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    Wyświetlanie 1-5 z 5
    Tytuł:
    Adaptive lighting for inhomogeneous reflectivity compensation in applications for 3D shape measurements
    Autorzy:
    Casavola, Caterina
    Pappalettera, Giovanni
    Powiązania:
    https://bibliotekanauki.pl/articles/174837.pdf
    Data publikacji:
    2019
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    fringe projection
    structured light projection
    surface reflectivity
    3D contouring
    Opis:
    Surface 3D reconstruction is a topic of great relevance and it has a wide range of applications in many fields such as mechanics, bioengineering and arts. Nowadays optical systems for 3D contouring such as those based on structured light projection are becoming more and more widespread. The possibility to get shape information without any contact with the object, in fact, is a great advantage in some fields such as, for example, cultural heritage. For this class of objects, however, the issue connected with inhomogeneous reflectivity must be taken into account. Due to the different level of reflectivity, in different areas of the object, it comes out that the contrast of the projected pattern changes and, as a direct consequence, the achievable accuracy can change from part to part. In this paper, a study on the possibility to implement an adaptive lighting algorithm is performed allowing to adapt illumination in order to compensate the local inhomogeneities in terms of surface reflectivity.
    Źródło:
    Optica Applicata; 2019, 49, 1; 89-99
    0078-5466
    1899-7015
    Pojawia się w:
    Optica Applicata
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Fringe pattern inpainting based on dual-exposure fused fringe guiding CNN denoiser prior
    Autorzy:
    Peng, Guangze
    Chen, Wenjing
    Powiązania:
    https://bibliotekanauki.pl/articles/2086757.pdf
    Data publikacji:
    2022
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    fringe projection profilometry
    phase calculation
    convolutional neural network
    denoiser prior
    Opis:
    The intensity of some pixels of the captured fringe will be saturated when fringe projection profilometry is used to measure objects with high reflectivity, which will significantly affect the reconstruction of the measured object. In this paper, we propose a fringe pattern inpainting method based on the convolutional neural network (CNN) denoiser prior guided by additional information from a fringe captured in short exposure time. First, a binary mask obtained by Otsu algorithm from the modulation information of the short exposure fringe is used to detect the high-saturation region in the normal exposure fringe. Then, the corrected gray-scales of the region of the short exposure fringe selected by the mask are inserted in the saturated region of the normal fringe to form an initial fringe for iteration. At last, fringe pattern inpainting is achieved by using a CNN denoiser prior. The correct phase can be reconstructed from the inpainted fringes. The computer simulation and experiments verify the effectiveness of the proposed method.
    Źródło:
    Optica Applicata; 2022, 52, 2; 179--193
    0078-5466
    1899-7015
    Pojawia się w:
    Optica Applicata
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Magnified holographic projection based on spatial light modulators
    Autorzy:
    Su, Y.
    Cai, Z.
    Shi, L.
    Zhou, F.
    Chen, H.
    Wu, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/174247.pdf
    Data publikacji:
    2018
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    holographic display
    spatial light modulators
    computer-generated holograms
    magnified holographic projection
    Opis:
    In this paper, a magnified holographic projection based on spatial light modulators is proposed and implemented by combining four magnification methods, including similarity principle of Fourier transform, spatial division, digital lens, and image splicing methods. The Fourier holographic display system is constructed for the experimental verification of the proposed methods. With such four methods of holographic magnification, the reconstruction image can be magnified to 10 × 5 times in two-dimensional directions, which is verified by the experiments. Furthermore, the undesirable light of holographic projection is eliminated by encoding the linear phase onto the computer-generated holograms. The experimental results prove that the proposed system can realize magnified holographic projection with good reconstructed quality, which provides a promising potential for the dynamic holographic projector.
    Źródło:
    Optica Applicata; 2018, 48, 4; 589-600
    0078-5466
    1899-7015
    Pojawia się w:
    Optica Applicata
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Simultaneous intensity projection for projector response computation with application to an active radiometric calibration
    Autorzy:
    Filio-Aguilar, Pedro-David
    López-García, Lourdes
    Rueda-Paz, Juvenal
    Ávila-Aoki, Manuel
    Powiązania:
    https://bibliotekanauki.pl/articles/2172863.pdf
    Data publikacji:
    2022
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    camera-projector compensation
    digital fringe projection
    phase retrieval
    3D imaging
    Opis:
    One of the most important sources of errors in digital fringe projection (DFP) systems is the nonlinearity in the response of the projector when it uses the three-step phase retrieval algorithm. Thus, it is necessary to increase the accuracy without affecting the efficiency. In this sense, the radiometric rectification methods are used. In this paper, an active radiometric rectification method for digital fringe projection is proposed. This proposal consists in two improvements of traditional active techniques: first, parallel intensity projection is used to obtain the projector response which requires only four dot patterns; and second, a method is provided for the calculation of the inverse polynomial that guarantees symmetry with respect to the response of the projector. Experimental results, in a digital fringe projection system, show that the root-mean-square phase error improves 6.3 times using this proposal.
    Źródło:
    Optica Applicata; 2022, 52, 4; 521--533
    0078-5466
    1899-7015
    Pojawia się w:
    Optica Applicata
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Neural network model for phase-height relationship of each image pixel in 3D shape measurement by machine vision
    Autorzy:
    Chung, B
    Powiązania:
    https://bibliotekanauki.pl/articles/173298.pdf
    Data publikacji:
    2014
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    machine vision
    shape measurement
    fringe pattern projection
    phase-height relationship
    neural network
    Opis:
    In a three-dimensional measurement system based on a digital light processing projector and a camera, a height estimating function is very important. Sinusoidal fringe patterns of the projector are projected onto the object, and the phase of the measuring point is calculated from the camera image. Then, the height of the measuring point is inferred by the phase. The phase-to-height relationship is unique at each image point. However it is nonlinearly different according to the image coordinates. It is also difficult to obtain the geometrical model because of lens distortion. Even though some studies have been performed on neural network models to find the height from the phase and the related coordinates, the results are not good because of the complex relationship. Therefore, this paper proposes a hybrid method that combines a geometric analysis and a neural network model. The proposed method first finds the phase-to-height relationship from a geometric analysis for each image pixel, and then uses a neural network model to find the related parameters for the relationship. The experimental results show that the proposed method is superior to previous neural network methods.
    Źródło:
    Optica Applicata; 2014, 44, 4; 587-599
    0078-5466
    1899-7015
    Pojawia się w:
    Optica Applicata
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-5 z 5

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