Language：English   Publishing type：Research paper (international conference proceedings)

Online   Online   2022.02.06  -  2022.02.08

When light passes through a liquid, its energy is attenuated due to absorption. The attenuation depends both on the spectral absorption coefficient of a liquid and on the optical path length of light, and is described by the Lambert-Beer law. The spectral absorption coefficients of liquids are often unknown in real-world applications and to be measured/estimated in advance, because they depend not only on liquid media themselves but also on dissolved materials. In this paper, we propose a method for estimating the spectral absorption coefficient of a liquid only from two-view hyperspectral images of an under-liquid scene taken from the outside of the liquid in a passive and non-contact manner. Specifically, we show that the estimation results in Non-negative Matrix Factorization (NMF) because both the objective variables and the explanatory variables are all nonnegative, and then study the ambiguity in matrix factorization. We conducted a number of experiments using real hyperspectral images, and confirmed that our method works well and is useful for reconstructing shape of an under-liquid scene.

DOI： 10.5220/0010917600003124

DOI： 10.5220/0010917600003124

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Language：English   Publishing type：Research paper (scientific journal)

In this paper, we introduce a novel method for reconstructing surface normals and depth of dynamic objects in water. Past shape recovery methods have leveraged various visual cues for estimating shape (e.g., depth) or surface normals. Methods that estimate both compute one from the other. We show that these two geometric surface properties can be simultaneously recovered for each pixel when the object is observed underwater. Our key idea is to leverage multi-wavelength near-infrared light absorption along different underwater light paths in conjunction with surface shading. Our method can handle both Lambertian and non-Lambertian surfaces. We derive a principled theory for this surface normals and shape from water method and a practical calibration method for determining its imaging parameters values. By construction, the method can be implemented as a one-shot imaging system. We prototype both an off-line and a video-rate imaging system and demonstrate the effectiveness of the method on a number of real-world static and dynamic objects. The results show that the method can recover intricate surface features that are otherwise inaccessible.

DOI： 10.1109/TPAMI.2021.3121963

Scopus

PubMed

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)

We introduce a novel 3D sensing method for recovering a consistent, dense 3D shape of a dynamic, non-rigid object in water. The method reconstructs a complete (or fuller) 3D surface of the target object in a canonical frame (e.g., rest shape) as it freely deforms and moves between frames by estimating underwater 3D scene flow and using it to integrate per-frame depth estimates recovered from two near-infrared observations. The reconstructed shape is refined in the course of this global non-rigid shape recovery by leveraging both geometric and radiometric constraints. We implement our method with a single camera and a light source without the orthographic assumption on either by deriving a practical calibration method that estimates the point source position with respect to the camera. Our reconstruction method also accounts for scattering by water. We prototype a video-rate imaging system and show 3D shape reconstruction results on a number of real-world static, deformable, and dynamic objects and creatures in real-world water. The results demonstrate the effectiveness of the method in recovering complete shapes of complex, non-rigid objects in water, which opens new avenues of application for underwater 3D sensing in the sub-meter range.

DOI： 10.1109/TPAMI.2021.3075450

Scopus

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)

DOI： 10.1109/CVPR46437.2021.01459

Scopus

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)

DOI： 10.1109/CVPR46437.2021.00074

Scopus

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Authorship：Lead author   Language：English   Publishing type：Research paper (international conference proceedings)

DOI： 10.1109/WACV45572.2020.9093268

Scopus

Other Link： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85085485176&origin=inward

Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)

In this paper, we introduce a novel method for reconstructing surface normals and depth of dynamic objects in water. Past shape recovery methods have leveraged various visual cues for estimating shape (e.g., depth) or surface normals. Methods that estimate both compute one from the other. We show that these two geometric surface properties can be simultaneously recovered for each pixel when the object is observed underwater. Our key idea is to leverage multi-wavelength near-infrared light absorption along different underwater light paths in conjunction with surface shading. We derive a principled theory for this surface normals and shape from water method and a practical calibration method for determining its imaging parameters values. By construction, the method can be implemented as a one-shot imaging system. We prototype both an off-line and a video-rate imaging system and demonstrate the effectiveness of the method on a number of real-world static and dynamic objects. The results show that the method can recover intricate surface features that are otherwise inaccessible.

DOI： 10.1109/ICCV.2019.00792

Scopus

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)

DOI： 10.1016/j.mio.2016.08.002

Scopus

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)

This paper is aimed at proposing a new structured light pattern for mirror-based multi-view active stereo so that the patterns cast onto the object surface do not interfere even where the object is illuminated by the projector directly and indirectly via mirror. The key idea of our interference-free projection is to encode the projector pixel locations so that they do not collide with the code from other projector pixels by exploiting the epipolar geometry defined by the real and the virtual projectors. We prove that our new encoding does not generate code collisions between the direct and indirect patterns from the real and the virtual projectors respectively. Evaluations using real and synthesized datasets demonstrate that our approach can realize an interference-free projection without using specialized equipment such as orthographic projectors used in the state-of-the-art methods.

DOI： 10.1109/3DV.2015.25

Scopus

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