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2010 IEEE/RSJ International conference on Intelligent Robots and Systems

作者： Steven C. Colbert Redwan Alqasemi Rajiv v. Dubey Gregor Franz Konrad Wöllhaf Department of Mechanical Engineering University of South Florida Tampa Florida USA University of Applied Sciences Ravensburg-Weingarten Weingarten Germany

When planning robotic grasping and manipulation maneuvers, knowledge of the shape and pose of the object of interest is critical information. In order for an autonomous or semi-autonomous system to operate intelligently in an unstructured environment and interact with novel objects, it must have the ability to recover this information at run time, even when no a priori information of the object is available. In this paper, we describe the development and testing of an algorithm that can reconstruct the full 3D geometry of a novel object from just three images. A variant of shape from silhouettes, the algorithm first generates a rough surface approximation in the form of a point cloud. This approximation is then refined by fitting an eleven parameter geometric surface to the points in such a manner that the surface ignores noise and perspective projection shadows. We test the algorithm in both simulation and on several real world objects. We show that the algorithm provides accurate reconstructions that can be directly used to plan grasping maneuvers. Compared to other attempts in the literature, the proposed algorithm is faster, requires fewer images, is more accurate, and degrades gracefully in the presence of bad data. A real world test case is included that shows that the algorithm still yields usable results when the form of the object is amorphous or otherwise non-geometric.

关键词： image reconstruction Shape Approximation algorithms Approximation methods Robots Clouds Grasping

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Small-sized computed tomography system with rotating gantry

Small-sized computed tomography system with rotating gantry

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International conference on Electrical Engineering/Electronics, Computer, Telecommunications and Information Technology, ECTI-CON

作者： v. Jantanayingyong T. Chanwimalueang N. Srisuk C. Pintavirooj Faculty of Engineering King Mongkut's Institute of Technology Ladkrabang (KMITL) Thailand

ISBN: (纸本)9781424456062;9789746724913

Small-sized computed tomography system with rotating gantry is presented in this paper. System calibration was performed before achieving the projection data. An object placed on platform was exposed by the x-ray every two degrees of rotating angle. Thus, 180 projection data were performed in this study. Finally, Feldkamp algorithm based on a 3D filtered backprojeciton was employed to reconstruct cross sectional images. The result shows that cross sectional images obtained from small-sized computed tomography were satisfactory. In conclusion, the small-sized computed tomography presented in this study is capable to construct the cross sectional images. Moreover, 3D model reconstructed from these cross sectional images will be performed in the future work.

关键词： Computed tomography X-ray imaging image reconstruction Geometry X-ray detectors X-ray detection Calibration Costs Medical services Biomedical equipment

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Passive imaging of SNM with cosmic-ray generated neutrons and gamma-rays

Passive imaging of SNM with cosmic-ray generated neutrons an...

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IEEE Symposium on Nuclear Science (NSS/MIC)

作者： Konstantin N. Borozdin Christopher Morris Alexei v. Klimenko Randy Spaulding Jeff Bacon Los Alamos National Laboratory Los Alamos NM USA

We present a novel concept of the SNM imaging system based on cosmic-ray muon tracking in coincidence with neutron/gamma detection. The cosmic-ray flux at sea level is about 1 muon/sq. cm/minute. It is composed of nearly equal numbers of μ+ and μ-. In previous work, we have demonstrated that these muons can be used to image nuclear threats in relatively short times by measuring their multiple scattering through objects. Here we propose to image nuclear objects by combining tracking of the muons into a scene with measurements of the secondary particles produced when the muons stop in dense potentially fissile materials. We use multiple drift tube planes to trace incoming cosmic rays. Plastic scintillator serves as a detector of outgoing neutrons and gamma-rays. Additionally, the same plastic scintillator is used to estimate the energy of incoming cosmic-rays. We use a coincidence of n/gamma detection with the initial cosmic-ray trigger to suppress the background. The fissions produced by the stopped μ-generate fission chains that die away after several (~5) fissions. Each fission produces ~10 energetic gamma rays and ~2.5 neutrons. Although a self-shielding needs to be considered, it is likely that tens of neutrons and gamma rays will escape from the object of typical configuration. The efficiency of detecting at least one of the products within ~100 ns could be close to 100% for a detector of reasonably large solid angle (~2 ster). Ten minutes of data should produce 50 trajectories from μ-stopped in 20 kg of U. These numbers can be scaled for other size objects. Our approach has no active source, and therefore it is safe for humans and has no effect on the object under inspection. The detectors are scalable and portable. The drift tubes of the detectors are sealed and do not need the gas replenishment. Detection and localization of SNM is achieved with automatic reconstruction algorithm, which can be run at a standard computer.

