2,915 research outputs found
Aperture Supervision for Monocular Depth Estimation
We present a novel method to train machine learning algorithms to estimate
scene depths from a single image, by using the information provided by a
camera's aperture as supervision. Prior works use a depth sensor's outputs or
images of the same scene from alternate viewpoints as supervision, while our
method instead uses images from the same viewpoint taken with a varying camera
aperture. To enable learning algorithms to use aperture effects as supervision,
we introduce two differentiable aperture rendering functions that use the input
image and predicted depths to simulate the depth-of-field effects caused by
real camera apertures. We train a monocular depth estimation network end-to-end
to predict the scene depths that best explain these finite aperture images as
defocus-blurred renderings of the input all-in-focus image.Comment: To appear at CVPR 2018 (updated to camera ready version
Recent Progress in Image Deblurring
This paper comprehensively reviews the recent development of image
deblurring, including non-blind/blind, spatially invariant/variant deblurring
techniques. Indeed, these techniques share the same objective of inferring a
latent sharp image from one or several corresponding blurry images, while the
blind deblurring techniques are also required to derive an accurate blur
kernel. Considering the critical role of image restoration in modern imaging
systems to provide high-quality images under complex environments such as
motion, undesirable lighting conditions, and imperfect system components, image
deblurring has attracted growing attention in recent years. From the viewpoint
of how to handle the ill-posedness which is a crucial issue in deblurring
tasks, existing methods can be grouped into five categories: Bayesian inference
framework, variational methods, sparse representation-based methods,
homography-based modeling, and region-based methods. In spite of achieving a
certain level of development, image deblurring, especially the blind case, is
limited in its success by complex application conditions which make the blur
kernel hard to obtain and be spatially variant. We provide a holistic
understanding and deep insight into image deblurring in this review. An
analysis of the empirical evidence for representative methods, practical
issues, as well as a discussion of promising future directions are also
presented.Comment: 53 pages, 17 figure
Colloidal particle motion as a diagnostic of DNA conformational transitions
Tethered particle motion is an experimental technique to monitor
conformational changes in single molecules of DNA in real time, by observing
the position fluctuations of a micrometer-size particle attached to the DNA.
This article reviews some recent work on theoretical problems inherent in the
interpretation of TPM experiments, both in equilibrium and dynamical aspects.Comment: 19pp. Accepted for publication in Curr Op Colloid Interf Scienc
Vainu Bappu Memorial Lecture: What is a sunspot?
Sunspots have been known in the West since Galileo Galilei and Thomas Harriot
first used telescopes to observe the Sun nearly four centuries ago; they have
been known to the Chinese for more than two thousand years. They appear as
relatively dark patches on the surface of the Sun, and are caused by
concentrations of magnetism which impede the flow of heat from deep inside the
Sun up to its othewise brilliant surface. The spots are not permanent: the
total number of spots on the Sun varies cyclically in time, with a period of
about eleven years, associated with which there appear to be variations in our
climate. When there are many spots, it is more dangerous for spacecraft to
operate. The cause of the spots is not well understood; nor is it known for
sure how they die. Their structure beneath the surface of the Sun is in some
dispute, although much is known about their properties at the surface,
including an outward material flow which was discovered by John Evershed
observing the Sun from Kodaikanal a hundred years ago. I shall give you a
glimpse of how we are striving to deepen our understanding of these fascinating
features, and of some of the phenomena that appear to be associated with them.Comment: Lecture delivered at the Indian Institute of Astrophysics, December
2008 Typing errors corrected To appear in Magnetic Coupling between the
Interior and the Atmosphere of the Sun, ed. S.S. Hasan & R.J. Rutten, Astr.
Sp. Sci. Pro
08291 Abstracts Collection -- Statistical and Geometrical Approaches to Visual Motion Analysis
From 13.07.2008 to 18.07.2008, the Dagstuhl Seminar 08291 ``Statistical and Geometrical Approaches to Visual Motion Analysis\u27\u27 was held in the International Conference and Research Center (IBFI), Schloss Dagstuhl.
During the seminar, several participants presented their current
research, and ongoing work and open problems were discussed. Abstracts of
the presentations given during the seminar as well as abstracts of
seminar results and ideas are put together in this paper. The first section
describes the seminar topics and goals in general
The 3-D shaping of NGC 6741: a massive, fast-evolving Planetary Nebula at the recombination--reionization edge
We infer the gas kinematics, diagnostics and ionic radial profiles, distance
and central star parameters, nebular photo- ionization model, spatial structure
and evolutionary phase of the PN NGC 6741 by means of long-slit high-resolution
spectra at nine position angles. NGC 6741 (distance ~2.0 kpc, age ~1400 yr,
ionized mass Mion ~0.06 Mo) is a dense (electron density up to 12,000 cm^(-3)),
high-excitation, almost- prolate ellipsoid, surrounded by a sharp
low-excitation skin (the ionization front), and embedded into a spherical
(radius ~ 0.080 pc), almost-neutral, high-density (n(HI) ~7 x 10^3 atoms
cm^(-3)) halo containing a large fraction of the nebular mass (Mhalo>0.20 Mo).
The kinematics, physical conditions and ionic structure indicate that NGC 6741
is in a deep recombination phase, started about 200 years ago, and caused by
the quick luminosity drop of the massive (M*=0.66-0.68 Mo), hot (logT* ~ 5.23)
and faint (log L*/Lo ~ 2.75) post--AGB star, which has exhausted the
hydrogen-shell nuclear burning and is moving along the white dwarf cooling
sequence. The general expansion law of the ionized gas in NGC 6741, Vexp (km
s^(-1)=13 x R", fails in the innermost, highest-excitation layers, which move
slower than expected. The observed deceleration is ascribable to the luminosity
drop of the central star, and appears in striking contrast to recent reports
inferring that acceleration is a common property of the Planetary Nebulae
innermost layers. Some general implications on the shaping mechanisms of
Planetary Nebulae are discussed.Comment: 27 pages, 18 figures, accepted for publication in A&A, movies of the
reconstructed nebula are available at http://web.pd.astro.it/sabbadin
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