scholarly journals Three-Dimensional Reconstruction of Mechanical Parts Based on Digital Holography

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Yaohui Dai ◽  
Haiyu Wu ◽  
Gang Zhu ◽  
Yan Yang
Keyword(s):  
Digital Holography ◽  
Optimization Problems ◽  
Three Dimensional ◽  
3D Display ◽  
Mechanical Parts ◽  
First Order ◽  
Reconstruction Image ◽  
Dimensional Reconstruction ◽  
Order Image

In reconstruction of the off-axis digital hologram of diffuse reflection objects, the position of the positive first-order image cannot be accurately obtained because of the low quality of the reconstruction image. This paper focuses on the above problem and proposes a method for marking the first-order image of the 1-FFT surface based on the fast Fourier transform (1-FFT). The parameters of angle of illumination light were investigated, and the maximum relative measurement error is 5.6% by standard objects. The multiaperture stitching technique in cylindrical coordinates is applied to digital holography technology, and the particle swarm optimization algorithm is used to transform the nonlinear equations into optimization problems to solve the splicing parameters. Finally, the 3D display of a typical rotary three-dimensional mechanical part is successfully realized with holography stitching using the above method.

Semi-automated methods for 3-D reconstruction of macromolecular complexes

1995 ◽  
Vol 53 ◽  
pp. 42-43
Author(s):  
B. Carragher ◽  
M. Whittaker
Keyword(s):  
Three Dimensional ◽  
Time Saving ◽  
Macromolecular Complexes ◽  
Symmetry Properties ◽  
Dimensional Reconstruction ◽  
Experienced Operator ◽  
Projection Images ◽  
The Individual ◽  
Natural Symmetry

Techniques for three-dimensional reconstruction of macromolecular complexes from electron micrographs have been successfully used for many years. These include methods which take advantage of the natural symmetry properties of the structure (for example helical or icosahedral) as well as those that use single axis or other tilting geometries to reconstruct from a set of projection images. These techniques have traditionally relied on a very experienced operator to manually perform the often numerous and time consuming steps required to obtain the final reconstruction. While the guidance and oversight of an experienced and critical operator will always be an essential component of these techniques, recent advances in computer technology, microprocessor controlled microscopes and the availability of high quality CCD cameras have provided the means to automate many of the individual steps.During the acquisition of data automation provides benefits not only in terms of convenience and time saving but also in circumstances where manual procedures limit the quality of the final reconstruction.

Effect of Dissipative Terms on the Quality of Two and Three-Dimensional Euler Flow Solutions

2008 ◽  
Author(s):  
Seyed Saied Bahrainian
Keyword(s):  
Euler Equations ◽  
Hyperbolic Conservation Laws ◽  
Three Dimensional ◽  
Strong Shock ◽  
Computational Domain ◽  
Third Order ◽  
First Order ◽  
Proper Values ◽  
Dissipative Terms

The Euler equations are a set of non-dissipative hyperbolic conservation laws that can become unstable near regions of severe pressure variation. To prevent oscillations near shockwaves, these equations require artificial dissipation terms to be added to the discretized equations. A combination of first-order and third-order dissipative terms control the stability of the flow solutions. The assigned magnitude of these dissipative terms can have a direct effect on the quality of the flow solution. To examine these effects, subsonic and transonic solutions of the Euler equations for a flow passed a circular cylinder has been investigated. Triangular and tetrahedral unstructured grids were employed to discretize the computational domain. Unsteady Euler equations are then marched through time to reach a steady solution using a modified Runge-Kutta scheme. Optimal values of the dissipative terms were investigated for several flow conditions. For example, at a free stream Mach number of 0.45 strong shock waves were captured on the cylinder by using values of 0.25 and 0.0039 for the first-order and third-order dissipative terms. In addition to the shock capturing effect, it has been shown that smooth pressure coefficients can be obtained with the proper values for the dissipative terms.

