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Applicability Study on Parallax Bundle Adjustment in 3D-Photography
ZUO Zhengkang, YAN Lei, SUN Yanbiao, ZHAO Hongying, ZHANG Ruihua, SUN Jiayu, LIU Siyuan, WANG Qiang, SUN Yiyuan
Acta Scientiarum Naturalium Universitatis Pekinensis    2023, 59 (3): 445-455.   DOI: 10.13209/j.0479-8023.2023.033
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In order to study the applicability of the Parallax Bundle Adjustment (PBA) in the 3D-photography, the authors extend the mathematical proof of the PBA model which is based on the two-dimensional hypothesis, to three dimensions with respect to the sensitivity of parallax angle to observation noise, the singularity of the normal equation, and the degree of linearization. Furthermore, with a set of narrow intersection-angles (2.11×10-8 to 2.11×10-12 rads), the 3D-scenes in short-baseline photography are simulated, and employed to verify the proof. Theoretical analysis and experimental results demenstrate that the current version of PBA is only suitable for the 2D-photography, but not suitable to solve the short-baseline problem in the 3D-photography.
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Microlens-Based Continuous Depth Map Estimation with the Plenoptic Camera
YANG Peng, YAN Lei, ZHAO Shoujiang, YAN Yizhen, ZHAO Hongying
Acta Scientiarum Naturalium Universitatis Pekinensis    2018, 54 (5): 951-960.   DOI: 10.13209/j.0479-8023.2018.053
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Because the micro lenses segment the plenoptic image physically, the global optimization method is hard to be applied on the depth estimation progress and the WTA (winner-take-all) method based on the multibaseline system will generate very coarse but continuous depth map. The global optimizations method always generate robust but concrete depth map when using multi-label technique. So cost projection strategy by directly processing the lenslet plenoptic image is proposed to build the cost volume based on the projection image for global optimization. A method based on Markov Random Fields Propagation (MRFsP) is adopted by merging the modified WTA depth result to refine the concrete depth map. For validation, the depth map built with the proposed method is compared with the microlens-based optimization result, and the result shows obvious improvement.

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Disparity Estimation Method for Free-Texture Scenes Based on Light Field
ZHENG Miao, ZHAO Hongying, YANG Peng, YAN Lei, ZHENG Hongyun, CUI Jialiang
Acta Scientiarum Naturalium Universitatis Pekinensis    2018, 54 (2): 336-340.   DOI: 10.13209/j.0479-8023.2017.116
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In order to improve the pixel distinguishability, this paper introduces an algorithm that the quantized geometric relationship among sub images of light field replaced the pixel value. Based on this relationship, the epipolar line division ratio is calculated to take place of pixel value. Experimental results showed that the disparity map with the division ratio images are obviously superior to those obtained by using the subaperture images.

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Feature Description Method in Dense Matching of UAV Video Images
WEI Yunpeng, ZHAO Hongying, XIN Tiantian, ZHENG Hongyun
Acta Scientiarum Naturalium Universitatis Pekinensis    2016, 52 (6): 990-998.   DOI: 10.13209/j.0479-8023.2016.063
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In order to reduce the time consumption of UAV video image dense matching, and improve processing efficiency, this paper presents a fast feature description and feature matching method. The method uses Harris operator to detect corners, adopts feature descriptor S-DASIY (DASIY) to characterize detected corners and generate the 25-dimensional feature descriptor for the corners. The feature points of the images are matched in accordance with the appropriate matching criteria, to get the match points between images. Experimental results show that the proposed fast feature description and feature matching method can significantly reduce the time of generating and matching feature points.

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