Topic
Parabolic reflector
About: Parabolic reflector is a research topic. Over the lifetime, 3375 publications have been published within this topic receiving 30735 citations. The topic is also known as: paraboloid reflector & paraboloidal reflector.
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TL;DR: In this paper, it was shown that for offset parabolic reflectors and for feeds located at the focal point, the predicted far field patterns (amplitude) by the GO/aperture field method will always be symmetric even in the offset plane.
Abstract: Both geometrical optics (GO)/aperture-field and physical-optics (PO) methods are used extensively in the diffraction analysis of offset parabolic and dual reflectors. An analytical/numerical comparative study is performed to demonstrate the limitations of the GO/aperture-field method for accurately predicting the sidelobe and null positions and levels. In particular, it is shown that for offset parabolic reflectors and for feeds located at the focal point, the predicted far-field patterns (amplitude) by the GO/aperture-field method will always be symmetric even in the offset plane. This, of course, is inaccurate fur the general case and it is shown that the physical-optics method can result in asymmetric patterns for cases in which the feed is located at the focal point. Representative numerical data are presented and a comparison is made with available measured data.
66 citations
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TL;DR: The solution shows that for an infinite paraboloid the confinement of the focused energy worsens, with the energy distribution spreading in the focal plane, and the structure of the field distribution in the vicinity of the focus strongly depends on the wavelength of the illumination.
Abstract: We derive a solution to the problem of a plane electromagnetic wave focused by a parabolic mirror. The solution is obtained from the Stratton-Chu integral by solving a boundary-value problem. Our solution can be considered self-consistent. We also derive the far-field, i.e., Debye, approximation of our formulas. The solution shows that when the paraboloid is infinite, its focusing properties exhibit a dispersive behavior; that is, the structure of the field distribution in the vicinity of the focus strongly depends on the wavelength of the illumination. We show that for an infinite paraboloid the confinement of the focused energy worsens, with the energy distribution spreading in the focal plane. 2000 Optical Society of America [S0740-3232(00)01309-0] OCIS codes: 260.0260, 260.2110, 050.1960, 260.5430.
66 citations
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TL;DR: A novel high-resolution stage scanning confocal microscope for fluorescence microscopy and spatially resolved spectroscopy with a high numerical aperture (NA 1) parabolic mirror objective is investigated and a spatial resolution close to the diffraction limit is achieved.
Abstract: A novel high-resolution stage scanning confocal microscope for fluorescence microscopy and spatially resolved spectroscopy with a high numerical aperture (NA≈1) parabolic mirror objective is investigated. A spatial resolution close to the diffraction limit is achieved. As microscopic fluorescent test objects, dye-loaded zeolite microcrystals (diameter approx. 0.4 µm) and single fluorescent molecules were used. Confocal fluorescence images show a spatial resolution of Δx=0.8·λ both at room temperature and at 1.8 K. Imaging of a quasi-point light source and focusing by the parabolic mirror were investigated experimentally and theoretically. Deviations between the theoretical results for a perfect parabolic mirror and the experimental results can be attributed to small deviations of the mirror profile from an ideal parabola.
65 citations
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65 citations
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TL;DR: In this paper, the authors describe a recently realized experiment producing the most spherical cavitation bubbles today, where the bubbles grow inside a liquid from a point plasma generated by a nanosecond laser pulse.
Abstract: We describe a recently realized experiment producing the most spherical cavitation bubbles today. The bubbles grow inside a liquid from a point plasma generated by a nanosecond laser pulse. Unlike in previous studies, the laser is focussed by a parabolic mirror, resulting in a plasma of unprecedented symmetry. The ensuing bubbles are sufficiently spherical that the hydrostatic pressure gradient caused by gravity becomes the dominant source of asymmetry in the collapse and rebound of the cavitation bubbles. To avoid this natural source of asymmetry, the whole experiment is therefore performed in microgravity conditions (ESA, 53rd and 56th parabolic flight campaign). Cavitation bubbles were observed in microgravity (∼0 g), where their collapse and rebound remain spherical, and in normal gravity (1 g) to hyper-gravity (1.8 g), where a gravity-driven jet appears. Here, we describe the experimental setup and technical results, and overview the science data. A selection of high-quality shadowgraphy movies and time-resolved pressure data is published online.
65 citations