23,560 research outputs found
Multi-spectral materials: hybridisation of optical plasmonic filters and a terahertz metamaterial absorber
Multi-spectral materials, using hybridised plasmonic and metamaterial structures, can simultaneously exhibit unique resonant phenomena over several decades of wavelengths. A multi-spectral material that combines a plasmonic colour filter array and a terahertz metamaterial absorber into a single material is a promising prospect for a coaxial multi-spectral imager operating in the visible, near IR, and terahertz wavebands
Hybridization of optical plasmonics with terahertz metamaterials to create multi-spectral filters
Multi-spectral imaging systems typically require the cumbersome integration of disparate filtering materials in order to work simultaneously in multiple spectral regions. We show for the first time how a single nano-patterned metal film can be used to filter multi-spectral content from the visible, near infrared and terahertz bands by hybridizing plasmonics and metamaterials. Plasmonic structures are well-suited to the visible band owing to the resonant dielectric properties of metals, whereas metamaterials are preferable at terahertz frequencies where metal conductivity is high. We present the simulated and experimental characteristics of our new hybrid synthetic multi-spectral material filters and demonstrate the independence of the metamaterial and plasmonic responses with respect to each other
Registration and Fusion of Multi-Spectral Images Using a Novel Edge Descriptor
In this paper we introduce a fully end-to-end approach for multi-spectral
image registration and fusion. Our method for fusion combines images from
different spectral channels into a single fused image by different approaches
for low and high frequency signals. A prerequisite of fusion is a stage of
geometric alignment between the spectral bands, commonly referred to as
registration. Unfortunately, common methods for image registration of a single
spectral channel do not yield reasonable results on images from different
modalities. For that end, we introduce a new algorithm for multi-spectral image
registration, based on a novel edge descriptor of feature points. Our method
achieves an accurate alignment of a level that allows us to further fuse the
images. As our experiments show, we produce a high quality of multi-spectral
image registration and fusion under many challenging scenarios
Characterization of color cross-talk of CCD detectors and its influence in multispectral quantitative phase imaging
Multi-spectral quantitative phase imaging (QPI) is an emerging imaging
modality for wavelength dependent studies of several biological and industrial
specimens. Simultaneous multi-spectral QPI is generally performed with color
CCD cameras. However, color CCD cameras are suffered from the color crosstalk
issue, which needed to be explored. Here, we present a new approach for
accurately measuring the color crosstalk of 2D area detectors, without needing
prior information about camera specifications. Color crosstalk of two different
cameras commonly used in QPI, single chip CCD (1-CCD) and three chip CCD
(3-CCD), is systematically studied and compared using compact interference
microscopy. The influence of color crosstalk on the fringe width and the
visibility of the monochromatic constituents corresponding to three color
channels of white light interferogram are studied both through simulations and
experiments. It is observed that presence of color crosstalk changes the fringe
width and visibility over the imaging field of view. This leads to an unwanted
non-uniform background error in the multi-spectral phase imaging of the
specimens. It is demonstrated that the color crosstalk of the detector is the
key limiting factor for phase measurement accuracy of simultaneous
multi-spectral QPI systems.Comment: 16 pages, 8 figure
PeX 1. Multi-spectral expansion of residual speckles for planet detection
The detection of exoplanets in coronographic images is severely limited by
residual starlight speckles. Dedicated post-processing can drastically reduce
this "stellar leakage" and thereby increase the faintness of detectable
exoplanets. Based on a multi-spectral series expansion of the diffraction
pattern, we derive a multi-mode model of the residuals which can be exploited
to estimate and thus remove the residual speckles in multi-spectral
coronographic images. Compared to other multi-spectral processing methods, our
model is physically grounded and is suitable for use in an (optimal) inverse
approach. We demonstrate the ability of our model to correctly estimate the
speckles in simulated data and demonstrate that very high contrasts can be
achieved. We further apply our method to removing speckles from a real data
cube obtained with the SPHERE IFS instrument.Comment: accepted for publication in MNRAS on 25th of August 2017, 17 pages,
15 figure
Low-degree multi-spectral p-mode fitting
We combine unresolved-Sun velocity and intensity observations at multiple wavelengths from the Helioseismic and Magnetic Imager and Atmospheric Imaging Array onboard the Solar Dynamics Observatory to investigate the possibility of multi-spectral mode-frequency estimation at low spherical harmonic degree. We test a simple multi-spectral algorithm using a common line width and frequency for each mode and a separate amplitude, background and asymmetry parameter, and compare the results with those from fits to the individual spectra. The preliminary results suggest that this approach may provide a more stable fit than using the observables separately
MAPCAT: Monitoring AGN with Polarimetry at the Calar Alto Telescopes
We introduce MAPCAT, a long-term observing program for "Monitoring of AGN
with Polarimetry at the Calar Alto Telescopes". Multi-spectral-range studies
are critical to understand some of the most relevant current problems of high
energy astrophysics of blazars such as their high energy emission mechanisms
and the location of their gamma-ray emission region through event associations
across the spectrum. Adding multi-spectral-range polarimetry allows for even
more reliable identification of polarized flares across the spectrum in these
kind of objects, as well as for more accurate modeling of their magnetic field.
As part of a major international effort to study the long term multi-spectral
range polarimetric behavior of blazars, MAPCAT uses -since mid 2007- CAFOS on
the 2.2m Telescope at the Calar Alto Observatory (Almeria, Spain) to obtain
monthly optical (R-band) photo-polarimetric measurements of a sample of 34 of
the brightest gamma-ray, optical, and radio-millimeter blazars accessible from
the northern hemisphere.Comment: To be published in the proceedings of High Energy Phenomena in
Relativistic Outflows III (HEPRO III, IJMPCS). 4 page
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