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conference on Holography - Advances and Modern Trends Iv

作者： Katkovnik, vladimir Shevkunov, Igor A. Petrov, Nikolay v. Egiazarian, Karen Tampere Univ Technol Dept Signal Proc FIN-33101 Tampere Finland ITMO Univ Dept Photon & Opt Informat Technol St Petersburg 197101 Russia

ISBN: (纸本)9781628416299

The topic of sparse representations (SR) of images has attracted tremendous interest from the research community in the last ten years. This interest stems from the fundamental role that the low dimensional models play in many signal and image processing areas, i.e., real world images can be well approximated by a linear combination of a small number of atoms (i.e., patches of images) taken from a large frame, often termed dictionary. The principal point is that these large dictionaries as well as the elements of these dictionaries taken for approximation are not known in advance and should be taken from given noisy observations. The sparse phase and amplitude reconstruction (SPAR) algorithm has been developed for monochromatic coherent wave field reconstruction, for phase-shifting interferometry and holography. In this paper the SPAR technique is extended to off-axis holography. Pragmatically, SPAR representations are result in design of efficient data-adaptive filters. We develop and study the algorithm where these filters are applied for denoising of phase and amplitude in object and sensor planes. This algorithm is iterative and developed as a maximum likelihood optimal solution provided that the noise in intensity measurements is Gaussian. The multiple simulation and real data experiments demonstrate the advance performance of the new technique.

关键词： digital holography inverse imaging problems off-axis hologram sparsity wavefront reconstruction

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Mining information from atom probe data

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ULTRAMICROSCOPY 2015年第Part2期159卷 324-337页

作者： Cairney, Julie M. Rajan, Krishna Haley, Daniel Gault, Baptiste Bagot, Paula. J. Choi, Pyuck-Pa Felfer, Peter J. Ringer, Simon P. Marceau, Ross K. W. Moody, Michael P. Univ Sydney Sch Aerosp Mech Mechatron Engn Sydney NSW 2006 Australia Univ Sydney Australian Ctr Microscopy & Microanal Sydney NSW 2006 Australia Iowa State Univ Dept Mat Sci & Engn Ames IA 50011 USA Univ Oxford Dept Mat Oxford OX1 3PH England Max Planck Inst Eisenforsch GmbH D-40237 Dusseldorf Germany Deakin Univ Geelong Technol Precinct Inst Frontier Mat Waurn Ponds Vic 3216 Australia

Whilst atom probe tomography (APT) is a powerful technique with the capacity to gather information containing hundreds of millions of atoms from a single specimen, the ability to effectively use this information creates significant challenges. The main technological bottleneck lies in handling the extremely large amounts of data on spatial-chemical correlations, as well as developing new quantitative computational foundations for image reconstruction that target critical and transformative problems in materials science. The power to explore materials at the atomic scale with the extraordinary level of sensitivity of detection offered by atom probe tomography has not been not fully harnessed due to the challenges of dealing with missing, sparse and often noisy data. Hence there is a profound need to couple the analytical tools to deal with the data challenges with the experimental issues associated with this instrument. In this paper we provide a summary of some key issues associated with the challenges, and solutions to extract or "mine" fundamental materials science information from that data. (C) 2015 Published by Elsevier B.v.

关键词： Atom probe tomography Microscopy data mining Clustering Short range order Crystallography

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PhD forum: Hardware-oriented feature extraction based on compressive sensing 9

PhD forum: Hardware-oriented feature extraction based on com...

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9th International conference on Distributed Smart Cameras, ICDSC 2015

作者： Trevisi, Marco Carmona-Galán, Ricardo Rodríguez-vázquez, Ángel Spain

ISBN: (纸本)9781450336819

Feature extraction is used to reduce the amount of resources required to describe a large set of data. A given feature can be represented by a matrix having the same size as the original image but having relevant values only in some specific points. We can consider this sets as being sparse. Under this premise many algorithms have been generated to extract features from compressive samples. None of them though is easily described in hardware. We try to bridge the gap between compressive sensing and hardware design by presenting a sparsifying dictionary that allows compressive sensing reconstruction algorithms to recover features. The idea is to use this work as a starting point to the design of a smart imager capable of compressive feature extraction. To prove this concept we have devised a simulation by using the Harris corner detection and applied a standard reconstruction method, the Nesta algorithm, to retrieve corners instead of a full image. © 2015 ACM.

