Fresnel zone

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

Fabrication of tungsten Fresnel zone plates for hard x-rays using wet etching

Abstract: A novel and scalable method to fabricate tungsten Fresnel zone plate (FZP) structures with a high aspect ratio using the wet etching method is presented. FZPs with an outermost zone width of 370 nm and a height of 1.1 μm were fabricated in tungsten on a 35 μm polyimide film. They were designed for a focal length of 50 cm at 8 keV such that the radius is 100 μm for 142 zones, with an opaque center zone. The fabrication method presented is a simple single step resist process. The testing of FZP was carried out at the Indus-2 synchrotron source, where focusing was observed as per design parameters. The transmission characteristics of polyimide coupled with the phase shifting properties of tungsten make the FZP useful also at lower energies. An improvement in the zone plate structural parameters and hence its performance has also been discussed.

Design of diffractive optical surfaces within the SMS design method

Abstract: The extension of the SMS method to design diffractive surfaces is presented. This method involves the simultaneous calculation of N/2 diffractive surfaces, using the phase-shift properties, such that N one-parameter wavefronts can be imaged

Alternative coverage analysis method reduces infill shooting

Abstract: Combined with steerable streamer technology, the use of Fresnel zone binning has reduced infill surveys to single-digit cost percentages.

Fresnel zone plate

Abstract: PURPOSE:To reduce an aberration in case a titled zone plate is used by a shorter wavelength than a wavelength used for a holography by recording an interference fringe by the holography on a curve surface which is curved symmetrically in its rotation. CONSTITUTION:In case a Fresnel zone plate is made by an interference on a plane plate P of two optical waves of luminous flux W1 and W2, it is the same as what is called a hologram of a point image, and if a wavelength is the same as a wavelength of a recording light source in case of condensing a light from a point O to I, the focal position is constant with regard to any annular zone, and a point image of non-aberration is obtained in a position of I. In case the Fresnel zone plate prepared in this way is used by other wavelength than a wavelength of a recording light source, a large aberration is generated and it does not become practical, therefore, the aberration is corrected by forming a hologram of a point image on the spherical surface. That is, in case a relative relation of the recording light source is constant, the aberration can be corrected by forming the zone plate to a spherical surface, therefore, the Fresnel zone is improved remarkably by forming it on a curved surface.

Diffraction of nonsinusoidal sound in the sea

Abstract: A theory of diffraction is applied to nonsinusoidal emissions of low‐frequency sound in the sea. The ray approximation is sometimes good and other times not so good. Some theories for the scattering of nonsinusoidal emission of sound assume that propagation occurs within a Fresnel zone of the ray path. This assumption is incorrect. Indeed, the use of a correctly sized region based on a theory of diffraction appears to be able to help resolve major discrepancies between observations and such theories for acoustic fluctuations. Indeed, the correctly sized region can be orders of magnitude smaller than given by a Fresnel radius.