15,514 research outputs found
Receptive Field Block Net for Accurate and Fast Object Detection
Current top-performing object detectors depend on deep CNN backbones, such as
ResNet-101 and Inception, benefiting from their powerful feature
representations but suffering from high computational costs. Conversely, some
lightweight model based detectors fulfil real time processing, while their
accuracies are often criticized. In this paper, we explore an alternative to
build a fast and accurate detector by strengthening lightweight features using
a hand-crafted mechanism. Inspired by the structure of Receptive Fields (RFs)
in human visual systems, we propose a novel RF Block (RFB) module, which takes
the relationship between the size and eccentricity of RFs into account, to
enhance the feature discriminability and robustness. We further assemble RFB to
the top of SSD, constructing the RFB Net detector. To evaluate its
effectiveness, experiments are conducted on two major benchmarks and the
results show that RFB Net is able to reach the performance of advanced very
deep detectors while keeping the real-time speed. Code is available at
https://github.com/ruinmessi/RFBNet.Comment: Accepted by ECCV 201
A Comprehensive Performance Evaluation of Deformable Face Tracking "In-the-Wild"
Recently, technologies such as face detection, facial landmark localisation
and face recognition and verification have matured enough to provide effective
and efficient solutions for imagery captured under arbitrary conditions
(referred to as "in-the-wild"). This is partially attributed to the fact that
comprehensive "in-the-wild" benchmarks have been developed for face detection,
landmark localisation and recognition/verification. A very important technology
that has not been thoroughly evaluated yet is deformable face tracking
"in-the-wild". Until now, the performance has mainly been assessed
qualitatively by visually assessing the result of a deformable face tracking
technology on short videos. In this paper, we perform the first, to the best of
our knowledge, thorough evaluation of state-of-the-art deformable face tracking
pipelines using the recently introduced 300VW benchmark. We evaluate many
different architectures focusing mainly on the task of on-line deformable face
tracking. In particular, we compare the following general strategies: (a)
generic face detection plus generic facial landmark localisation, (b) generic
model free tracking plus generic facial landmark localisation, as well as (c)
hybrid approaches using state-of-the-art face detection, model free tracking
and facial landmark localisation technologies. Our evaluation reveals future
avenues for further research on the topic.Comment: E. Antonakos and P. Snape contributed equally and have joint second
authorshi
Self-coherent camera as a focal plane wavefront sensor: simulations
Direct detection of exoplanets requires high dynamic range imaging.
Coronagraphs could be the solution, but their performance in space is limited
by wavefront errors (manufacturing errors on optics, temperature variations,
etc.), which create quasi-static stellar speckles in the final image. Several
solutions have been suggested for tackling this speckle noise. Differential
imaging techniques substract a reference image to the coronagraphic residue in
a post-processing imaging. Other techniques attempt to actively correct
wavefront errors using a deformable mirror. In that case, wavefront aberrations
have to be measured in the science image to extremely high accuracy. We propose
the self-coherent camera sequentially used as a focal-plane wavefront sensor
for active correction and differential imaging. For both uses, stellar speckles
are spatially encoded in the science image so that differential aberrations are
strongly minimized. The encoding is based on the principle of light incoherence
between the hosting star and its environment. In this paper, we first discuss
one intrinsic limitation of deformable mirrors. Then, several parameters of the
self-coherent camera are studied in detail. We also propose an easy and robust
design to associate the self-coherent camera with a coronagraph that uses a
Lyot stop. Finally, we discuss the case of the association with a four-quadrant
phase mask and numerically demonstrate that such a device enables the detection
of Earth-like planets under realistic conditions. The parametric study of the
technique lets us believe it can be implemented quite easily in future
instruments dedicated to direct imaging of exoplanets.Comment: 15 pages, 14 figures, accepted in A&A (here is the final version
NFIRAOS First Facility AO System for the Thirty Meter Telescope
NFIRAOS, the Thirty Meter Telescope's first adaptive optics system is an
order 60x60 Multi-Conjugate AO system with two deformable mirrors. Although
most observing will use 6 laser guide stars, it also has an NGS-only mode.
Uniquely, NFIRAOS is cooled to -30 C to reduce thermal background. NFIRAOS
delivers a 2-arcminute beam to three client instruments, and relies on up to
three IR WFSs in each instrument. We present recent work including: robust
automated acquisition on these IR WFSs; trade-off studies for a common-size of
deformable mirror; real-time computing architectures; simplified designs for
high-order NGS-mode wavefront sensing; modest upgrade concepts for
high-contrast imaging.Comment: ..submitted to SPIE 9148 Astronomical Telescopes and Instrumentation
- Adaptive Optics Systems IV (2014
- …