Topic
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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TL;DR: Any two-surfaced optical system, either refracting or reflecting, can be made stigmatic (aplanatic and anastigmatic) for object at infinity by using curved Fresnel surfaces instead of the usual conics.
Abstract: Any two-surfaced optical system, either refracting or reflecting, can be made stigmatic (aplanatic and anastigmatic) for object at infinity by using curved Fresnel surfaces instead of the usual conics. Such systems will also have a flat field under certain conditions and may even be distortion free. It is also shown that systems of flat Fresnel mirrors have incurable line coma.
3 citations
01 Jan 2007
TL;DR: In this article, a reflective diffraction optical elements (DOE) was developed for focusing radiation of terahertz free electron lasers (FEL) for studying condense matter non-uniformities and deformations.
Abstract: We have developed reflective diffraction optical elements (DOE) for focusing radiation of terahertz free electron lasers (FEL). Metal-dielectric Fresnel zone plates and metallic kinoform “lenses” were fabricated and tested using FEL radiation. A microbolometer camera (see the paper by Esaev et al. at this conference) sensitive to THz radiation had been applied for recording both terahertz beam caustic and terahertz images. Diffraction efficiency of a kinoform lens appears to be about unity. Quality of images obtained with the kinoform lens was studied. The lens was used as a key element for a Toepler optical system, which were used for studying condense matter non-uniformities and deformations. The experiments were performed at Novosibirsk and KAERI FELs.
3 citations
TL;DR: In this paper, a modified Fresnel zone plate reflector for broadband operation is presented, where a new technology based on slight deformations on a flat metallic surface is applied to obtain the geometrical model of the proposed flat reflector antenna.
Abstract: This work presents the design and analysis of a modified Fresnel zone plate reflector for broadband operation. A new technology based on slight deformations on a flat metallic surface is applied to obtain the geometrical model of the proposed flat reflector antenna. In comparison with reflectarrays, Fresnel zone reflectors are lossless, low cost, easy to fabricate and broadband. According to the specifications of a previously published reflectarray, a centre-fed prototype whose dimensions are 28 × 21 cm has been designed and analysed showing a maximum gain of 28.06 dBi at 12.5 GHz and a 32.8% 3 dB gain bandwidth in the range between 10.4 and 14.5 GHz. A second prototype has been designed and analysed to evaluate the performance of the proposed design method compared with a previous design of a Fresnel zone reflector. Better results in terms of gain and antenna efficiency have been obtained.
3 citations
22 Jun 2003
TL;DR: In this paper, a new class of diffractive optical element called a photon sieve, which consists of a great number of pinholes whose positions and radii are properly chosen, was developed for the focusing and imaging of soft X-rays.
Abstract: Recently, a new class of diffractive optical element called a photon sieve, which consists of a great number of pinholes whose positions and radii are properly chosen, was developed for the focusing and imaging of soft X-rays. In the initial work, the concept of Fresnel zone and the numerical calculation of Fresnel-Kirchhoff diffraction integral was used for the analysis and design. More recently, we developed the paraxially individual far-field model for the focusing analysis of low-numerical-aperture (low-NA) photon sieves. Here, we extend this model to the nonparaxial case of high-NA photon sieves working in the soft X-ray region, for which the paraxial Fresnel diffraction formula is invalid.
3 citations
29 Aug 1977
TL;DR: The separation of the focused + 1st order ofdiffraction picture from the zeroth and -1st order patterns is discussed in this paper, where the authors put up therelation between temperature and density in the emitting regions and the energy density distributions in the corresponding pictures, including the effect of chromatic aberration.
Abstract: Photographs of coronal active regions,taken with Fresnel Zone plates were quantitative-ly analyzed. For this purpose the properties of absorption edge filters used for wave-length selection and of film sensitivity, as well as the imaging properties of FresnelZone plates were comprehensively investigated.The separation of the focused +1st order ofdiffraction picture from the zeroth and -1st order patterns is discussed. We put up therelation between temperature and density in the emitting regions and the energy densitydistributions in the corresponding pictures, including the effect of chromatic aberration.An iteration procedure was applied to solve the set of equations,which characterizes thisrelation, leading to two dimensional maps of temperature and emission measure as illustra-ted for one active region.IntroductionX -ray photography is an essential tool to investigate the solar corona because of thehigh spatial resolution achievable with imaging systems. e u n of a few arc secshas been reached with grazing incidence mirror
3 citations