关键词： Compressed sensing

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image reconstruction in transcranial photoacoustic computed tomography of the brain

Image reconstruction in transcranial photoacoustic computed ...

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conference on Photons Plus Ultrasound - Imaging and Sensing

作者： Mitsuhashi, Kenji Wang, Lihong v. Anastasio, Mark A. Washington Univ Dept Biomed Engn St Louis MO 63130 USA

ISBN: (纸本)9781628414134

Photoacoustic computed tomography (PACT) holds great promise for transcranial brain imaging. However, the strong reflection, scattering, attenuation, and mode-conversion of photoacoustic waves in the skull pose serious challenges to establishing the method. The lack of an appropriate model of solid media in conventional PACT imaging models, which are based on the canonical scalar wave equation, causes a significant model mismatch in the presence of the skull and thus results in deteriorated reconstructed images. The goal of this study was to develop an image reconstruction algorithm that accurately models the skull and thereby ameliorates the quality of reconstructed images. The propagation of photoacoustic waves through the skull was modeled by a viscoelastic stress tensor wave equation, which was subsequently discretized by use of a staggered grid fourth-order finite-difference time-domain (FDTD) method. The matched adjoint of the FDTD-based wave propagation operator was derived for implementing a backprojection operator. Systematic computer simulations were conducted to demonstrate the effectiveness of the backprojection operator for reconstructing images in a realistic three-dimensional PACT brain imaging system. The results suggest that the proposed algorithm can successfully reconstruct images from transcranially-measured pressure data and readily be translated to clinical PACT brain imaging applications.

关键词： Photoacoustic computed tomography image reconstruction Brain imaging

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image registration for limited-view photoacoustic imaging using two linear array transducers

Image registration for limited-view photoacoustic imaging us...

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conference on Photons Plus Ultrasound - Imaging and Sensing

作者： Shu, Weihang Ai, Min Salcudean, Tim Rohling, Robert Abolmaesumi, Purang Tang, Shuo Univ British Columbia Dept Elect & Comp Engn Vancouver BC V6T 1Z4 Canada

ISBN: (纸本)9781628414134

Imaging complicated structures with photoacoustic (PA) modality when the field of view is limited can result in significant imaging artifacts or missing structures. Approaches to solve this problem include new reconstruction algorithms and specific transducer structures, such as hemi-spherical transducer arrays for breast cancer detection. However, most existing PA imaging techniques require either full-view complete projection data collection or complex and computationally-intensive reconstructions. Such approaches are not only time-consuming but also unsuitable for many clinical applications, because most clinical imaging hardware is constrained to limited reconstruction angles. In this paper, we present a method of using two commercial linear array transducers at different orientations to increase the view angle and thus improve the reconstruction of PA imaging. The method involves a two-step process. First, a calibration phantom is imaged to calibrate the relative position of these two linear transducers. Second, two PA images are obtained by a simple back projection algorithm and these images are registered using the information from the calibration process. The final registered image contains more detailed structures without the requirements of a specialized transducer or long processing time. Experimental results show that this method has the potential to provide good image quality using standard low-cost transducers.

关键词： Photoacoustic image registration limited-view

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THE PERFORMANCE EvALUATION OF MULTI-image 3D reconstruction SOFTWARE WITH DIFFERENT SENSORS

THE PERFORMANCE EVALUATION OF MULTI-IMAGE 3D RECONSTRUCTION ...

