7,105 research outputs found
High-contrast spectroscopy of SCR J1845-6357 B
Spectral characterization of sub-stellar companions is essential to
understand their composition and formation processes. However, the large
contrast ratio of the brightness of each object to that of its parent star
limits our ability to extract a clean spectrum, free from any significant
contribution from the star. During the development of the long slit
spectroscopy (LSS) mode of IRDIS, the dual-band imager and spectrograph of
SPHERE, we proposed a data analysis method to estimate and remove the
contributions of the stellar spectrum. This method has never been tested on
real data because of the lack of instrumentation capable of combining adaptive
optics (AO), coronagraphy, and LSS. Nonetheless, a similar attenuation of the
star can be obtained using a particular observing configuration. Test data were
acquired using the AO-assisted spectrograph VLT/NACO. We obtained new J- and
H-band spectra of SCR J1845-6357 B, a T6 companion to a nearby (3.85\pm0.02 pc)
M8 star. This system is a well-suited benchmark as it is relatively wide
(~1.0") with a modest contrast ratio (~4 mag), and a previously published JHK
spectrum is available for reference. We demonstrate that (1) our method is
efficient at estimating and removing the stellar contribution, (2) it allows to
properly recover the spectral shape of the companion, and (3) it is essential
to obtain an unbiased estimation of physical parameters. We also show that the
slit configuration associated with this method allows us to use long exposure
times with high throughput producing high signal-to-noise ratio data. However,
the signal of the companion gets over-subtracted, particularly in our J-band
data, compelling us to use a fake companion spectrum to estimate and compensate
for the loss of flux. Finally, we report a new astrometric measurement of the
position of the companion (sep = 0.817", PA = 227.92 deg).Comment: 11 pages, 8 figures, 4 tables. Accepted for publication in A&
Real-time detection and tracking of multiple objects with partial decoding in H.264/AVC bitstream domain
In this paper, we show that we can apply probabilistic spatiotemporal
macroblock filtering (PSMF) and partial decoding processes to effectively
detect and track multiple objects in real time in H.264|AVC bitstreams with
stationary background. Our contribution is that our method cannot only show
fast processing time but also handle multiple moving objects that are
articulated, changing in size or internally have monotonous color, even though
they contain a chaotic set of non-homogeneous motion vectors inside. In
addition, our partial decoding process for H.264|AVC bitstreams enables to
improve the accuracy of object trajectories and overcome long occlusion by
using extracted color information.Comment: SPIE Real-Time Image and Video Processing Conference 200
Recommended from our members
Multiview System for Tracking a Fast Moving Object Against Complex Backgrounds
Tracking the real world coordinate of a fast moving object against a complex background is very challenging. When designing a multi-view system for this purpose, one key consideration is the arrangement of the cameras such that the object can be constantly and accurately tracked. This paper discusses a novel cameras arrangement, which can provide redundancy for fault tolerance, yet do not require installing more cameras nor relying aerial views of the scene. Using a table tennis match as example, experiment results show that the multi-view system with this cameras arrangement has a promising potential for tracking a table tennis ball in a real match scene
Towards real-time body pose estimation for presenters in meeting environments
This paper describes a computer vision-based approach to body pose estimation.\ud
The algorithm can be executed in real-time and processes low resolution,\ud
monocular image sequences. A silhouette is extracted and matched against a\ud
projection of a 16 DOF human body model. In addition, skin color is used to\ud
locate hands and head. No detailed human body model is needed. We evaluate the\ud
approach both quantitatively using synthetic image sequences and qualitatively\ud
on video test data of short presentations. The algorithm is developed with the\ud
aim of using it in the context of a meeting room where the poses of a presenter\ud
have to be estimated. The results can be applied in the domain of virtual\ud
environments
- …