6,315 research outputs found
3D Reconstruction with Low Resolution, Small Baseline and High Radial Distortion Stereo Images
In this paper we analyze and compare approaches for 3D reconstruction from
low-resolution (250x250), high radial distortion stereo images, which are
acquired with small baseline (approximately 1mm). These images are acquired
with the system NanEye Stereo manufactured by CMOSIS/AWAIBA. These stereo
cameras have also small apertures, which means that high levels of illumination
are required. The goal was to develop an approach yielding accurate
reconstructions, with a low computational cost, i.e., avoiding non-linear
numerical optimization algorithms. In particular we focused on the analysis and
comparison of radial distortion models. To perform the analysis and comparison,
we defined a baseline method based on available software and methods, such as
the Bouguet toolbox [2] or the Computer Vision Toolbox from Matlab. The
approaches tested were based on the use of the polynomial model of radial
distortion, and on the application of the division model. The issue of the
center of distortion was also addressed within the framework of the application
of the division model. We concluded that the division model with a single
radial distortion parameter has limitations
3D Reconstruction with Low Resolution, Small Baseline and High Radial Distortion Stereo Images
In this paper we analyze and compare approaches for 3D reconstruction from
low-resolution (250x250), high radial distortion stereo images, which are
acquired with small baseline (approximately 1mm). These images are acquired
with the system NanEye Stereo manufactured by CMOSIS/AWAIBA. These stereo
cameras have also small apertures, which means that high levels of illumination
are required. The goal was to develop an approach yielding accurate
reconstructions, with a low computational cost, i.e., avoiding non-linear
numerical optimization algorithms. In particular we focused on the analysis and
comparison of radial distortion models. To perform the analysis and comparison,
we defined a baseline method based on available software and methods, such as
the Bouguet toolbox [2] or the Computer Vision Toolbox from Matlab. The
approaches tested were based on the use of the polynomial model of radial
distortion, and on the application of the division model. The issue of the
center of distortion was also addressed within the framework of the application
of the division model. We concluded that the division model with a single
radial distortion parameter has limitations
Advancing In Situ Modeling of ICMEs: New Techniques for New Observations
It is generally known that multi-spacecraft observations of interplanetary
coronal mass ejections (ICMEs) more clearly reveal their three-dimensional
structure than do observations made by a single spacecraft. The launch of the
STEREO twin observatories in October 2006 has greatly increased the number of
multipoint studies of ICMEs in the literature, but this field is still in its
infancy. To date, most studies continue to use on flux rope models that rely on
single track observations through a vast, multi-faceted structure, which
oversimplifies the problem and often hinders interpretation of the large-scale
geometry, especially for cases in which one spacecraft observes a flux rope,
while another does not. In order to tackle these complex problems, new modeling
techniques are required. We describe these new techniques and analyze two ICMEs
observed at the twin STEREO spacecraft on 22-23 May 2007, when the spacecraft
were separated by ~8 degrees. We find a combination of non-force-free flux rope
multi-spacecraft modeling, together with a new non-flux rope ICME plasma flow
deflection model, better constrains the large-scale structure of these ICMEs.
We also introduce a new spatial mapping technique that allows us to put
multispacecraft observations and the new ICME model results in context with the
convecting solar wind. What is distinctly different about this analysis is that
it reveals aspects of ICME geometry and dynamics in a far more visually
intuitive way than previously accomplished. In the case of the 22-23 May ICMEs,
the analysis facilitates a more physical understanding of ICME large-scale
structure, the location and geometry of flux rope sub-structures within these
ICMEs, and their dynamic interaction with the ambient solar wind
Reconstructing CMEs with Coordinated Imaging and In Situ Observations: Global Structure, Kinematics, and Implications for Space Weather Forecasting
See the pdf for detailsComment: 45 pages, 16 figures, ApJ, in pres
Impact of lens distrortions on strain measurements obtained with digital image correlation
The determination of strain fields based on displacements obtained via DIC at the micro-strain level is still a cumbersome task. In particular when high-strain gradients are involved, e.g. in composite materials with multidirectional fibre reinforcement, uncertainties in the experimental setup and errors in the derivation of the displacement fields can substantially hamper the strain identification process. In this contribution, the aim is to investigate the impact of lens distortions on strain measurements. To this purpose, we first perform pure rigid body motion experiments, revealing the importance of precise correction of lens distortions. Next, a uni-axial tensile test on a textile composite with spatially varying high strain gradients is performed, resulting in very accurate determined strains along the fibers of the materia
Fast 3D reconstruction with single shot technology : engineering and computing challenges
Fast 3D reconstruction with single shot technology: the GMPR 3D scanning technologies provide fast wide area scanning from an instantaneous shot. A surface can be reconstructed in 40 milliseconds from a pattern of stripes projected on the target object. It operates on a single image or on a video sequence both in the near-infrared (NIR) and visible spectra. In this talk we are going to describe the engineering and computing principles behind the technologies, highlight the main achievements of our research to date and discuss a number of remaining challenge
Physics Of Eclipsing Binaries. II. Towards the Increased Model Fidelity
The precision of photometric and spectroscopic observations has been
systematically improved in the last decade, mostly thanks to space-borne
photometric missions and ground-based spectrographs dedicated to finding
exoplanets. The field of eclipsing binary stars strongly benefited from this
development. Eclipsing binaries serve as critical tools for determining
fundamental stellar properties (masses, radii, temperatures and luminosities),
yet the models are not capable of reproducing observed data well either because
of the missing physics or because of insufficient precision. This led to a
predicament where radiative and dynamical effects, insofar buried in noise,
started showing up routinely in the data, but were not accounted for in the
models. PHOEBE (PHysics Of Eclipsing BinariEs; http://phoebe-project.org) is an
open source modeling code for computing theoretical light and radial velocity
curves that addresses both problems by incorporating missing physics and by
increasing the computational fidelity. In particular, we discuss triangulation
as a superior surface discretization algorithm, meshing of rotating single
stars, light time travel effect, advanced phase computation, volume
conservation in eccentric orbits, and improved computation of local intensity
across the stellar surfaces that includes photon-weighted mode, enhanced limb
darkening treatment, better reflection treatment and Doppler boosting. Here we
present the concepts on which PHOEBE is built on and proofs of concept that
demonstrate the increased model fidelity.Comment: 60 pages, 15 figures, published in ApJS; accompanied by the release
of PHOEBE 2.0 on http://phoebe-project.or
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