Fresnel zone

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

Three Fresnel Zone Examples

Abstract: Three case histories demonstrate the significance of the Fresnel zone, and the importance of 3-D seismic In the first example, an operator attempted to acquire 2-D seismic data to determine whether a producing reservoir on an adjacent property covered sufficient area on his property to warrant a well Analysis of the Fresnel zones, unmigrated and migrated, illustrate the ambiguity of seismic data In the second example, a well tested the middle of an AVO anomaly on a seismic line, but found no sand A 3-D survey shows the effect of the Fresnel zone and how the well missed the reservoir In the third example, a well tested an AVO anomaly present on four 2-D seismic lines, but logs showed nothing that would explain the seismic amplitude An offset well found the sand, again demonstrating the importance of the Fresnel zone in areas of rapid stratigraphic change

Manipulating antenna radiation patterns with angle holography

Abstract: We introduce a new method of integrating holography into microwave antennas. Interference patterns of a reference wave with a desired wave can be represented using tilted radiating elements. By either feeding the elements directly or with an incident wave excitation, the Angle Holography array can then reproduce the desired output wave. The proposed design aims to provide features current holographic systems do not posses such as frequency scalability, simplicity in feeding, and ease of design and fabrication. Two 1D array designs are discussed, one for beam steering and the other for Fresnel zone focusing. Through full wave simulations, preliminary results validate the proposed idea and designs.

Application of Phase-Reversal Fresnel Zone Plates for Improving The Elevation Resolution in Ultrasonic Testing with Phased Arrays.

Abstract: Currently, phased arrays have found wide application in ultrasonic nondestructive testing. Volumetric results provided by the inspections with linear phased arrays have low lateral resolution in the elevation direction of such probes. This fact complicates the defects characterization task. In this paper, we suggest the application of the Phase-Reversal Fresnel Zone Plate to increase the resolution of volumetric imaging with linear phased arrays. Application of such plates is aimed at ultrasonic focusing in the elevation plane whereas focusing on the active aperture plane is provided by the application of the Sampling Phased Array. Furthermore, the use of the Phase-Reversal Fresnel Zone Plate is advantageous due to the capability of its 3D printing and introduction to the existing automated testing systems avoiding making changes to the current software and hardware. The effectiveness of the plates was verified experimentally on the existing automated testing system. The obtained experimental results demonstrate that the application of the Phase-Reversal Fresnel Zone Plate allowed achieving the results of the higher resolution as well as improving the signal to noise ratio.

Material optimization for hard x-ray Fresnel zone plates

Abstract: Fresnel zone plates have recently been used as the focusing optic for hard x-ray (5 - 11 keV) microscopy techniques. Fresnel zone plates used in the hard x-ray regime focus by constructive interference effects based on the phase modulation of the incident x-ray beam and have experimentally been shown to focus 20 - 30% of the incident photons to less than a one- micron focal spot. The materials of choice for these zone plates have been Al, Cu, Ni, and Au. The focus of this work is the theoretical optimization of the focusing efficiency of phase- modulating Fresnel zone plates in the hard x-ray regime by appropriate material selection. The optimal materials for three different energy ranges will be examined (1 - 5 keV, 5 - 20 keV, and > 20 keV) and a discussion of the selection criteria involved will be presented.

Fabrication of high-resolution Fresnel zone plates by a single layer resist process

Abstract: In this work, fabrication of a high-resolution Fresnel zone plate (ZP) by a single layer electron beam (EB) resist process combined with a gold electroplating process is described. The ZP designed has a diameter of 80 µm and is composed of 250 rings (499 zones) of which the width of the outermost ring is nominally 40 nm. In order to fabricate a 150-nm-thick gold layer which acts as a phase-shifter for X-rays, a 200-nm-thick polymethylmethacrylate (PMMA) is used as a single layer resist. A 50 kV EB lithography system with a probe diameter of 3 nm is employed for high-resolution patterning. To prevent resist patterns with an aspect ratio of 5 from collapsing, we reinforce the ZP patterns by combining neighboring rings with ribs. It is demonstrated that a modified ZP pattern with a 40-nm-wide outermost ring which will not collapse can be fabricated whereas the original ZP pattern collapses at a high aspect ratio. Although control of the width of the gold phase shifter should be improved, the outermost ring with the nominal width of 40 nm can be electroplated.