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Spatial calibration of an optical see-through head-mounted display
We present here a method for calibrating an optical see-through Head Mounted Display (HMD) using techniques usually applied to camera calibration (photogrammetry). Using a camera placed inside the HMD to take pictures simultaneously of a tracked object and features in the HMD display, we could exploit established camera calibration techniques to recover both the intrinsic and extrinsic properties of the~HMD (width, height, focal length, optic centre and principal ray of the display). Our method gives low re-projection errors and, unlike existing methods, involves no time-consuming and error-prone human measurements, nor any prior estimates about the HMD geometry
XMM-Newton observations of the hot spot galaxy NGC 2903
We report on the first deeper X-ray broad-band observation of the hot spot
galaxy NGC 2903 obtained with XMM-Newton. X-ray imaging and spectra of the
spiral barred galaxy were obtained from XMM-Newton archival data to study its
X-ray population and the conditions of the hot gas in its central region. We
investigate the spectral properties of the discrete point-source population and
give estimates of their X-ray spectral parameters. By analysing the RGS
spectra, we derive temperature and abundances for the hot gas located in its
central region. A total of six X-ray point sources (four of them ULX
candidates) were detected in the energy range of 0.3-10.0 keV located within
the galaxy D25 optical disk. Three of these sources are detected for the first
time, and one of them with a luminosity of higher than 10^39 erg/s. After
fitting three different models, we were able to estimate their luminosities,
which are compatible with those of binaries with a compact object in the form
of black holes (BHs) rather than neutron stars (NSs). We extracted the combined
first-order RGS1 and RGS2 spectra of its central region, which display several
emission lines. Both O\,{\sc vii} and lines seem to be of similar
strength, which is consistent with the presence of the collisionally ionized
gas that is typical of starburst galaxies. We fitted the spectrum to a model
for a plasma in collisional ionization equilibrium (CIE) and the continuum was
modelled with a power law, resulting in a plasma temperature of T = 0.31 \pm
0.01 keV and an emission measure EM \equiv n_Hn_eV =6.4_{-0.4}^{+0.5}\times
10^{61}^{-3}. We also estimated abundances that are consistent with solar
values.Comment: 5 pages, 2 figures, accepted for publication in A&A, resubmission
corrects typographical errors and improves exposition according to the
referee's suggestion
Stereo Matching in the Presence of Sub-Pixel Calibration Errors
Stereo matching commonly requires rectified images that are computed from calibrated cameras. Since all under-lying parametric camera models are only approximations, calibration and rectification will never be perfect. Additionally, it is very hard to keep the calibration perfectly stable in application scenarios with large temperature changes and vibrations. We show that even small calibration errors of a quarter of a pixel are severely amplified on certain structures. We discuss a robotics and a driver assistance example where sub-pixel calibration errors cause severe problems. We propose a filter solution based on signal theory that removes critical structures and makes stereo algorithms less sensitive to calibration errors. Our approach does not aim to correct decalibration, but rather to avoid amplifications and mismatches. Experiments on ten stereo pairs with ground truth and simulated decalibrations as well as images from robotics and driver assistance scenarios demonstrate the success and limitations of our solution that can be combined with any stereo method
Real-time 3D Tracking of Articulated Tools for Robotic Surgery
In robotic surgery, tool tracking is important for providing safe tool-tissue
interaction and facilitating surgical skills assessment. Despite recent
advances in tool tracking, existing approaches are faced with major
difficulties in real-time tracking of articulated tools. Most algorithms are
tailored for offline processing with pre-recorded videos. In this paper, we
propose a real-time 3D tracking method for articulated tools in robotic
surgery. The proposed method is based on the CAD model of the tools as well as
robot kinematics to generate online part-based templates for efficient 2D
matching and 3D pose estimation. A robust verification approach is incorporated
to reject outliers in 2D detections, which is then followed by fusing inliers
with robot kinematic readings for 3D pose estimation of the tool. The proposed
method has been validated with phantom data, as well as ex vivo and in vivo
experiments. The results derived clearly demonstrate the performance advantage
of the proposed method when compared to the state-of-the-art.Comment: This paper was presented in MICCAI 2016 conference, and a DOI was
linked to the publisher's versio
Morphological study of skin cancer lesions through a 3D scanner based on fringe projection and machine learning
Postprint (published version
High Resolution X-Ray Imaging of the Center of IC342
We presented the result of a high resolution (FWHM~0.5'') 12 ks Chandra HRC-I
observation of the starburst galaxy IC342 taken on 2 April 2006. We identified
23 X-ray sources within the central 30' x 30' region of IC342. Our HRC-I
observation resolved the historical Ultraluminous X-ray sources (ULX), X3, near
the nucleus into 2 sources, namely C12 and C13, for the first time. The
brighter source C12, with L(0.08-10keV)=(6.66\pm0.45)\times10^{38}ergs^-1, was
spatially extended (~82 pc x 127 pc). From the astrometric registration of the
X-ray image, C12 was at R.A.=03h:46m:48.43s, decl.=+68d05m47.45s, and was
closer to the nucleus than C13. Thus we concluded that source was not an ULX
and must instead be associated with the nucleus. The fainter source C13, with
L(0.08-10keV)=(5.1\pm1.4) x 10^{37}ergs^-1 was consistent with a point source
and located $6.51'' at P.A. 240 degree of C12.
We also analyzed astrometrically corrected optical Hubble Space Telescope and
radio Very Large Array images, a comparison with the X-ray image showed
similarities in their morphologies. Regions of star formation within the
central region of IC342 were clearly visible in HST H alpha image and this was
the region where 3 optical star clusters and correspondingly our detected X-ray
source C12 were observed. We found that a predicted X-ray emission from
starburst was very close to the observed X-ray luminosity of C12, suggesting
that nuclear X-ray emission in IC342 was dominated by starburst. Furthermore,
we discussed the possibility of AGN in the nucleus of IC342. Although our data
was not enough to give a firm existence of an AGN, it could not be discarded.Comment: 29 page, 8 figures, accepted by Ap
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