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
Patent
11 Sep 2006
TL;DR: In this article, a zoned radiation device for converging radiation of a wavelength g to a focus at distance b is presented, where the device can focus the radiation with wavelength g at a distance b with an autocorrelation/point spread function that is sharper than the autocorerelation/Point spread function produced by zones configured to a Fresnel zone construction.
Abstract: A zoned radiation device for converging radiation of a wavelength g to a focus at distance b, the device comprising a first set of zones 14 and a second set of zones 15, wherein the first set of zones have a different characteristic to the second set and wherein the area of the zones decrease as their distance from a predetermined point increases, and one or more zone distances at which a zone of the first set with a first characteristic switches to a second zone with a second characteristic are configured such that the device can focus the radiation with wavelength g at a distance b with an autocorrelation/point spread function that is sharper than the autocorrelation/point spread function produced by zones configured to a Fresnel zone construction The device may be used as a coded aperture, a collimator, an ophthalmic lens or a teleconverter lens for a compact digital camera Also disclosed is a non-linear chirp signal for carrying, collecting or determining data

2 citations

Journal ArticleDOI
TL;DR: In this article, two techniques are described which remove this background by employing optical interference during the image reconstruction process, and the experimental results are presented for one of the techniques are compared to the other.

2 citations

Journal ArticleDOI
Hongwen Ren1, Ligong Zhang1, Li Xuan1, Ming Chen, Ximin Huang 
01 Jun 2001
TL;DR: In this paper, a light-focus device consisting of two glass substrates and one liquid crystal (LC) layer was fabricated and demonstrated, where each indium tin oxide electrode coated on the two inner substrate surfaces of the device was etched into Fresnel zone patterns.
Abstract: A novel light-focus device was fabricated and demonstrated. The device consists of two glass substrates and one liquid crystal (LC) layer. Each indium tin oxide electrode coated on the two inner substrate surfaces of the device was etched into Fresnel zone patterns. In field-off state, the transmission is uniform and light is not focused. In field-on state, a 2π phase difference between adjacent zones can be adjusted. Then the device becomes a Fresnel phase zone plate and acts as a lens. Moreover, for getting transmission independent of light polarization direction, the LC layer was treated by twist of 180° along the normal of substrate surfaces.

2 citations

Journal ArticleDOI
TL;DR: Adekola et al. as discussed by the authors presented an analysis of the Fresnel zone and diffraction fields near the boresight of a typical antenna, using a tapered parabolic source excitation.
Abstract: Based upon a generalized theory of an analytic model of a practical acoustic radar (echosonde) antenna [S. A. Adekola, J. Acoust. Soc. Am. 60, 230–239 (1976)] whose potential has been exploited to measure atmospheric turbulent velocity fields and temperature fluctuations, we present an analysis of the Fresnel zone and diffraction fields near the boresight of a typical antenna. Invoking the Fresnel zone approximation and employing a tapered parabolic source excitation, the Fresnel zone field at the antenna boresight is evaluated in closed forms in terms of a highly convergent Lommel series function of the form Ω0m (ν,n) that is expedient for practical computations. A generalized diffraction integral equation at the boresight region, which can be used for both circularly symmetric and asymmetric echosonde apertures, is formulated whereby the existing integral, previously derived in the reference above, is split into a sum of zeroth‐order Hankel and Lommel transforms that describe the field in the two princi...

2 citations

Journal ArticleDOI
TL;DR: In this paper, an experimental study in W band about the behavior of a plane Fresnel re∞ector when the feeder changes its position on the surface of a sphere whose centre is the same of the Fresnel plate zones is presented.
Abstract: This work presents an experimental study in W band about the behavior of a plane Fresnel re∞ector when the feeder changes its position on the surface of a sphere whose centre is the same of the Fresnel plate zones. For this purpose, an experimental system based on seven Fresnel plate zones and two difierent levels has been developed. The center frequency of the re∞ector is 96GHz, the focal length is 100mm and height between levels is 0.78mm. Based on this Fresnel re∞ector, an experimental set up has been developed. The horn antenna feeder is flxed and situated in far fleld and the receiver is also a horn antenna located at the Fresnel focal distance. Both the re∞ector and the receiving antenna have some rotation capability to enable measurements from difierent angles. The experimental results show a good, stable behavior in gain versus the angular position of the feeder. This special property of Fresnel re∞ectors is impossible in parabolic re∞ectors and consequently, Fresnel re∞ectors could be used in new applications as radar imaging, increasing the radar fleld of view or improving the resolution by means of several squint feeders working simultaneously on the same lens or re∞ector. Therefore, the main objective of this paper is to analyze the behavior of this experimental set up for developing new Fresnel re∞ector-based applications.

2 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