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International conference on Sensors and Models in Remote Sensing and Photogrammetry

作者： Mousavi, v. Khosravi, M. Ahmadi, M. Noori, N. Naveh, A. Hosseini varshosaz, M. KN Toosi Univ Tecknol Fac Surveying Engeeniring Tehran Iran

ISBN: (纸本)9781629935201

Today, multi-image 3D reconstruction is an active research field and generating three dimensional model of the objects is one the most discussed issues in Photogrammetry and Computer vision that can be accomplished using range-based or image-based methods. very accurate and dense point clouds generated by range-based methods such as structured light systems and laser scanners has introduced them as reliable tools in the industry. image-based 3D digitization methodologies offer the option of reconstructing an object by a set of unordered images that depict it from different viewpoints. As their hardware requirements are narrowed down to a digital camera and a computer system, they compose an attractive 3D digitization approach, consequently, although range-based methods are generally very accurate, image-based methods are low-cost and can be easily used by non-professional users. One of the factors affecting the accuracy of the obtained model in image-based methods is the software and algorithm used to generate three dimensional model. These algorithms are provided in the form of commercial software, open source and web-based services. Another important factor in the accuracy of the obtained model is the type of sensor used. Due to availability of mobile sensors to the public, popularity of professional sensors and the advent of stereo sensors, a comparison of these three sensors plays an effective role in evaluating and finding the optimized method to generate three-dimensional models. Lots of research has been accomplished to identify a suitable software and algorithm to achieve an accurate and complete model, however little attention is paid to the type of sensors used and its effects on the quality of the final model. The purpose of this paper is deliberation and the introduction of an appropriate combination of a sensor and software to provide a complete model with the highest accuracy. To do this, different software, used in previous studies, were compared and

关键词： sensor software image-based 3D reconstruction data comparison point cloud three-dimensional model

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Global Structure-from-Motion by Similarity Averaging 15

Global Structure-from-Motion by Similarity Averaging

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IEEE International conference on Computer vision

作者： Cui, Zhaopeng Tan, Ping Simon Fraser Univ Burnaby BC V5A 1S6 Canada

ISBN: (纸本)9781467383905

Global structure-from-motion (SfM) methods solve all cameras simultaneously from all available relative motions. It has better potential in both reconstruction accuracy and computation efficiency than incremental methods. However, global SfM is challenging, mainly because of two reasons. Firstly, translation averaging is difficult, since an essential matrix only tells the direction of relative translation. Secondly, it is also hard to filter out bad essential matrices due to feature matching failures. We propose to compute a sparse depth image at each camera to solve both problems. Depth images help to upgrade an essential matrix to a similarity transformation, which can determine the scale of relative translation. Thus, camera registration is formulated as a well-posed similarity averaging problem. Depth images also make the filtering of essential matrices simple and effective. In this way, translation averaging can be solved robustly in two convex L-1 optimization problems, which reach the global optimum rapidly. We demonstrate this method in various examples including sequential data, Internet data, and ambiguous data with repetitive scene structures.

关键词： Cameras

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On the design of a sparsifying dictionary for compressive image feature extraction

On the design of a sparsifying dictionary for compressive im...

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IEEE International conference on Electronics, Circuits, and Systems, ICECS 2015

作者： Trevisi, Marco Carmona-Galán, Ricardo Femández-Berni, Jorge Rodríguez-vázquez, Ángel CSIC Universidad de Sevilla Spain

ISBN: (纸本)9781509002467

Compressive sensing is an alternative to Nyquist-rate sampling when the signal to be acquired is known to be sparse or compressible. A sparse signal has a small number of nonzero components compared to its total length. This property can either exist either in the sampling domain, i. e. Time or space, or with respect to a transform basis. There is a parallel between representing a signal in a compressed domain and feature extraction. In both cases, there is an effort to reduce the amount of resources required to describe a large set of data. A given feature is often represented by a set of parameters, which only acquire a relevant value in a few points in the image plane. Although there are some works reported on feature extraction from compressed samples, none of them considers the implementation of the feature extractor as a part of the sensor itself. Our approach is to introduce a sparsifying dictionary, feasibly implementable at the focal plane, which describes the image in terms of features. This allows a standard reconstruction algorithm to directly recover the interesting image features, discarding the irrelevant information. In order to validate the approach, we have integrated a Harris-Stephens corner detector into the compressive sampling process. We have evaluated the accuracy of the reconstructed corners compared to applying the detector to a reconstructed image. © 2015 IEEE.

