis:
    In order to completely eliminate, or greatly reduce the number of phase wraps in 2D wrapped phase map, Gdeisat and co-workers proposed an algorithm, which uses shifting the spectrum towards the origin. But the spectrum can be shifted only by an integer number, meaning that the phase wraps reduction is often not optimal. In addition, Gdeisat’s method will take much time to make the Fourier transform, inverse Fourier transform, select and shift the spectral components. In view of the above problems, we proposed an improved method for phase wraps elimination or reduction. First, the wrapped phase map is padded with zeros, the carrier frequency of the projected fringe is determined by high resolution, which can be used as the moving distance of the spectrum. And then realize frequency shift in spatial domain. So it not only can enable the spectrum to be shifted by a rational number when the carrier frequency is not an integer number, but also reduce the execution time. Finally, the experimental results demonstrated that the proposed method is feasible.
    Źródło:
    Optica Applicata; 2017, 47, 2; 295-306
    0078-5466
    1899-7015
    Pojawia się w:
    Optica Applicata
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Dynamic evolution of mixed circular edge-screw dislocations
    Autorzy:
    Gao, P.
    Li, J.
    Cheng, K.
    Duan, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/173359.pdf
    Data publikacji:
    2017
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    mixed circular edge-screw dislocations
    optical vortex
    circular edge dislocations
    atmospheric turbulence
    Opis:
    Based on the extended Huygens–Fresnel principle, the analytical expressions for the cross-spectral density function of mixed circular edge-screw dislocations beams propagating through atmospheric turbulence have been derived, and used to study the dynamic evolution of mixed circular edge-screw dislocations in free space and atmospheric turbulence. It is shown that the radius of circular edge dislocations increases with increasing propagation distance, and both the positions of the optical vortex and the center of circular edge dislocations are located at the point (0, 0) when mixed circular edge-screw dislocations propagate in free space. When mixed circular edge-screw dislocations propagate in the atmospheric turbulence, the position of optical vortices varies with increasing propagation distance, the circular edge dislocation evolves into a pair of optical vortices with the opposite topological charge ±1, and the pair of optical vortices will annihilate as soon as the propagation distance becomes large enough.
    Źródło:
    Optica Applicata; 2017, 47, 3; 471-481
    0078-5466
    1899-7015
    Pojawia się w:
    Optica Applicata
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    One shot profilometry using iterative two-step temporal phase-unwrapping
    Autorzy:
    Du, G.
    Wang, M.
    Zhou, C.
    Si, S.
    Li, H.
    Lei, Z.
    Li, Y.
    Powiązania:
    https://bibliotekanauki.pl/articles/173912.pdf
    Data publikacji:
    2017
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    phase unwrapping
    composite fringe pattern
    Fourier transform
    two-step temporal phase-unwrapping
    Opis:
    This paper reviews two techniques that have been recently published for three-dimensional profilometry and proposes one shot profilometry using iterative two-step temporal phase-unwrapping by combining the composite fringe projection and the iterative two-step temporal phase unwrapping algorithm. In temporal phase unwrapping, many images with different frequency fringe pattern are needed to project, which would take much time. In order to solve this problem, Ochoa proposed a phase unwrapping algorithm based on phase partitions using a composite fringe. However, we found that the fringe order determined through the construction of phase partitions tended to be imprecise. Recently, we proposed an iterative two-step temporal phase unwrapping algorithm, which can achieve high sensitivity and high precision shape measurement. But it needs multiple frames of fringe images which would take much time. In order to take into account both the speed and accuracy of three-dimensional shape measurement, we get a new, and more accurate unwrapping method based on a composite fringe pattern by combining these two techniques. This method not only retains the speed advantage of Ochoa’s algorithm, but also greatly improves its measurement accuracy. Finally, the experimental evaluation is conducted to prove the validity of the proposed method.
    Źródło:
    Optica Applicata; 2017, 47, 1; 97-110
    0078-5466
    1899-7015
    Pojawia się w:
    Optica Applicata
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    3D morphological reconstruction of the red blood cell based on two phase images
    Autorzy:
    Wang, Y
    Li, Z
    Ji, Y
    Xu, Y
    Bu, M
    Powiązania:
    https://bibliotekanauki.pl/articles/174332.pdf
    Data publikacji:
    2015
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    phase imaging
    red blood cell
    3D morphological reconstruction
    maximum entropy
    Opis:
    As an important component of blood cells, the red blood cell plays a vital role in many diseases such as malaria and so on. Although quantitative phase imaging techniques can be used for homogeneous cellular thickness distribution to obtain ideal results, they cannot achieve 3D morphological distribution. In this paper, a new method is presented to get a 3D morphology image of red blood cell. With this method, only two cellular quantitative phase images obtained from two orthogonal directions are needed as original information. By using the grid method, the sample is divided into many small phase cubes, and then we take a layer’s cubes into calculation so that the 3D problem could be transformed into a 2D problem to elaborate. Then it can be applied to the tomographic imaging combined with the maximum entropy method according to the two orthogonal phase images. This method has been proved by a simulation of red blood cell. The results show that cellular morphological distribution can be achieved in detail very well just based on only two orthogonal phase images.
