Search results for "Iterative reconstruction"
showing 10 items of 129 documents
Geometric Properties of the 3D Spine Curve
2003
Through a 3D reconstruction of the human back surface using structured light techniques, we study the properties of spine curve by means of a set of parameters related to measures commonly applied in medicine. In this way, descriptors for measuring the abnormalities in the projections of the front and sagittal planes can be computed. We build the spine curve in 3D and analyse the behaviour of the Frenet frame when along the curve the deformation processes in idiophatic scoliosis appear.
3D reconstruction of transparent objects exploiting surface fluorescence caused by UV irradiation
2010
In this paper, we present a novel approach exploiting fluorescence imaging to estimate the shape of transparent objects. Classical inspection systems require users to coat transparent objects with some powder before measurement. Methods suggested in literature through non contact measurement do not effectively deal with the refraction problem, thus, providing inaccuracies. The proposed method handles the scanning of transparent objects without using any powder and solving the refraction problem using UV environment. A classical triangulation method based on stereovision scheme using fixed stereoscopic visible range cameras with a fixed UV (Ultra Violet) laser source is implemented. Transpar…
Fuzzy Integral Imaging Camera Calibration for Real Scale 3D Reconstructions
2014
In this paper, we present a quantitative analysis of the error in the reconstruction of a 3D scene which has been captured with Synthetic Aperture Integral Imaging system. The 3D information is obtained from 2D images for which the camera parameters are unknown. The model used for calibrating the Integral Imaging camera setup is based on fuzzy systems. These systems provide the opportunity for modeling of conditions which are inherently imprecisely defined. We demonstrate that the error in the 3D reconstruction not only depends on the number of cameras, but also to their relative positions. Our model is applied to a set of images captured experimentally from a real object. A true-color real…
Reducing effects of aberration in 3D fluorescence imaging using wavefront coding with a radially symmetric phase mask.
2016
In this work, a wavefront encoded (WFE) imaging system built using a squared cubic phase mask, designed to reduce the sensitivity of the imaging system to spherical aberration, is investigated. The proposed system allows the use of a space-invariant image restoration algorithm, which uses a single PSF, to restore intensity distribution in images suffering aberration, such as sample–induced aberration in thick tissue. This provides a computational advantage over depth-variant image restoration algorithms developed previously to address this aberration. Simulated PSFs of the proposed system are shown to change up to 25% compared to the 0 µm depth PSF (quantified by the structural similarity i…
Preprocessing of region of interest localization based on local surface curvature analysis for three-dimensional reconstruction with multiresolution
2009
We present an approach to integrate a preprocessing step of the region of interest ROI localization into 3-D scanners laser or ste- reoscopic. The definite objective is to make the 3-D scanner intelligent enough to localize rapidly in the scene, during the preprocessing phase, the regions with high surface curvature, so that precise scanning will be done only in these regions instead of in the whole scene. In this way, the scanning time can be largely reduced, and the results contain only per- tinent data. To test its feasibility and efficiency, we simulated the prepro- cessing process under an active stereoscopic system composed of two cameras and a video projector. The ROI localization is…
Features extraction on complex images
2005
The accessibility of inexpensive and powerful computers has allowed true digital holography to be used for industrial inspection using microscopy. This technique allows the capture of a complex image (i.e., one containing magnitude and phase), and the reconstruction of the phase and magnitude information. Digital holograms give a new dimension to texture analysis, since the topology information can be used as an additional way to extract features. This new technique can be used to extend previous work on the image segmentation of patterned wafers for defect detection. The paper presents a comparison between the features obtained using Gabor filtering on complex images under illumination and…
Extended Depth-of-Field 3-D Display and Visualization by Combination of Amplitude-Modulated Microlenses and Deconvolution Tools
2005
One of the main challenges in 3-D display and visualization is to overcome its limited depth of field. Such limitation is due to the fast deterioration of lateral resolution for out-of-focus object positions. Here we propose a new method to significantly extend the depth of field. The method is based on the combined benefits of a proper amplitude modulation of the microlenses, and the application of deconvolution tools. Numerical tests are presented to verify the theoretical analysis.
Reconstruction Improvement in Integral Fourier Holography by Micro-Scanning Method
2015
Although integral holography has many promising advantages in the field of 3D imaging, the resolution of reconstructed holographic image is still limited by the insufficient information captured. To improve the reconstruction quality, an integral Fourier holographic imaging method based on micro-scanning of the micro-lens array is proposed in this paper. The micro-scanning of the micro-lens array can increase the sampling rate in spatial frequency domain and the information of the generated Fourier hologram, which will eventually eliminate the overlapping effect in the reconstructed 3D image. Experiments for different micro-scanning modes are carried out to verify the feasibility of the pro…
Motion estimation and reconstruction of piecewise planar scenes from two views
2010
The task of recovering the camera motion relative to the environment (motion estimation) is fundamental to many computer vision applications. We present an algorithm for reconstruction of piece-wise planar scenes from only two views and based on minimum line correspondences. We first recover camera rotation by matching vanishing points based on the methods already exist in the literature and then recover the camera translation by searching among a family of hypothesized planes passing through one line. Unlike algorithms based on line segments, the presented algorithm does not require an overlap between two line segments or more than one line correspondence across more than two views to reco…
Phantomuntersuchung zur Optimierung der Spiral-CT und 3 D-Rekonstruktion des Tracheobronchialsystems
1996
PURPOSE To optimise three-dimensional spiral CT of the tracheobronchial tree using adequate acquisition and reconstruction parameters for spiral CT of the chest. MATERIAL AND METHODS Qualitative and quantitative assessment of different 3 D reconstructions of two test objects of the tracheobronchial tree depending on section thickness, reconstruction interval, pitch, and reconstruction algorithm used in spiral CT (Siemens, Somatom plus S) of the chest. The frequency of volume and stairstep artifacts was evaluated. The 3 D reconstructions were generated using a seeded VOI-technique (Allegro, ISG). RESULTS Reduction of artifacts was achieved by decreasing section thickness. Increasing overlap …