A modified discrete tomography for improving the reconstruction of unknown multi-gray-level material in the `missing wedge' situation

2018 ◽  
Vol 25 (6) ◽  
pp. 1847-1859 ◽  
Author(s):  
Jianhong Liu ◽  
Zhiting Liang ◽  
Yong Guan ◽  
Wenbin Wei ◽  
Haobo Bai ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Iteration Process ◽  
Reconstruction Technique ◽  
Morphological Operations ◽  
Algebraic Reconstruction Technique ◽  
Discrete Tomography ◽  
Boundary Extraction ◽  
X Ray ◽  
Dimensional Reconstruction

Full angular rotational projections cannot always be acquired in tomographic reconstructions because of the limited space in the experimental setup, leading to the `missing wedge' situation. In this paper, a recovering `missing wedge' discrete algebraic reconstruction technique algorithm (rmwDART) has been proposed to solve the `missing wedge' problem and improve the quality of the three-dimensional reconstruction without prior knowledge of the material component's number or the material's values. By using oversegmentation, boundary extraction and mathematical morphological operations, `missing wedge' artifact areas can be located. Then, in the iteration process, by updating the located areas and regions, high-quality reconstructions can be obtained from the simulations, and the reconstructed images based on the rmwDART algorithm can be obtained from soft X-ray nano-computed tomography experiments. The results showed that there is the potential for discrete tomography.

scholarly journals Simulation of Multi-Camera Indoor and Outdoor 3D Scanner

2018 ◽  
Vol 2 (3) ◽  
pp. 33-41
Author(s):  
Keyword(s):  
Three Dimensional ◽  
System Structure ◽  
3D Scanner ◽  
Background Removal ◽  
Dimensional Reconstruction ◽  
Characteristic Points ◽  
Graphic Engine ◽  
The Impact ◽  
Indoor And Outdoor

Photogrammetry allows a three-dimensional reconstruction of the object based on its multiple photography’s. The quality of the reconstruction result depends mostly on the gloss, the diversity of the texture, the lighting conditions, the quality of the camera calibration and the shape of the object. The article presents the results of a simulation of a multi-camera reconstruction system, for the needs of designing indoor and outdoor 3D scanner. The 3D reconstruction system works by simultaneously taking photographs of cameras located around the object. The simulation was created to investigate the optimal distribution of cameras and projectors casting a pattern that increases the number of characteristic points on the surface of the object. The impact of background removal in images on the reconstruction result as well as the texture quality of the object depending on the resolution and distance of the cameras from the object were also investigated. The graphic engine used to create the simulation also allows testing of impact of various conditions. The presented results prove that the parameters of the system structure, such as the placement of cameras, projectors, the selection of patterns projected by the projectors are important and their values can be determined at the stage of system simulation. The acquired results are promising and will be further investigated.

scholarly journals Wavelength-Selective Phase-Shifting Digital Holography: Color Three-Dimensional Imaging Ability in Relation to Bit Depth of Wavelength-Multiplexed Holograms

2018 ◽  
Vol 8 (12) ◽  
pp. 2410 ◽  
Author(s):  
Tatsuki Tahara ◽  
Reo Otani ◽  
Yasuhiro Takaki
Keyword(s):  
Digital Holography ◽  
3D Imaging ◽  
Dynamic Range ◽  
Three Dimensional ◽  
Image Sensor ◽  
Phase Shifting ◽  
3D Images ◽  
Wavelength Resolution ◽  
The Relationship

The quality of reconstructed images in relation to the bit depth of holograms formed by wavelength-selective phase-shifting digital holography was investigated. Wavelength-selective phase-shifting digital holography is a technique to obtain multiwavelength three-dimensional (3D) images with a full space-bandwidth product of an image sensor from wavelength-multiplexed phase-shifted holograms and has been proposed since 2013. The bit resolution required to obtain a multiwavelength holographic image was quantitatively and experimentally evaluated, and the relationship between wavelength resolution and dynamic range of an image sensor was numerically simulated. The results indicate that two-bit resolution per wavelength is required to conduct color 3D imaging.

