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    Wyświetlanie 1-6 z 6
    Tytuł:
    Non-uniform illumination correction based on the retinex theory in digital image correlation measurement method
    Autorzy:
    Gu, G.
    She, B.
    Xu, G.
    Xu, X.
    Powiązania:
    https://bibliotekanauki.pl/articles/173506.pdf
    Data publikacji:
    2017
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    digital image correlation (DIC)
    non-uniform illumination correction
    retinex theory
    deformation measurement
    Opis:
    Digital image correlation is a well-known optical measurement method for full-field deformation and strain measurements. The quality of speckle images used in digital image correlation calculation can directly affect the measurement accuracy of digital image correlation. In most practical measurement circumstances, a uniform illumination environment is usually required to illuminate the detected object in order to capture speckle images upon different deformed states with uniform background intensity. However, the tested object becomes so large that the adopted light source cannot cover all the interested area with uniform illumination, and the speckle images acquired by CCD camera may have non-uniform background intensity distributions. In this paper, the influence of non-uniform illumination is first analyzed in detail by means of a comparison of experimental results of digital image correlation using speckle patterns with both uniform and non-uniform intensity distributions. Then, a new correctional method based on the combination of the basic retinex theory and the illumination formulae of a point light source is proposed. Finally, a real experiment with non-uniform illumination is implemented to verify the effectiveness of this method.
    Źródło:
    Optica Applicata; 2017, 47, 2; 199-208
    0078-5466
    1899-7015
    Pojawia się w:
    Optica Applicata
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Simultaneous measurement of refractive index and thickness for optically transparent object with a dual-wavelength quantitative technique
    Autorzy:
    Xu, X.
    Wang, Y.
    Xu, Y.
    Jin, W.
    Powiązania:
    https://bibliotekanauki.pl/articles/174666.pdf
    Data publikacji:
    2016
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    digital holography
    phase measurement
    cell measurement
    red blood cell
    Opis:
    We present a new dual-wavelength quantitative measurement approach that can be employed for simultaneously measuring both the refractive index and the thickness of the homogenous specimen. This method is realized by dual-wavelength in-line phase-shifting digital holography, and then the phase images are obtained by using four-phase step algorithm for each wavelength separately. Based on computer simulation technology, the feasibility and the effectiveness of our proposed method are demonstrated by comparing our simulation results with the experimental results of the spherical silica bead and the red blood cell, respectively. Our work will provide some guidance in the experimental research for transparent phase objects.
    Źródło:
    Optica Applicata; 2016, 46, 4; 597-605
    0078-5466
    1899-7015
    Pojawia się w:
    Optica Applicata
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Fast near-infrared palmprint recognition using nonnegative matrix factorization extreme learning machine
    Autorzy:
    Xu, X.
    Zhang, X.
    Lu, L.
    Deng, W.
    Zuo, K
    Powiązania:
    https://bibliotekanauki.pl/articles/173572.pdf
    Data publikacji:
    2014
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    extreme learning machine
    palmprint recognition
    superior speed
    support vector machine (SVM)
    Opis:
    Support vector machine and artificial neural network are widely used in classification applications. Extreme learning machine (ELM) is a novel and efficient learning algorithm based on the generalized single hidden layer feed forward networks, which performs well in classification applications. The research results have shown the superiority of ELM with the existing classical algorithms: support vector machine (SVM) and back propagation neural network. In this study, we firstly propose a novel nonnegative matrix factorization extreme learning machine (NMFELM) to improve the performance of standard ELM method. Then we propose a novel near-infrared palmprint recognition approach based on NMFELM classifier. As the test data, we use the near-infrared palmprint database provided by Hong Kong Polytechnic University. The experimental results demonstrate that the proposed NMFELM method outperforms the standard ELM- and SVM-based methods.
    Źródło:
    Optica Applicata; 2014, 44, 2; 285-298
    0078-5466
    1899-7015
    Pojawia się w:
    Optica Applicata
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Abnormal phase removing method in phase measuring profilometry
    Autorzy:
    Xu, X.
