Observed Image (observed + image)

Distribution by Scientific Domains


Selected Abstracts


Shadow removal from image of stained glass windows

INTERNATIONAL JOURNAL OF IMAGING SYSTEMS AND TECHNOLOGY, Issue 3 2010
Shanmugalingam Suganthan
Abstract Shadows may be formed on stained glass windows by structural bars supporting the leaded panels, or by external protective wire grilles, or by masonry, such as mullions or buttresses, or external objects, such as trees. The eye tends to "discount" such shadow formations when viewing the actual windows even though in the photographic images they are very clearly visible. This article introduces a method to remove shadow effects on stained-glass windows; the observed image, as captured by the camera, may be modeled mathematically as a combination of a "true stained glass image" and a "grille/bar image." A mixture model is derived, based on a theoretical model of image formation, leading to a conjectured relationship between "shadow" pixels and the neighboring "nonshadow" pixels. The resulting mixture model assumes a multiplicative relationship. If this mixture can be separated into its original components, then it should be possible to remove the unwanted shadow component from the captured image to produce the desired image of the stained glass without the shadows. The digital modeling techniques enable the shadows to be characterized and removed with a reasonable degree of success. © 2010 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 20, 223,226, 2010. [source]


Orientational analysis of planar fibre systems observed as a Poisson shot-noise process

JOURNAL OF MICROSCOPY, Issue 1 2007
SALME KÄRKKÄINEN
Summary We consider two-dimensional fibrous materials observed as a digital greyscale image. The problem addressed is to estimate the orientation distribution of unobservable thin fibres from a greyscale image modelled by a planar Poisson shot-noise process. The classical stereological approach is not straightforward, because the point intensities of thin fibres along sampling lines may not be observable. For such cases, Kärkkäinen et al. (2001) suggested the use of scaled variograms determined from grey values along sampling lines in several directions. Their method is based on the assumption that the proportion between the scaled variograms and point intensities in all directions of sampling lines is constant. This assumption is proved to be valid asymptotically for Boolean models and dead leaves models, under some regularity conditions. In this work, we derive the scaled variogram and its approximations for a planar Poisson shot-noise process using the modified Bessel function. In the case of reasonable high resolution of the observed image, the scaled variogram has an approximate functional relation to the point intensity, and in the case of high resolution the relation is proportional. As the obtained relations are approximative, they are tested on simulations. The existing orientation analysis method based on the proportional relation is further experimented on images with different resolutions. The new result, the asymptotic proportionality between the scaled variograms and the point intensities for a Poisson shot-noise process, completes the earlier results for the Boolean models and for the dead leaves models. [source]


Azimuthal anisotropy of light extraction from photonic crystal light-emitting diodes

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2008
Chun-Feng Lai
Abstract Photonic crystal (PhC) light-emitting diodes (LEDs) exhibiting anisotropic light extraction have been investigated experimentally and theoretically. It is found that the anisotropic light extraction strongly depends on the lattice constant and orientation. Optical images of the anisotropy in the azimuthal direction are obtained using annular structure with triangular lattice. 6-fold symmetric light extraction patterns with varying number of petals are observed. More petals in multiple of 6 appear in the observed image with lattice constant increasing. This anisotropic behavior suggests a new means to optimize the PhC design of GaN LED for light extraction. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


A generalization of the mass-sheet degeneracy producing ring-like artefacts in the lens mass distribution

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2008
J. Liesenborgs
ABSTRACT The inversion of a gravitational lens system is, as is well known, plagued by the so-called mass-sheet degeneracy: one can always rescale the density distribution of the lens and add a constant-density mass sheet such that the, also properly rescaled, source plane is projected on to the same observed images. For strong lensing systems, it is often claimed that this degeneracy is broken as soon as two or more sources at different redshifts are available. This is definitely true in the strict sense that it is then impossible to add a constant-density mass sheet to the rescaled density of the lens without affecting the resulting images. However, often one can easily construct a more general mass distribution , instead of a constant-density sheet of mass , which gives rise to the same effect: a uniform scaling of the sources involved without affecting the observed images. We show that this can be achieved by adding one or more circularly symmetric mass distributions, each with its own centre of symmetry, to the rescaled mass distribution of the original lens. As it uses circularly symmetric distributions, this procedure can lead to the introduction of ring-shaped features in the mass distribution of the lens. In this paper, we show explicitly how degenerate inversions for a given strong lensing system can be constructed. It then becomes clear that many constraints are needed to effectively break this degeneracy. [source]