Topic
Aperture
About: Aperture is a research topic. Over the lifetime, 44310 publications have been published within this topic receiving 467495 citations. The topic is also known as: diaphragm.
Papers published on a yearly basis
Papers
More filters
TL;DR: Computer simulations show that the URA with significant shot and background noise is vastly superior to random array techniques without noise, and permits a detector which is smaller than its random array counterpart.
Abstract: A system utilizing uniformly redundant arrays to image non-focusable radiation. The uniformly redundant array is used in conjunction with a balanced correlation technique to provide a system with no artifacts such that virtually limitless signal-to-noise ratio is obtained with high transmission characteristics. Additionally, the array is mosaicked to reduce required detector size over conventional array detectors.
866 citations
TL;DR: The resolving power of the electron microscope and the contrast in the image are calculated for different conditions of focusing, illumination and aperture as mentioned in this paper, which can change the limit of resolution by a factor of about 3.
Abstract: The resolving power of the electron microscope and the contrast in the image are calculated for different conditions of focusing, illumination and aperture. These conditions can change the limit of resolution by a factor of about 3. The contrast in the image of an atom is appreciably increased by defocusing and spherical aberration. Nevertheless, the contrast improves when the numerical value of the aberration constant is diminished. The effect of different methods of spherical correction is discussed briefly.
854 citations
Fermilab1, Ohio State University2, University College London3, Autonomous University of Barcelona4, University of Pennsylvania5, Carnegie Learning6, University of Michigan7, Institut de Ciències de l'Espai8, Texas A&M University9, Lawrence Berkeley National Laboratory10, University of Chicago11, University of Illinois at Urbana–Champaign12, Australian Astronomical Observatory13, Argonne National Laboratory14, SLAC National Accelerator Laboratory15, Catalan Institution for Research and Advanced Studies16, Institute of Cosmology and Gravitation, University of Portsmouth17, California Institute of Technology18, Brookhaven National Laboratory19, Stanford University20
TL;DR: The Dark Energy Camera as mentioned in this paper was designed and constructed by the Dark Energy Survey Collaboration, and meets or exceeds the stringent requirements designed for the wide-field and supernova surveys for which the collaboration uses it.
Abstract: The Dark Energy Camera is a new imager with a 2.2-degree diameter field of view mounted at the prime focus of the Victor M. Blanco 4-meter telescope on Cerro Tololo near La Serena, Chile. The camera was designed and constructed by the Dark Energy Survey Collaboration, and meets or exceeds the stringent requirements designed for the wide-field and supernova surveys for which the collaboration uses it. The camera consists of a five element optical corrector, seven filters, a shutter with a 60 cm aperture, and a CCD focal plane of 250 micron thick fully-depleted CCDs cooled inside a vacuum Dewar. The 570 Mpixel focal plane comprises 62 2kx4k CCDs for imaging and 12 2kx2k CCDs for guiding and focus. The CCDs have 15 microns x15 microns pixels with a plate scale of 0.263 arc sec per pixel. A hexapod system provides state-of-the-art focus and alignment capability. The camera is read out in 20 seconds with 6-9 electrons readout noise. This paper provides a technical description of the camera's engineering, construction, installation, and current status.
844 citations
23 Jun 1999
TL;DR: A simple algorithm is described that computes the radiometric response function of an imaging system, from images of an arbitrary scene taken using different exposures, to fuse the multiple images into a single high dynamic range radiance image.
Abstract: A simple algorithm is described that computes the radiometric response function of an imaging system, from images of an arbitrary scene taken using different exposures. The exposure is varied by changing either the aperture setting or the shutter speed. The algorithm does not require precise estimates of the exposures used. Rough estimates of the ratios of the exposures (e.g. F-number settings on an inexpensive lens) are sufficient for accurate recovery of the response function as well as the actual exposure ratios. The computed response function is used to fuse the multiple images into a single high dynamic range radiance image. Robustness is tested using a variety of scenes and cameras as well as noisy synthetic images generated using 100 randomly selected response curves. Automatic rejection of image areas that have large vignetting effects or temporal scene variations make the algorithm applicable to not just photographic but also video cameras.
837 citations
TL;DR: In this article, a ray-shooting approach is presented for calculating the interior radar cross section (RCS) from a partially open cavity, where a dense grid of rays is launched into the cavity through the opening.
Abstract: A ray-shooting approach is presented for calculating the interior radar cross section (RCS) from a partially open cavity. In the problem considered, a dense grid of rays is launched into the cavity through the opening. The rays bounce from the cavity walls based on the laws of geometrical optics and eventually exit the cavity via the aperture. The ray-bouncing method is based on tracking a large number of rays launched into the cavity through the opening and determining the geometrical optics field associated with each ray by taking into consideration: (1) the geometrical divergence factor, (2) polarization, and (3) material loading of the cavity walls. A physical optics scheme is then applied to compute the backscattered field from the exit rays. This method is so simple in concept that there is virtually no restriction on the shape or material loading of the cavity. Numerical results obtained by this method are compared with those for the modal analysis for a circular cylinder terminated by a PEC plate. RCS results for an S-bend circular cylinder generated on the Cray X-MP supercomputer show significant RCS reduction. Some of the limitations and possible extensions of this technique are discussed. >
831 citations