Fresnel zone

About: Fresnel zone is a research topic. Over the lifetime, 2337 publications have been published within this topic receiving 37650 citations.

Computer simulation of Fresnel diffraction from double rectangular apertures in one and two dimensions using the iterative Fresnel integrals method

Abstract: We have applied the iterative Fresnel integrals method for the computation and simulation of the Fresnel diffraction images created by double apertures in one and two dimensions. Necessary formalism has been derived and the relevant computation algorithms have been developed for this application. The computer simulated images show an interesting combination of Fresnel diffraction images with mutual interference effects between the light diffracted from the two apertures. Transition to the expected Fraunhofer diffraction pattern for double apertures or slits is also observed by the simulations.

The efficiency of relief-phase diffractive elements at a small number of Fresnel zones

Abstract: A technique and investigation results are presented on the effect of the number of Fresnel zones on the diffraction efficiency and quality of the wave front formed by a diffractive optical element. Equations are presented for the microstructure reliefs of diffractive optical elements making (regardless of the number of Fresnel zones) the wavefront shape coinciding with the calculated one and ensuring 100% diffraction efficiency at a single wavelength and, in the case of two-layer structures, almost 100% diffraction efficiency in a wide spectral range.

Propagation characteristics in land mobile satellite systems

Abstract: A description is given of experiments on land mobile satellite systems carried out with the Engineering Test Satellite-V (ETS-V) at 1.6 and 1.5 GHz. Typical propagation characteristics observed, a received power distribution measured in a local area, and estimation methods for received signal variations caused by a building and a single tree are described. It is shown that the shadowing effects of a building can be estimated exactly from a knife-edge diffraction model. Single-tree attenuation can be estimated from the relation between the area of the first Fresnel zone and the area that the tree occupies in it. It is concluded that mobile satellite communication services are achievable on about 90% of the main road in the area including local cities in Japan. >

Towards stacked zone plates

Abstract: Fresnel zone plates are the key optical elements for soft and hard x-ray microscopy. For short exposure times and minimum radiation load of the specimen the diffraction efficiency of the zone plate objectives has to be maximized. As the efficiency strongly depends on the height of the diffracting zone structures the achievable aspect ratio of the nanostructures determines these limits. To reach aspect ratios ≥ 20:1 for high efficient optics we propose to superimpose zone plates on top of each other. With this multiplication approach the final aspect ratio is only limited by the number of stacked zone plate layers. For the stack process several nanostructuring process steps have to be developed and/or improved. Our results show for the first time two layers of zone plates stacked on top of each other.

Fresnel zone effects in the scattering of sound by cylinders of various lengths

Abstract: The backscattering behavior of straight cylinders is examined whose lengths range from much less than the diameter of the first Fresnel zone of the source/receiver pair to much greater than the first Fresnel zone, with special emphasis on the complicated ‘‘transitional region,’’ where the cylinders occupy a finite number of Fresnel zones (≊1–5). In general, the scattering characteristics of cylinders in this region can only be described numerically. The scattering is described by first adapting the deformed cylinder formulation [T. K. Stanton, J. Acoust. Soc. Am. 86, 691–705 (1989)] to the point‐source/point‐receiver combination. Numerically evaluating this expression showed the scattering characteristics to be dominated by Fresnel zone effects—oscillations in the backscatter versus length curve caused by constructive and destructive wave interferences due to phase shifts from contributions along the cylinder axis. An experiment was performed that involved measurement of backscatter versus cylinder length in the transitional region, and there is reasonable agreement between the results and the trend as predicted by the approximate theory.