关键词： Mesons Neutrons Detectors Gamma rays Cosmic rays Imaging Plastics

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Imaging performance of two multiple-pinhole small-animal SPECT systems: Multiplexed vs. non-multiplexed data acquisition

Imaging performance of two multiple-pinhole small-animal SPE...

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IEEE Symposium on Nuclear Science (NSS/MIC)

作者： Mi-Ae Park Elaine P. Lunsford Robert E. Zimmerman Sudeepti Southekal John v. Frangioni Stephen C. Moore Radiology Department Brigham슠and슠Women''s Hospital and Harvard Medical School Boston MA USA Radiology Department Beth Israel Deaconess Medical Center and Harvard Medical School Boston MA USA

Increasing the number of pinholes in small-animal SPECT significantly improves its count sensitivity. When the detector(s) are small, however, overlapping of projections (multiplexing) from different pinholes is unavoidable and can amplify noise in reconstructed images. We have evaluated the performance of two multi-pinhole systems, one with and one without multiplexing, for a prototypical tumor-imaging task. We prepared seven beads (~1.8-mm diameter) to mimic tumors labeled with Tc-99m. A uniform gelatin phantom was used to simulate normal background tissue. The tumor-to-normal tissue ratio was ~6:1, and each bead contained ~1 μCi. The first scanner, equipped with two 0.8-mm pinholes on each of three heads (HMS-0.8), acquired only non-overlapping projections. We also scanned the phantom using 1.6mm pinholes (HMS-1.6) The second scanner had 9 pinholes on each of four heads, and allowed multiplexing. To compensate for decay, the phantom was scanned for 50 min on HMS-0.8, 58 min on HMS-1.6, 82 min on NanoSPECT/CT with 1.4 mm pinholes (Nano-1.4), and 102 min with 1.0 mm pinholes (Nano-1.0). A total of 30 (24) angular projections were acquired with HMS (Nano); these were reconstructed using 10 OSEM subsets for HMS, and 4 subsets for Nano. The mean voxel value in each sphere, and the mean and standard deviation in a large vOI in the background, were used to compute the signal-to-noise ratio (SNR) and contrast of each bead. The relative noise in the background was also calculated. The systems with and without multiplexing yielded similar image quality and average bead SNR, especially for HMS-0.8 and Nano-1.0. Both systems yielded very similar SNR values, despite the fact that the multiplexed system acquired data using 36 pinholes, while the non-multiplexed system had only 6 pinholes. The multiplexed acquisition did not seem to adversely affect the image contrast of the spherical tumors.

关键词： Multiplexing Imaging image reconstruction Signal to noise ratio Head Animals

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incomplete motion data reconstruction for character animation

Incomplete motion data reconstruction for character animatio...

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IADIS International conference Computer Graphics, visualization, Computer vision and image Processing 2009, CGvCvIP 2009. Part of the IADIS Multi conference on Computer Science and Information Systems, MCCSIS 2009

作者： Xiao, Zhidong Nait-Cherif, Hammadi Zhang, Jian J. National Centre for Computer Animation Media School Bournemouth University United Kingdom

ISBN: (纸本)9789728924843

This paper explores the technique that employs Principal Component Analysis (PCA) for motion synthesis and incomplete motion data reconstruction. A low dimensional space of human motion patterns are generated from a large amount motion capture data using PCA. The generated motion pattern is then applied to synthesize different scaled human character animations with a different speed by interpolation and extrapolation from existing motion patterns. According to animators' desire, we also construct incomplete motion data for a long and continuous motion sequences. This technique provides flexibility for animators to efficiently re-use existing motion capture data for character animation. © 2009 IADIS.

