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Fresnel zone

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


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Patent
28 Nov 2012
TL;DR: In this article, a method for manufacturing an electrically-controlled zooming oriented polymer dispersed liquid crystal lens has been proposed, which has the excellent qualities of no motion component, low control voltage, low power consumption, short response time, high transmittance, correct focusing and easy miniaturization.
Abstract: The invention discloses a novel method for manufacturing an electrically-controlled zooming oriented polymer dispersed liquid crystal lens. The method comprises the following steps of: firstly, uniformly coating one layer of photoresist on a glass substrate plated with a transparent conductive film by using a rotary coating method; secondly, exposing, developing and etching the photoresist, manufacturing a cavity, pouring with an orientated polymer dispersed liquid crystal pre-polymerized mixture and obtaining a liquid crystal box after orientation of electric field and photopolymerization curing. Electrodes at the specific addresses on a glass substrate of the liquid crystal box are chosen and jointed into a Fresnel zone plate, the voltage is applied, and the liquid crystal director in the oriented polymer dispersed liquid crystal changes under the action of the applied electric field, so that the liquid crystal box is distributed along the Fresnel zone plate; the liquid crystal box has the effect of a lens after diffraction; the chosen electrodes are changed by using an electrode address control circuit according to the address requirements and jointed into new Fresnel zone plates with different focal lengths, and the voltage is applied, so that the purpose of subdividing the focal length and correctly and continuously varying the focal length is achieved. The novel method for manufacturing an electrically-controlled zooming oriented polymer dispersed liquid crystal lens has the excellent qualities of no motion component, low control voltage, low power consumption, short response time, high transmittance, correct focusing and easy miniaturization and has wide application prospects in a zoom optical imaging system, a video detecting and monitoring image pick-up system, an optical storage, an optical head of a DVD (Digital Video Disk) machine, and optical communication.
Journal ArticleDOI
28 Apr 2023
TL;DR: In this article , the authors considered the problem of approximate wave field in the so-called near, middle and far zones of observation, and showed that the positions of intensity maxima in the near zone of observation are determined by a cubic equation.
Abstract: The paper considers the problem of an approximate wave field in the so-called near, middle and far zones of observation. The possibility of introducing a more accurate than the Fresnel approximation, the so-called quasi-exact approximation, is indicated. For the interference problem usually considered in the Fresnel approximation, the intensity distribution in the near field of observation is obtained. It is shown that the positions of intensity maxima in the near zone of observation are determined by a cubic equation.
Journal ArticleDOI
TL;DR: In this article , the results of an experimental verification of the previously proposed all-optical wavelength-selective multichannel switch based on an off-axis Fresnel zone plate in the millimeter wavelength range without the use of micromechanical devices or non-linear materials are presented.
Abstract: The results of an experimental verification of the concept of the previously proposed all-optical wavelength-selective multichannel switch based on an off-axis Fresnel zone plate in the millimeter wavelength range without the use of micromechanical devices or non-linear materials are presented. A laboratory prototype of such a device is considered and its main parameters are discussed. It is shown that the optical isolation of switched channels for a switch based on an off-axis zone plate can reach 15 dB at a frequency difference of 25 GHz in the frequency range of 93–136 GHz.
Journal ArticleDOI
TL;DR: In this paper , the principles, state of the art and problems of diffractive optics used to focus X-ray and γ-radiation in telescopes at orbital stations are discussed.
Abstract: The review is devoted to the principles, state of the art and problems of diffractive optics used to focus X-ray and γ-radiation in telescopes at orbital stations. Various multilayer structures for normal incidence telescopes, supermirrors for Wolter optics, Laue lens as a soft γ-radiation concentrator, as well as modified Fresnel zone plates for focusing radiation in a wide energy range with an unprecedented high angular resolution (10-1-10-3''). Keywords: X-ray and γ-radiation, X-ray and γ-telescopes, diffraction, multilayer structures, Laue lens, Fresnel zone plates.
DissertationDOI
20 Feb 2022
TL;DR: In this paper , a dedicated synchrotron endstation for waveguide-based holographic imaging was designed and built based on the results of these conceptual experiments, along with the specifications and properties of the Kirkpatrick-Baez focussing mirrors and other mechanical and optical components.
Abstract: X-ray microscopy has emerged as a powerful and versatile imaging technique in many fields of science over the last years, offering insights in opaque media at high spatial resolution. A major challenge remains the fabrication of suitable X-ray lenses, e.g., Fresnel zone plates or compound refractive lenses. In an alternative approach of a lensless imaging scheme the sample is illuminated by a coherent X-ray beam. The sample information is then reconstructed from the recorded diffraction signal by numerical iterative algorithms. Within this thesis the basics of lensless holographic imaging with X-Ray waveguides are summarised and extended to the concept of waveguide-based X-ray interferometry. The specific instrumentation required for the conceptual experiments of waveguide-based holographic imaging is explained and illustrated by the obtained results. Based on the results of these conceptual experiments a dedicated synchrotron endstation for waveguide-based holographic imaging was designed and built. The specifications and properties of the Kirkpatrick-Baez focussing mirrors and other mechanical and optical components are described in detail, along with the instrument control system and various available detectors. First commissioning results prove the imaging abilities of the presented endstation.

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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202326
202249
202137
202052
201965
201878