23,704 research outputs found
Review: Extending Visible Band Computer Vision Techniques to Infrared Band Images
Infared imaging process bears many similarities to the visible imaging process. If visible band computer vision techniques can be used on infrared images with no or small adjustments it would save us the trouble of redeveloping a whole new set of techniques. However, there are important differences in the practical environmental parameters between visible and infrared bands that invalidates many convenient background assumptions inherent to visible-band computer vision techniques. We review here the underlying reasons why some computer vision techniques can while some cannot be applied directly to infrared images. We also examine a few attempts to extend computer vision to infrared images and discuss their relative merits
A study to determine the optimum design of a photographic film for the lunar surface hand-held camera Final report
Design, and processing of photographic film for lunar surface hand operated camer
Optical Properties of Correlated Materials -- or Why Intelligent Windows may look Dirty
Materials with strong electronic Coulomb correlations play an increasing role
in modern materials applications. "Thermochromic" systems, which exhibit
thermally induced changes in their optical response, provide a particularly
interesting case. The optical switching associated with the metal-insulator
transition of vanadium dioxide, for example, has been proposed for use in
numerous applications, ranging from anti-laser shields to "intelligent"
windows, which selectively filter radiative heat in hot weather conditions. Are
present-day electronic structure techniques able to describe, or -- eventually
even predict -- such a kind of behavior ? How far are we from materials design
using correlated oxides ? These are the central questions we try to address in
this article. We review recent attempts of calculating optical properties of
correlated materials within dynamical mean field theory, and summarize results
for vanadium dioxide obtained within a novel scheme aiming at particularly
simple and efficient calculations of optical transition matrix elements within
localized basis sets. Finally, by optimizing the geometry of "intelligent
windows", we argue that this kind of technique can in principle be used to
provide guidance for experiments, thus giving a rather optimistic answer to the
above questions.Comment: 11 pages, 4 figures, Phys. Status Solidi B 246, in print (2009), also
available as psi-k Scientific Highlight of the Month, no. 88, August 2008,
http://www.psi-k.org/newsletters/News_88/Highlight_88.pd
Digital Color Imaging
This paper surveys current technology and research in the area of digital
color imaging. In order to establish the background and lay down terminology,
fundamental concepts of color perception and measurement are first presented
us-ing vector-space notation and terminology. Present-day color recording and
reproduction systems are reviewed along with the common mathematical models
used for representing these devices. Algorithms for processing color images for
display and communication are surveyed, and a forecast of research trends is
attempted. An extensive bibliography is provided
Is the Pale Blue Dot unique? Optimized photometric bands for identifying Earth-like exoplanets
The next generation of ground and space-based telescopes will image habitable
planets around nearby stars. A growing literature describes how to characterize
such planets with spectroscopy, but less consideration has been given to the
usefulness of planet colors. Here, we investigate whether potentially
Earth-like exoplanets could be identified using UV-visible-to-NIR wavelength
broadband photometry (350-1000 nm). Specifically, we calculate optimal
photometric bins for identifying an exo-Earth and distinguishing it from
uninhabitable planets including both Solar System objects and model exoplanets.
The color of some hypothetical exoplanets - particularly icy terrestrial worlds
with thick atmospheres - is similar to Earth's because of Rayleigh scattering
in the blue region of the spectrum. Nevertheless, subtle features in Earth's
reflectance spectrum appear to be unique. In particular, Earth's reflectance
spectrum has a 'U-shape' unlike all our hypothetical, uninhabitable planets.
This shape is partly biogenic because O2-rich, oxidizing air is transparent to
sunlight, allowing prominent Rayleigh scattering, while ozone absorbs visible
light, creating the bottom of the 'U'. Whether such uniqueness has practical
utility depends on observational noise. If observations are photon limited or
dominated by astrophysical sources (zodiacal light or imperfect starlight
suppression), then the use of broadband visible wavelength photometry to
identify Earth twins has little practical advantage over obtaining detailed
spectra. However, if observations are dominated by dark current then optimized
photometry could greatly assist preliminary characterization. We also calculate
the optimal photometric bins for identifying extrasolar Archean Earths, and
find that the Archean Earth is more difficult to unambiguously identify than a
modern Earth twin.Comment: 10 figures, 38 page
Multimodal Imaging of Photoreceptor Structure in Choroideremia
Purpose
Choroideremia is a progressive X-linked recessive dystrophy, characterized by degeneration of the retinal pigment epithelium (RPE), choroid, choriocapillaris, and photoreceptors. We examined photoreceptor structure in a series of subjects with choroideremia with particular attention to areas bordering atrophic lesions. Methods
Twelve males with clinically-diagnosed choroideremia and confirmed hemizygous mutations in the CHM gene were examined. High-resolution images of the retina were obtained using spectral domain optical coherence tomography (SD-OCT) and both confocal and non-confocal split-detector adaptive optics scanning light ophthalmoscope (AOSLO) techniques. Results
Eleven CHM gene mutations (3 novel) were identified; three subjects had the same mutation and one subject had two mutations. SD-OCT findings included interdigitation zone (IZ) attenuation or loss in 10/12 subjects, often in areas with intact ellipsoid zones; RPE thinning in all subjects; interlaminar bridges in the imaged areas of 10/12 subjects; and outer retinal tubulations (ORTs) in 10/12 subjects. Only split-detector AOSLO could reliably resolve cones near lesion borders, and such cones were abnormally heterogeneous in morphology, diameter and density. On split-detector imaging, the cone mosaic terminated sharply at lesion borders in 5/5 cases examined. Split-detector imaging detected remnant cone inner segments within ORTs, which were generally contiguous with a central patch of preserved retina. Conclusions
Early IZ dropout and RPE thinning on SD-OCT are consistent with previously published results. Evidence of remnant cone inner segments within ORTs and the continuity of the ORTs with preserved retina suggests that these may represent an intermediate state of retinal degeneration prior to complete atrophy. Taken together, these results supports a model of choroideremia in which the RPE degenerates before photoreceptors
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