scispace - formally typeset
Search or ask a question
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
More filters
Proceedings ArticleDOI
08 Oct 2018
TL;DR: This work proposes a diffraction-based sensing model to investigate how to effectively sense human respiration in FFZ, and deploys the system using COTS Wi-Fi devices to observe that the respiration sensing results match the theoretical model well.
Abstract: Recent work has revealed the sensing theory of human respiration outside the First Fresnel Zone (FFZ) using commodity Wi-Fi devices. However, there is still no theoretical model to guide human respiration detection when the subject locates in the FFZ. In our work [10], we propose a diffraction-based sensing model to investigate how to effectively sense human respiration in FFZ. We present this demo system to show human respiration sensing performance varies based on different human locations and postures. By deploying the respiration detection system using COTS Wi-Fi devices, we can observe that the respiration sensing results match the theoretical model well.

22 citations

Journal ArticleDOI
TL;DR: In this paper, the on-axis gain of a uniformly illuminated rectangular aperture is derived which is valid in the "Optical Fresnel Zone." This equation is formulated in terms of the ordinary radiation field gain multiplied by a correction factor which depends upon the aperture dimensions and the distance, R, from the aperture at which the gain is measured.
Abstract: An equation for the on-axis gain of a uniformly illuminated rectangular aperture is derived which is valid in the "Optical Fresnel Zone." This equation is formulated in terms of the ordinary radiation field gain multiplied by a correction factor which depends upon the aperture dimensions and the distance, R, from the aperture at which the gain is measured. A table of the function [C2(v)+S(v)]/v2 is given; C(v) and S(v) being the Fresnel integrals. The gain of a square aperture (LXL meters) in the Fresnel-zone region is compared with the gain of a circular aperture and it is shown that for apertures of equal Gsquare < Gcircle when (L2/?)

22 citations

Journal ArticleDOI
TL;DR: It is found that random errors significantly decrease the contrast transfer of X-ray microscopes and an upper bound for the mean acceptable variance of the deposition rate is derived.
Abstract: Fresnel zone plates produced by electron beam lithography and planar etching techniques provide a resolving power of about 10 nm. An alternative zone plate fabrication approach is based on alternately coating a micro-wire with two different materials. With this process, very thin zone layers with very high aspect ratios can be deposited. However, depending on the fabrication method, random zone positioning errors may introduce strong aberrations. We simulate the effect of positioning errors using different random fluctuations and study their influence on zone plate resolution. We find that random errors significantly decrease the contrast transfer of X-ray microscopes. Additionally, we derive an upper bound for the mean acceptable variance of the deposition rate.

22 citations

Journal ArticleDOI
28 Nov 2018-Nature
TL;DR: In this article, a gas jet with a density gradient across the profile of the extreme-ultraviolet beam is used to produce a gas-phase prism that leads to a frequency-dependent deflection of the beam.
Abstract: Refraction is a well-known optical phenomenon that alters the direction of light waves propagating through matter. Microscopes, lenses and prisms based on refraction are indispensable tools for controlling light beams at visible, infrared, ultraviolet and X-ray wavelengths1. In the past few decades, a range of extreme-ultraviolet and soft-X-ray sources has been developed in laboratory environments2–4 and at large-scale facilities5,6. But the strong absorption of extreme-ultraviolet radiation in matter hinders the development of refractive lenses and prisms in this spectral region, for which reflective mirrors and diffractive Fresnel zone plates7 are instead used for focusing. Here we demonstrate control over the refraction of extreme-ultraviolet radiation by using a gas jet with a density gradient across the profile of the extreme-ultraviolet beam. We produce a gas-phase prism that leads to a frequency-dependent deflection of the beam. The strong deflection near to atomic resonances is further used to develop a deformable refractive lens for extreme-ultraviolet radiation, with low absorption and a focal length that can be tuned by varying the gas pressure. Our results open up a route towards the transfer of refraction-based techniques, which are well established in other spectral regions, to the extreme-ultraviolet domain. A refractive lens and a refractive prism for extreme-ultraviolet radiation have been developed that use the deflection of the radiation in an inhomogeneous jet of atoms.

22 citations

Journal ArticleDOI
TL;DR: In this paper, the imaging properties of a convergent mirror were evaluated both before and after a multilayer reflective coating was applied to the mirror and it was found that the multi-layer coating had only a small effect on these scans.
Abstract: Circular Fresnel zone plates, apodized linear zone plates, and a variety of apertures have been fabricated in smooth germanium films deposited on boron doped silicon membranes. Zone widths as small as 60 nm have been fabricated in absorbing layers from 0.25 to 0.5 μm thick. These results were achieved using electron beam lithography in a trilevel resist followed by reactive ion etching to transfer the patterns. These optical elements are key components in a soft x‐ray ‘‘focalometer’’ currently being tested at the NSLS at Brookhaven National Laboratories. The focalometer is a system which can be used to determine the imaging properties of an optical element. In this work it has been used to evaluate the imaging properties of a convergent mirror both before and after a multilayer reflective coating was applied. Results of knife edge scans of images formed by a spherical mirror using 14 nm radiation are reported. The multilayer coating applied to the mirror is found to have only a small effect on these scans.

22 citations


Network Information
Related Topics (5)
Resonator
76.5K papers, 1M citations
83% related
Wave propagation
55K papers, 1.1M citations
82% related
Polarization (waves)
65.3K papers, 984.7K citations
82% related
Optical fiber
167K papers, 1.8M citations
81% related
Diffraction
63.7K papers, 1M citations
79% related
Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202326
202249
202137
202052
201965
201878