3D Reconstruction of Underwater Natural Scenes and Objects Using Stereo Vision

Over the last two decades, research community of computer vision has developed various techniques suitable for underwater applications using intensity images. This chapter will explore 3D reconstruction of underwater natural scenes and objects based on stereo vision, which will be helpful in mine detection, inspection of shipwrecks, detection of telecommunication cables and pipelines. The general steps involved in 3D reconstruction using stereo vision are provided. The brief summary of papers for 3D reconstruction of underwater environment is presented. 3D reconstruction of underwater natural scenes and objects is challenging problem due to light propagation in underwater. In contrast to light propagation in the air, the light rays are attenuated and scattered, having a great effect on image quality. We have proposed preprocessing technique to enhance degraded underwater images. At the end of the chapter, we have presented the proposed stereo vision based 3D reconstruction technique to reconstruct 3D surface of underwater objects. Ultimately, this chapter intends to give an overview of the 3D reconstruction technique using stereo vision in order to help a reader in understanding stereo vision and its benefits for underwater applications.

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A novel cooling hole inspection method for turbine blade using 3D reconstruction of stereo vision

Measurement Science and Technology ◽

10.1088/1361-6501/ac39d0 ◽

2021 ◽

Author(s):

Yuqi Cheng ◽

Wenlong Li ◽

Cheng Jiang ◽

Gang Wang ◽

Wei Xu ◽

...

Keyword(s):

3D Reconstruction ◽

Turbine Blade ◽

Stereo Vision ◽

Heat Dissipation ◽

Turbine Blades ◽

Reconstruction Technique ◽

Feature Points ◽

Inspection Method ◽

Reconstruction Methods ◽

Cooling Hole

Abstract Cooling holes (number 100~200, diameter 0.3~1.2 mm) are important heat dissipation structures of a turbine blade in aero-engine. Due to the small sizes and similar contours of cooling holes, it is difficult to extract and match their features by traditional stereo reconstruction methods. This paper proposes a novel cooling hole inspection method for turbine blades utilizing 3D reconstruction technique of stereo vision, which combines the stereo vision principle with the invariance of cross-ratio. The feature points of contours are extracted and matched by calculating two intersection points of circular contours and a line through the center points of adjacent cooling holes. Additionally, the 3D points corresponding to the feature points are reconstructed, by which, the diameters of cooling holes can be calculated successfully. Moreover, measurement experiments verify the effectiveness and accuracy of the proposed method. The experimental results show that the average errors of the standard circle ruler and tiny hole sample are within 0.05 mm, which satisfies the inspection requirement of cooling holes.

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3D Reconstruction with Single-Shot Structured Light RGB Line Pattern

Sensors ◽

10.3390/s21144819 ◽

2021 ◽

Vol 21 (14) ◽

pp. 4819

Author(s):

Yikang Li ◽

Zhenzhou Wang

Keyword(s):

3D Reconstruction ◽

Moving Objects ◽

Structured Light ◽

Color Space ◽

Reconstruction Technique ◽

Single Shot ◽

Line Pattern ◽

Hsv Color Space ◽

Phase Map ◽

Line Segmentation

Single-shot 3D reconstruction technique is very important for measuring moving and deforming objects. After many decades of study, a great number of interesting single-shot techniques have been proposed, yet the problem remains open. In this paper, a new approach is proposed to reconstruct deforming and moving objects with the structured light RGB line pattern. The structured light RGB line pattern is coded using parallel red, green, and blue lines with equal intervals to facilitate line segmentation and line indexing. A slope difference distribution (SDD)-based image segmentation method is proposed to segment the lines robustly in the HSV color space. A method of exclusion is proposed to index the red lines, the green lines, and the blue lines respectively and robustly. The indexed lines in different colors are fused to obtain a phase map for 3D depth calculation. The quantitative accuracies of measuring a calibration grid and a ball achieved by the proposed approach are 0.46 and 0.24 mm, respectively, which are significantly lower than those achieved by the compared state-of-the-art single-shot techniques.