scholarly journals RESEARCH ON THE FACTORS AFFECTING THE ACCURACY OF THREE-DIMENSIONAL RECONSTRUCTION MODEL OF ROTOR UAV ARCHAEOLOGICAL SITES

2019 ◽  
Vol XLII-4/W20 ◽  
pp. 111-118
Author(s):  
X. Zheng ◽  
Y. G. Hu
Keyword(s):  
New Technologies ◽  
Three Dimensional ◽  
Archaeological Sites ◽  
Three Dimensional Reconstruction ◽  
Factors Affecting ◽  
Dimensional Reconstruction ◽  
Archaeological Work ◽  
Heritage Protection ◽  
Cultural Relics

Abstract. The work of cultural heritage protection has risen to the national strategic level in China in recent years. More and more high and new technologies are applied in the fields of cultural relics and archaeology, heritage protection, etc., including the drone photography technology. Because the cultural protection industry has high requirements for the accuracy of reconstruction results, it puts forward higher requirements for the three-dimensional reconstruction of drones. In this paper, the factors affecting the reconstruction accuracy of the rotor unmanned opportunity are analyzed and summarized in the archaeological protection of cultural relics, and the technical integration of the oblique photography technology in archaeological work is carried out to improve the quality of modeling results.

A Fast and Smooth Carving Algorithm for Online 3D Reconstruction

2013 ◽  
Vol 311 ◽  
pp. 153-157
Author(s):  
Xing Gao ◽  
Ning Yu ◽  
Ming Hong Liao
Keyword(s):  
3D Reconstruction ◽  
Three Dimensional ◽  
Three Dimensional Reconstruction ◽  
Heritage Preservation ◽  
Reconstruction Methods ◽  
Space Carving ◽  
Dimensional Reconstruction ◽  
Bio Engineering ◽  
Current Reconstruction

Online rapid three-dimensional reconstruction is widely applied in virtual reality, heritage preservation, bio-engineering and architectural fields. The error caused by image quality or manual import is the main reason for the low quality of model details when applying current reconstruction methods while meeting the time premise. To solve this problem, the paper proposes a fast and smooth carving algorithm for online 3d reconstruction by joining the filter. By applying the method, you can get a more realistic and smooth three-dimensional reconstruction results. First, we convert the input point cloud to meshes through Delaunay tetrahedralisation. Then we reconstruct the model with the space carving algorithm with the filter to obtain the result. The experiment result shows our method exceeds existing methods while meeting the time constraints under the premise at the same time.

scholarly journals Evaluation of the effect of filters on reconstructed image quality from cone beam CT system

2021 ◽  
Vol 11 (1) ◽  
pp. 35-47
Author(s):  
Ngoc Ha Bui ◽  
Tien Hung Bui ◽  
Thuy Duong Tran ◽  
Kim Tuan Tran ◽  
Ngoc Toan Tran
Keyword(s):  
Image Quality ◽  
Cone Beam Ct ◽  
Three Dimensional ◽  
Reconstruction Algorithm ◽  
Reconstructed Image ◽  
Cone Beam ◽  
Spatial Filters ◽  
Dimensional Reconstruction ◽  
Ct System

: 3D Filtered Back Projection (FBP) is a three-dimensional reconstruction algorithm usually used in Cone Beam Computed Tomography (CBCT) system. FBP is one of the most popular algorithms due to its reconstruction is fast while quality of the result is acceptable. It can also handle a more considerable amount of data with same computer performance with other algorithms. However, the quality of a reconstructed image by the FBP algorithm strongly depends on spatial filters and denoising filters applied to projections. In this paper an evaluation of the reconstructed image quality of the CBCT system by using different denoising filters and spatial filters to find out the best filters for the CBCT system is performed. The result shows that, there is a significantly decrease of the noise of projection with the combination of Median and Gaussian filters. The reconstructed image has high resolution with Cosine filter and becomes more sharpen with Hanning filter.

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