关键词： Motion analysis

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Performance-based assessment of reconstructed images

Performance-based assessment of reconstructed images

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conference on Medical Imaging - image Perception, Observer Performance, and Technology Assessment

作者： Hanson, Kenneth M. Los Alamos Natl Lab Los Alamos NM 87545 USA

ISBN: (纸本)9780819475145

During the early 90s, I engaged in a productive and enjoyable collaboration with Robert Wagner and his colleague, Kyle Myers. We explored the ramifications of the principle that the quality of an image should be assessed on the basis of how well it facilitates the performance of appropriate visual tasks. We applied this principle to algorithms used to reconstruct scenes from incomplete and/or noisy projection data. For binary visual tasks, we used both the conventional disk detection and a new challenging task, inspired by the Rayleigh resolution criterion, of deciding whether an object was a blurred version of two dots or a bar. The results of human and machine observer tests were summarized with the detectability index based on the area under the ROC curve. We investigated a variety of reconstruction algorithms, including ART, with and without a nonnegativity constraint, and the MEMSYS3 algorithm. We concluded that the performance of the Raleigh task was optimized when the strength of the prior was near MEMSYS's default "classic" value for both human and machine observers. A notable result was that the most-often-used metric of rms error in the reconstruction was not necessarily indicative of the value of a reconstructed image for the purpose of performing visual tasks.

关键词： tomographic reconstruction assessment of image quality Rayleigh discrimination task ROC analysis human observer machine observer entropic prior ART reconstruction algorithm MEMSYS Robert Wagner

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Influence of TOF information in OpenPET image reconstruction

Influence of TOF information in OpenPET image reconstruction

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IEEE Nuclear Science Symposium conference 2009

作者： Yamaya, Taiga Yoshida, Eiji Nishikido, Fumihiko Inadama, Naoko Shibuya, Kengo Murayarna, Hideo Natl Inst Radiol Sci Mol Imaging Ctr Chiba Japan Univ Tokyo Grad Sch Arts & Sci Tokyo Japan

ISBN: (纸本)9781424439614

We have proposed an "OpenPET" geometry, which consists of two axially separated detector rings. The central point of the field of view, where the highest sensitivity is obtained, is opened. The OpenPET mainly has three applications, namely, simultaneous PET/CT, extension of the axial FOv, and in-beam PET. In our previous report, we showed that axial spatial resolution, which is degraded with the extended gap due to the parallax error, can be recovered by use of depth-of-interaction (DOI) detectors. On the other hand, image reconstruction of the OpenPET is an incomplete problem because projection data do not satisfy Orlov's condition. Low-frequency components are missing in oblique LORs, i.e., LORs with large ring differences. The gap would suffer from loss of low-frequency components because the gap, where direct LORs (i.e., LORs in the same ring) do not exist, is imaged only from the oblique LORs. In this paper, we focused on time-of-flight (TOF) information, which is expected to compensate for the loss of low-frequency components in the gap. We investigated influence of TOF information in the OpenPET image reconstruction through numerical simulations. Simulated OpenPET scanner had dual detector rings (827.0 mm in diameter and axial length of 153.6 mm each) separated by a gap of 153.6 mm. We supposed that the detectors had a DOI capability of 8 layers and had a TOF capability of 400 ps FWHM resolution. For the non-TOF case, hot-spot objects, which are commonly seen in cancer diagnosis with use of FDG, were imaged without any artifacts, but objects containing more low-frequency components suffered from strong distortion. However, these artifacts were effectively reduced by using TOF information. These results showed that TOF information can compensate for low-frequency components missing in the gap.