    Cao, Y.
    Chen, C.
    Cao, S.
    Peng, K.
    Powiązania:
    https://bibliotekanauki.pl/articles/173504.pdf
    Data publikacji:
    2017
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    information optics
    phase measuring profilometry
    phase shifting algorithm
    phase error
    phase auto-extracting
    Opis:
    An abnormal phase removing method in phase measuring profilometry is proposed. In the five equal shifting phase steps algorithm, the shifting phase might be extracted from the deformed patterns captured by CCD camera. But there may be some errors introduced by a digital fringe projector and CCD camera in these deformed patterns. The impurity of the deformed patterns may lead to four classes of abnormalities when extracting the shifting phase. These abnormalities may cause the wrong shifting phase extraction by which the reconstructed object might be misshapen or anamorphic, or even in failure. By this proposed method, the above abnormalities can be removed, and the shifting phase can be auto-extracted precisely from the impure deformed patterns without knowing its value. Experimental results verify the feasibility and effectiveness of the proposed method.
    Źródło:
    Optica Applicata; 2017, 47, 1; 85-95
    0078-5466
    1899-7015
    Pojawia się w:
    Optica Applicata
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    A method for measuring the quality parameters of image intensifier based on projecting phase-shifting gratings
    Autorzy:
    Sun, S.
    Cao, Y.
    Chen, C.
    Fu, G.
    Wang, Y.
    Xu, X.
    Powiązania:
    https://bibliotekanauki.pl/articles/174300.pdf
    Data publikacji:
    2018
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    phase measurement
    phase-shifting grating
    distortion
    image intensifier
    imaging quality parameter
    Opis:
    A method for measuring the quality parameters of image intensifier based on projecting phase-shifting gratings is proposed. A set of designed phase-shifting gratings are projected into the measuring system orderly to obtain the magnification parameter of the measured image intensifier, and the phase caused by the measured image intensifier. After obtaining the referential phase caused by only the magnification of the measured image intensifier, the phase caused by the distortion of the measured image intensifier is extracted by phase calculating and phase unwrapping. Both the global distortion and the partial distortion of the measured image intensifier can be measured by phase-to-distortion matching at the same time. The experimental results show that the proposed method can measure the multiple quality parameters of image intensifier effectively.
    Źródło:
    Optica Applicata; 2018, 48, 1; 39-51
    0078-5466
    1899-7015
    Pojawia się w:
    Optica Applicata
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Phase features of several typical blood cells and their identification without unwrapping
    Autorzy:
    Wang, Y.
    Chen, Y
    Lü, C.
    Shang, X.
    Xu, Y.
    Wu, H.
    Zhu, X.
    Jin, W.
    Powiązania:
    https://bibliotekanauki.pl/articles/173588.pdf
    Data publikacji:
    2013
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    digital holographic phase
    nucleated cell
    phase model
    wrapped phase features
    identification
    Opis:
    The digital holographic phase microscopy (DHPM) technique which has been proposed for cellular morphology and dynamic analysis yielded highly desirable results. However, for nucleated cells (especially white blood cells (WBCs)), their submicroscopic structure has not yet been deconstructed through a phase unwrapping method due to the heterogeneity of an internal phase. By analyzing the phase heterogeneity of subclasses of WBCs, the typical phase models of them are built first in this paper; using the simulation method, the wrapped phase distributions of these models are obtained. However, by optimizing the wrapped phase maps and analyzing the relationships between them and typical blood cells, their features are selected and extracted. Then the models built are sorted out from each other successfully without unwrapping via analyzing these extracted features, which provides a valuable approach and technological base for the classification and identification of blood cells.
    Źródło:
    Optica Applicata; 2013, 43, 3; 505-514
    0078-5466
    1899-7015
    Pojawia się w:
    Optica Applicata
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-6 z 6

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