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3D reconstruction accuracy improvement of the stereo vision system by changing the convergence angle of cameras

Оптический журнал ◽

10.17586/1023-5086-2021-88-10-33-38 ◽

2021 ◽

Keyword(s):

3D Reconstruction ◽

Stereo Vision ◽

Vision System ◽

Reconstruction Accuracy ◽

Accuracy Improvement ◽

Convergence Angle ◽

Stereo Vision System

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Light propagation and optical scalars in torsion theories of gravity

Modern Physics Letters A ◽

10.1142/s0217732319500299 ◽

2019 ◽

Vol 34 (04) ◽

pp. 1950029

Author(s):

Siamak Akhshabi

Keyword(s):

Gravitational Lensing ◽

Light Propagation ◽

Raychaudhuri Equation ◽

Angular Diameter Distance ◽

Propagation Of Light ◽

Light Rays ◽

Theories Of Gravity ◽

Torsion Theories ◽

Basic Equations ◽

Gauge Theory Of Gravity

We investigate the propagation of light rays and evolution of optical scalars in gauge theories of gravity where torsion is present. Recently, the modified Raychaudhuri equation in the presence of torsion has been derived. We use this result to derive the basic equations of geometric optics for several different interesting solutions of the Poincaré gauge theory of gravity. The results show that the focusing effects for neighboring light rays will be different than general relativity. This in turn has practical consequences in the study of gravitational lensing effects and also in determining the angular diameter distance for cosmological objects.

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Linear Correction and Matching Method for 3D Line Structure Reconstruction

Mathematical Problems in Engineering ◽

10.1155/2020/3597397 ◽

2020 ◽

Vol 2020 ◽

pp. 1-11

Author(s):

Di Jia ◽

Yuxiu Li ◽

Si Wu ◽

Ying Liu

Keyword(s):

3D Reconstruction ◽

Large Scale ◽

Computational Cost ◽

Small Neighborhood ◽

Line Detection ◽

Reconstruction Technique ◽

Matching Method ◽

Line Structure ◽

Straight Line ◽

Linear Correction

The 3D reconstruction technique using the straight-line segments as features has high precision and low computational cost. The method is especially suitable for large-scale urban datasets. However, the line matching step in the existing method has a mismatching problem. The two main reasons for this problem are the line detection result is not located at the true edge of the image and there is no consistency check of the matching pair. In order to solve this problem, a linear correction and matching method for 3D reconstruction of target line structure is proposed in this paper. Firstly, the edge features of the image are extracted to obtain a binarized edge map. Then, the extended gradient map is calculated using the edge map and the gradient to establish the gradient gravitational map. Secondly, the straight-line detection method is used to extract all the linear features used for the 3D reconstruction image, and the linear position is corrected by the gradient gravitational map. Finally, the point feature matching result is used to calculate the polar line, and the line matching results of the adjacent three images are used to determine the final partial check feature area. Then, random sampling is used to obtain the feature similarity check line matching result in the small neighborhood. The aforementioned steps can eliminate the mismatched lines. The experimental results demonstrate that the 3D model obtained using the proposed method has higher integrity and accuracy than the existing methods.

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A genesis of special relativity

International Journal of Modern Physics D ◽

10.1142/s0218271815300244 ◽

2015 ◽

Vol 24 (10) ◽

pp. 1530024

Author(s):

Valérie Messager ◽

Christophe Letellier

Keyword(s):

Special Relativity ◽

19Th Century ◽

Maxwell Equations ◽

Light Propagation ◽

Principle Of Relativity ◽

Light Rays ◽

Optical Phenomena ◽

Light Particles ◽

The 19Th Century ◽

The Waves

The genesis of special relativity is intimately related to the development of the theory of light propagation. When optical phenomena were described, there are typically two kinds of theories: (i) One based on light rays and light particles and (ii) one considering the light as waves. When diffraction and refraction were experimentally discovered, light propagation became more often described in terms of waves. Nevertheless, when attempts were made to explain how light was propagated, it was nearly always in terms of a corpuscular theory combined with an ether, a subtle medium supporting the waves. Consequently, most of the theories from Newton's to those developed in the 19th century were dual and required the existence of an ether. We therefore used the ether as our Ariadne thread for explaining how the principle of relativity became generalized to the so-called Maxwell equations around the 1900's. Our aim is more to describe how the successive ideas were developed and interconnected than framing the context in which these ideas arose.

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