5,591 research outputs found
A Novel Framework for Highlight Reflectance Transformation Imaging
We propose a novel pipeline and related software tools for processing the multi-light image collections (MLICs) acquired in different application contexts to obtain shape and appearance information of captured surfaces, as well as to derive compact relightable representations of them. Our pipeline extends the popular Highlight Reflectance Transformation Imaging (H-RTI) framework, which is widely used in the Cultural Heritage domain. We support, in particular, perspective camera modeling, per-pixel interpolated light direction estimation, as well as light normalization correcting vignetting and uneven non-directional illumination. Furthermore, we propose two novel easy-to-use software tools to simplify all processing steps. The tools, in addition to support easy processing and encoding of pixel data, implement a variety of visualizations, as well as multiple reflectance-model-fitting options. Experimental tests on synthetic and real-world MLICs demonstrate the usefulness of the novel algorithmic framework and the potential benefits of the proposed tools for end-user applications.Terms: "European Union (EU)" & "Horizon 2020" / Action: H2020-EU.3.6.3. - Reflective societies - cultural heritage and European identity / Acronym: Scan4Reco / Grant number: 665091DSURF project (PRIN 2015) funded by the Italian Ministry of University and ResearchSardinian Regional Authorities under projects VIGEC and Vis&VideoLa
Perfect Anomalous Reflection with a Binary Huygens' Metasurface
In this paper we propose a new metasurface that is able to reflect a known
incoming electromagnetic wave into an arbitrary direction, with perfect power
efficiency. This seemingly simple task, which we hereafter call perfect
anomalous reflection, is actually highly non-trivial due to the differing wave
impedances and complex interference between the incident and reflected waves.
Heretofore, proposed metasurfaces which achieve perfect anomalous reflection
require complicated, deeply subwavelength and/or multilayer element structures
which allow them to couple to and from leaky and/or evanescent waves. In
contrast, we demonstrate that using a Binary Huygens' Metasurface (BHM) --- a
passive and lossless metasurface with only two cells per period --- perfect
anomalous reflection can be achieved over a wide angular and frequency range.
Through simulations and experiments at 24 GHz, we show that a properly designed
BHM can anomalously reflect an incident electromagnetic wave from to , with perfect power efficiency to within
experimental precision
Towards retrieving force feedback in robotic-assisted surgery: a supervised neuro-recurrent-vision approach
Robotic-assisted minimally invasive surgeries have gained a lot of popularity over conventional procedures as they offer many benefits to both surgeons and patients. Nonetheless, they still suffer from some limitations that affect their outcome. One of them is the lack of force feedback which restricts the surgeon's sense of touch and might reduce precision during a procedure. To overcome this limitation, we propose a novel force estimation approach that combines a vision based solution with supervised learning to estimate the applied force and provide the surgeon with a suitable representation of it. The proposed solution starts with extracting the geometry of motion of the heart's surface by minimizing an energy functional to recover its 3D deformable structure. A deep network, based on a LSTM-RNN architecture, is then used to learn the relationship between the extracted visual-geometric information and the applied force, and to find accurate mapping between the two. Our proposed force estimation solution avoids the drawbacks usually associated with force sensing devices, such as biocompatibility and integration issues. We evaluate our approach on phantom and realistic tissues in which we report an average root-mean square error of 0.02 N.Peer ReviewedPostprint (author's final draft
Photometric Variability in Earthshine Observations
The identification of an extrasolar planet as Earth-like will depend on the
detection of atmospheric signatures or surface non-uniformities. In this paper
we present spatially unresolved flux light curves of Earth for the purpose of
studying a prototype extrasolar terrestrial planet. Our monitoring of the
photometric variability of earthshine revealed changes of up to 23 % per hour
in the brightness of Earth's scattered light at around 600 nm, due to the
removal of specular reflection from the view of the Moon. This variability is
accompanied by reddening of the spectrum, and results from a change in surface
properties across the continental boundary between the Indian Ocean and
Africa's east coast. Our results based on earthshine monitoring indicate that
specular reflection should provide a useful tool in determining the presence of
liquid water on extrasolar planets via photometric observations.Comment: To appear in Astrobiology 9(3). 17 pages, 3 figures, 1 tabl
Low levels of specularity support operational color constancy, particularly when surface and illumination geometry can be inferred
We tested whether surface specularity alone supports operational color constancy—the ability to discriminate changes in illumination or reflectance. Observers viewed short animations of illuminant or reflectance changes in rendered scenes containing a single spherical surface and were asked to classify the change. Performance improved with increasing specularity, as predicted from regularities in chromatic statistics. Peak performance was impaired by spatial rearrangements of image pixels that disrupted the perception of illuminated surfaces but was maintained with increased surface complexity. The characteristic chromatic transformations that are available with nonzero specularity are useful for operational color constancy, particularly if accompanied by appropriate perceptual organization
GINA - A Polarized Neutron Reflectometer at the Budapest Neutron Centre
The setup, capabilities and operation parameters of the neutron reflectometer
GINA, the recently installed "Grazing Incidence Neutron Apparatus" at the
Budapest Neutron Centre, are introduced. GINA, a dance-floor-type,
constant-energy, angle-dispersive reflectometer is equipped with a 2D
position-sensitive detector to study specular and off-specular scattering.
Wavelength options between 3.2 and 5.7 {\AA} are available for unpolarized and
polarized neutrons. Spin polarization and analysis are achieved by magnetized
transmission supermirrors and radio-frequency adiabatic spin flippers. As a
result of vertical focusing by the five-element (pyrolytic graphite)
monochromator the reflected intensity from a 20x20 mm sample has doubled. GINA
is dedicated to studies of magnetic films and heterostructures, but unpolarized
options for non-magnetic films, membranes and other surfaces are also provided.
Shortly after its startup, reflectivity values as low as 3x10-5 have been
measured on the instrument. The facility is now open for the international user
community, but its development is continuing mainly to establish new sample
environment options, the spin analysis of off-specularly scattered radiation
and further decrease of the background
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