关键词： Compressed sensing

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3D INTEGRATED METHODOLOGIES FOR THE DOCUMENTATION AND THE vIRTUAL reconstruction OF AN ARCHAEOLOGICAL SITE 6

3D INTEGRATED METHODOLOGIES FOR THE DOCUMENTATION AND THE VI...

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conference on 3D-Arch 2015 - 3D virtual reconstruction and visualization of Complex Architectures

作者： Balletti, C. Guerra, F. Scocca, v. Gottardi, C. Univ Iuav Venezia I-30135 Venice Italy

ISBN: (纸本)9781629935201

Highly accurate documentation and 3D reconstructions are fundamental for analyses and further interpretations in archaeology. In the last years the integrated digital survey (ground-based survey methods and UAv photogrammetry) has confirmed its main role in the documentation and comprehension of excavation contexts, thanks to instrumental and methodological development concerning the on site data acquisition. The specific aim of the project, reported in this paper and realized by the Laboratory of Photogrammetry of the IUAv University of venice, is to check different acquisition systems and their effectiveness test, considering each methodology individually or integrated. This research focuses on the awareness that the integration of different survey's methodologies can as a matter of fact increase the representative efficacy of the final representations;these are based on a wider and verified set of georeferenced metric data. Particularly the methods' integration allows reducing or neutralizing issues related to composite and complex objects' survey, since the most appropriate tools and techniques can be chosen considering the characteristics of each part of an archaeological site (i.e. urban structures, architectural monuments, small findings). This paper describes the experience in several sites of the municipality of Sepino (Molise, Italy), where the 3d digital acquisition of cities and structure of monuments, sometimes hard to reach, was realized using active and passive techniques (rage-based and image based methods). This acquisition was planned in order to obtain not only the basic support for interpretation analysis, but also to achieve models of the actual state of conservation of the site on which some reconstructive hypotheses can be based on. Laser scanning data were merged with Structure from Motion techniques' clouds into the same reference system, given by a topographical and GPS survey. These 3d models are not only the final results of the metric su

关键词： Archaeological Site Documentation Laser Scanning Photogrammetry 3D Modelling 3D reconstruction

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Digital holographic micro-interferometry of nonradiative transitions in biological specimens 2

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conference on Optical Methods for Inspection, Characterization, and Imaging of Biomaterials II

作者： Belashov, A. v. Petrov, N. v. Semenova, I. v. vasyutinskii, O. S. AF Ioffe Phys Tech Inst St Petersburg 194021 Russia ITMO Univ St Petersburg 197101 Russia St Petersburg State Polytech Univ St Petersburg 195251 Russia

ISBN: (纸本)9781628416893

Digital holography is widely used nowadays for interferometric studies of various objects and processes. However, peculiarities of objects under study often imply difficulties in holograms recording, reconstruction and processing. One of the major factors is a typically large number of singular points at phase distributions caused by either low signal to noise ratio at the recorded holograms or sample inhomogeneities. The basic operations applied for absolute phase extracting from digital holograms are noise filtration, phase unwrapping and subtraction of phase distributions. In this paper we demonstrate that the sequence of these operations may drastically affect the resulting image quality and the data obtained. An optimized algorithm suitable for studies of dynamic processes in biological media on microscopic level has been developed. The algorithm was applied for monitoring of nonradiative deactivation processes occurring in onion cell specimens at photosensitized generation of singlet oxygen.

关键词： digital holography digital holographic microscopy holographic interferometry nonradiative relaxation singlet oxygen

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