关键词： image reconstruction

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Generic and real-time structure from motion using local bundle adjustment

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image AND vISION COMPUTING 2009年第8期27卷 1178-1193页

作者： Mouragnon, E. Lhuillier, M. Dhome, M. Dekeyser, F. Sayd, P. Univ Blaise Pascal CNRS LASMEA UMR 6602 F-63177 Clermont Ferrand France CEA Image & Embedded Comp Lab LIST DTSI SARC F-91191 Gif Sur Yvette France

This paper describes a method for estimating the motion of a calibrated camera and the three-dimensional geometry of the filmed environment. The only data used is video input. Interest points are tracked and matched between frames at video rate. Robust estimates of the camera motion are computed in real-time, key frames are selected to enable 3D reconstruction of the features. We introduce a local bundle adjustment allowing 3D points and camera poses to be refined simultaneously through the sequence. This significantly reduces computational complexity when compared with global bundle adjustment. This method is applied initially to a perspective camera model, then extended to a generic camera model to describe most existing kinds of cameras. Experiments performed using real-world data provide evaluations of the speed and robustness of the method. Results are compared to the ground truth measured with a differential GPS. The generalized method is also evaluated experimentally, using three types of calibrated cameras: stereo rig, perspective and catadioptric. (C) 2008 Elsevier B.v. All rights reserved.

关键词： Structure from motion Bundle adjustment Generic camera

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A topological sampling theorem for Robust boundary reconstruction and image segmentation

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DISCRETE APPLIED MATHEMATICS 2009年第3期157卷 524-541页

作者： Meine, Hans Koethe, Ullrich Stelldinger, Peer Univ Hamburg Cognit Syst Lab D-22527 Hamburg Germany Heidelberg Univ D-69120 Heidelberg Germany

Existing theories on shape digitization impose strong constraints on admissible shapes, and require error-free data. Consequently, these theories are not applicable to most real-world situations. In this paper, we propose a new approach that overcomes many of these limitations. It assumes that segmentation algorithms represent the detected boundary by a set of points whose deviation from the true contours is bounded. Given these error bounds, we reconstruct boundary connectivity by means of Delaunay triangulation and alpha-shapes. We prove that this procedure is guaranteed to result in topologically correct image segmentations under certain realistic conditions. Experiments on real and synthetic images demonstrate the good performance of the new method and confirm the predictions of our theory. (c) 2008 Elsevier B.v. All rights reserved.

关键词： Alpha-shapes Geometric sampling theorem Delaunay triangulation Edgel linking Topology preservation

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Derivative compressive sampling with application to phase unwrapping

Derivative compressive sampling with application to phase un...

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17th European Signal Processing conference, EUSIPCO 2009

作者： Hosseini, Mahdi S. Michailovich, Oleg v. Department of ECE University of Waterloo 200 University Avenue West Waterloo N2L 3G1 ON Canada

reconstruction of multidimensional signals from the samples of their partial derivatives is known to be an important problem in imaging sciences, with its fields of application including optics, interferometry, computer vision, and remote sensing, just to name a few. Due to the nature of the derivative operator, the above reconstruction problem is generally regarded as ill-posed, which suggests the necessity of using some a priori constraints to render its solution unique and stable. The ill-posed nature of the problem, however, becomes much more conspicuous when the set of data derivatives occurs to be incomplete. In this case, a plausible solution to the problem seems to be provided by the theory of compressive sampling, which looks for solutions that fit the measurements on one hand, and have the sparsest possible representation in a predefined basis, on the other hand. One of the most important questions to be addressed in such a case would be of how much incomplete the data is allowed to be for the reconstruction to remain useful. With this question in mind, the present note proposes a way to augment the standard constraints of compressive sampling by additional constraints related to some natural properties of the partial derivatives. It is shown that the resulting scheme of derivative compressive sampling (DCS) is capable of reliably recovering the signals of interest from much fewer data samples as compared to the standard CS. As an example application, the problem of phase unwrapping is discussed. © EURASIP, 2009.

关键词： Compressed sensing

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