    Źródło:
    Optica Applicata; 2015, 45, 2; 173-182
    0078-5466
    1899-7015
    Pojawia się w:
    Optica Applicata
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Moving-aperture-based three-dimensional micro-measurement system
    Autorzy:
    Fan, S.
    Yu, M.
    Jiang, G.
    Wang, Y.
    Wang, W.
    Li, W.
    Powiązania:
    https://bibliotekanauki.pl/articles/174026.pdf
    Data publikacji:
    2018
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    optical microscopy
    computational photography
    three-dimensional micro-measurement
    moving aperture
    Opis:
    To overcome the depth-of-field limitation of an optical microscope image, a three-dimensional measurement method with a superior depth-of-field is proposed. In the proposed method, light-field information of different angles is obtained by moving the aperture and the three-dimensional scene is reconstructed by using a computational reconstruction technology. First, stereo matching of different aperture position images is performed to obtain the multi-aperture imaging deviation. The focal plane moving distance is thereby estimated. Then, the relational expression between the image coordinates and the focal plane moving distance is determined according to the image coordinates. Two dimensional coordinates of the space point are obtained by the expression coefficients. Finally, the depth coordinates are computed, and three-dimensional reconstruction of the spatial points is completed. Experiments of three-dimensional measurements of the calibration board with different angles and circuit boards are conducted. The results show that the maximum error of the distance measurement is controlled into 0.84%, and the maximum angle measurement error is controlled into 4.56%.
    Źródło:
    Optica Applicata; 2018, 48, 4; 533-547
    0078-5466
    1899-7015
    Pojawia się w:
    Optica Applicata
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Multi-parameter measurement under fiber bending based on directional resonance coupling in photonic crystal fibers
    Autorzy:
    Tan, C.
    Wang, Q.
    Ding, Y.
    Li, H.-W.
    Wang, M.
    Liu, H.
    Powiązania:
    https://bibliotekanauki.pl/articles/174320.pdf
    Data publikacji:
    2018
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    fiber bending
    multi-parameter measurement
    photonic crystal fiber
    fiber sensing
    Opis:
    A multi-parameter sensor with enhanced sensitivity based on magnetic fluids infiltrated photonic crystal fiber is proposed. The sensing performances are investigated using the mode coupling theory and finite element method. Four symmetrical defective channels are assembled into the photonic crystal fiber to produce two resonant transmission dips λCV and λCH in vertical and horizontal directions, respectively. Each dip can be split into two relatively shallow dips (λCV1, λCV2 or λCH1, λCH2) when the photonic crystal fiber is bent. Interestingly, the values of (λCH2 – λCH1) and (λCV2 – λCV1) are associated with corresponding bend-curvature but almost unaffected by external temperature or magnetic field. On the contrary, the values of (λCH2 + λCH1)/2 and (λCV2 + λCV1)/2 are sensitive to temperature or magnetic field regardless of the bending condition. Based on above characteristics and the dependence of the magnetic fluids refractive index on temperature and magnetic field, the proposed sensor can measure not only the bend-curvature and bend-direction, but also the temperature and magnetic field.
    Źródło:
    Optica Applicata; 2018, 48, 3; 449-462
    0078-5466
    1899-7015
    Pojawia się w:
    Optica Applicata
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Polarization properties of Gaussian–Schell model quantization field in a turbulent marine-atmosphere
    Autorzy:
    Zhao, Y.
    Xia, M.
    Wang, Q.
    Li, Y.
    Hu, Z.
    Sun, H.
    Zhang, Y.
    Powiązania:
    https://bibliotekanauki.pl/articles/173639.pdf
    Data publikacji:
    2016
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    polarization fluctuation
    Gaussian–Schell model
    marine-atmosphere
    Kolmogorov turbulence
    Opis:
    Polarization properties of Gaussian–Schell model quantization field propagating through the Kolmogorov turbulence of a marine-atmosphere channel are studied based on the degree of quantum polarization. The effective photon annihilation and creation operators of Gaussian–Schell model quantization field propagation in a marine-atmosphere are developed by making use of the extended Huygens–Fresnel integral of quantum field. The effects of the outer scale on the degree of polarization can be neglected. As the source transverse coherent width, the number of received photons, the inner scale of turbulent eddies, and the source transverse radius decrease or the re- fractive index structure parameter increases, the degree of polarization decreases. In theory, we find that the polarization fade of marine-atmosphere turbulence channels is larger than that of terrene-atmosphere turbulence channels under same transport parameters and the channel with a stronger turbulence strength will possess a larger detection area of a polarization signal, which have potentially important implications for free-space quantum key distribution.
    Źródło:
    Optica Applicata; 2016, 46, 3; 335-345
    0078-5466
    1899-7015
    Pojawia się w:
    Optica Applicata
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-9 z 9

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