Topic
Fresnel zone
About: Fresnel zone is a research topic. Over the lifetime, 2337 publications have been published within this topic receiving 37650 citations.
Papers published on a yearly basis
Papers
More filters
••
TL;DR: In this paper, a method for determining the boundary conditions for the radiance in the Fraunhofer zone through radiance of the incident radiation is proposed, which can be generalized to other problems of optics, thereby providing the possibility of using computationally efficient ray approximation-based methods to determine the light fields.
Abstract: The wavelength is that natural scale that determines the applicability domains of the ray approximation and
the wave approximation of light. If the change of the radiation power spatial density is significant at the
wavelength scale, we deal with the light diffraction phenomenon, which is a subject to the wave optics. Let
us consider the diffraction phenomenon at the diaphragm. It is possible to distinguish the near zone with
significant wave inhomogeneities (i.e. the Fresnel zone) and the far Fraunhofer diffraction zone, in which
the wave becomes close to homogeneous (the so-called quasi-homogeneous) and the ray approximation is
possible. The problem is that there is no explicit relationship between the radiance of the rays before and
after diaphragm. Method for determining the boundary conditions for the radiance in the Fraunhofer zone
through the radiance of the incident radiation is proposed in the paper. This approach for computing the
radiance field in the Fraunhofer zone can be generalized to other problems of optics, thereby providing the
possibility of using computationally efficient ray-approximation-based methods to determine the light fields.
3 citations
••
01 Jul 1998-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: In this article, a high precision alignment system was developed for online monitoring of the tracking detectors of HERMES, which consists of a He-Ne laser, Fresnel zone plates, CCD cameras, and electronics to read out the image.
Abstract: A high precision alignment system has been developed for online monitoring of the tracking detectors of HERMES. The system consists of a He–Ne laser, Fresnel zone plates, CCD cameras, and electronics to read out the image. It records the alignment information of each detector automatically every 30 min during the experiment. The relative detector positions can be monitored with a precision of better than ±60 μ m (1σ).
3 citations
••
TL;DR: In this paper, a micro-zone plate of 250 zones and 55 nm outermost ring width at the electron storage ring BESSY in Berlin was used for X-ray microscopy.
3 citations
••
TL;DR: In this paper, height gain curves indicate the presence of specular and diffuse multipath components, which are separated out using discrete fourier transform-based filtering technique and reflection coefficients are computed for various types of terrain covers.
Abstract: Measurements of height–gain interference patterns at 35 GHz are carried out in order to obtain multipath interference data over various types of terrain viz. grass, road surface and concrete. The antenna with a beam width of 21° is used both at transmitting and receiving ends to ensure full illumination of Fresnel zones. The transmitting antenna height is kept at 1 m and receiving antenna height is vertically translated from 1 through 4 m, with a horizontal range separation of 74 m. The polarisation combination is vertical transmit and vertical receive. The system geometry provides low-grazing angle incidence. The recorded height–gain curves indicate the presence of specular and diffuse multipath components. Specular and diffuse multipath components are separated out using discrete fourier transform-based filtering technique and reflection coefficients are computed for various types of terrain covers. The results can be vitally useful for millimetre wave radar, guidance, remote sensing and communication systems operating near the surface in arid conditions.
3 citations
••
TL;DR: In this paper, the exact calculation of the field at a point due to a single Fresnel zone is carried out by using the Maggi-Rubinowicz contour integral, and the result agrees with the Fresnel theorem in the limit for k very large, k being the propagation constant of the incident wave.
Abstract: The exact calculation of the field at a point due to a single Fresnel zone is carried out by using the Maggi–Rubinowicz contour integral. The result agrees with the Fresnel theorem in the limit for k very large, k being the propagation constant of the incident wave. The results obtained suggest a new interpretation of the physical meaning of the Maggi–Rubinowicz contour integral in diffraction theory as representing a contribution of elementary or Fresnel zones, in exactly the same manner that the Kirchhoff integral does when considered as an expression of Huygens’ principle.
3 citations