Fresnel zone

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

Microstructures for high‐energy x‐ray and particle imaging applications

Abstract: Coded imaging techniques using thick, micro‐Fresnel zone plates as coded apertures have been used to image x‐ray emission (2–20 keV) and 35 MeV Alpha particle emissions from laser driven micro‐implosions Image resolution in these experiments was 3–8 μm Extension of this coded imaging capability to higher energy x rays (∠100 KeV) and more penetrating charged particles (eg, ∠15 MeV protons) requires the fabrication of very thick (50–200 μm), high aspect ratio (10:1), gold Fresnel zone plates with narrow linewidths (5–25 μm) for use as coded apertures A reactive ion etch technique in oxygen has been used to produce thick zone plate patterns in polymer films The polymer patterns serve as electroplating molds for the subsequent fabrication of the free‐standing gold zone plate structures

System and method for analysis of seismic images

Abstract: A method for modeling illumination in a seismic survey of a subsurface region using a velocity model thereof includes specifying locations for a plurality of seismic shots, specifying locations for a plurality of seismic receivers, specifying a source radiation pattern for each source, tracing each ray from a reflection surface, computing an energy value for each ray using a Fresnel zone defined at a receiving surface and defined for a single frequency, and repeating the tracing and computing for each shot.

The resolution possible in imaging with diffracted seismic waves1

Abstract: The determination of the vertical and lateral extent of discontinuities is an important aspect of interpreting seismic reflection data. The Common Fault Point (CFP) stacking method appears to be promising in imaging discontinuities in acoustic impedance by making use of diffracted energy from a spatial array of receivers. The problems of vertical and lateral resolution in the method are most important when carrying out an interpretation. Source signature, subsurface velocities and the depth of the discontinuity are the most important parameters affecting the resolution. We use, for a perfectly coherent source, the first derivative of the Gaussian function which is an antisymmetric band‐limited wavelet. Rayleigh's, Ricker's and Widess' criteria are also applicable to this wavelet. The limits of vertical and lateral resolution are illustrated by using a step fault and a dike model respectively. The vertical resolution of the CFP method is found to be of the order of λ/16 which is half the theoretically predicted value for a single receiver. The lateral resolution is still limited by the size of the Fresnel zone which depends upon the velocity, two‐way time and the dominant frequency of the wavelet. The resolution limits of the CFP method are compared with that of the CDP method, prestack migration and post‐stack migration. Obtaining high resolution with real data is limited by the extent to which it is possible to generate a coherent source or to simulate one during computer processing with before stack seismic data. The CFP method is an artificial intelligence approach to imaging diffracting points as it localizes parts of the structure that scatter acoustic waves.

First Fresnel zone analysis in vehicle-to-vehicle communications

Abstract: The Fresnel zone is often utilized for the determination of the existence of the line-of-sight (LOS) in wireless communication links. In this paper, the first Fresnel zone clearance is analyzed especially focused on vehicle-to-vehicle (V2V) scenarios. The results reveal that clear wireless communication links with transmitter and receiver separation distances exceeding 500 m are regarded as non-LOS (NLOS) links.