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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11 Oct 2010
TL;DR: In this paper, a variable focus lens system for eyeglasses is described, which consists of superimposed first and second thin lenses, simulating Alvarez lenses, with one side of each lens divided into Fresnel zones and zone boundaries.
Abstract: A variable focus lens system for eyeglasses is disclosed. The system consists of superimposed first and second thin lenses, simulating Alvarez lenses, with one side of each lens divided into Fresnel zones and zone boundaries. The second lens element is slidable for focus adjustment. The Fresnel zone boundary surfaces are made parallel to the user's optical line of sight to reduce visual obstructions, and the zone boundaries may be restricted to areas near the lens periphery to further reduce visual obstructions. The Fresnel zone boundaries may follow paths which enable equal, constant step size for the boundaries along their lengths. An opaque light absorbing coating may be applied to the zone boundaries to reduce light scattering. A fixed prescription lens, having the user's distance and astigmatism corrections, is superimposed on the first and second lens elements. In a second embodiment, a lens element may have at least one additional Fresnel lens component mated and bonded to it, forming a composite lens element. A composite lens element may have internal antireflection layers between the mated lenses, to further reduce internal reflections. The outer smooth sides of a lens element or composite lens element may have antireflection coating applied.
8 citations
TL;DR: This work develops numerical simulations by means of the Rayleigh-Sommerfeld approach, showing how roughness in both levels of the Fresnel zone plate affects the focalization of the lens.
Abstract: We analyze the focusing properties of Fresnel zone plates fabricated over steel tapes using laser ablation. Our intention is to implement the use of micro-optical elements when the use of conventional chrome-glass elements is not indicated. Because of the manufacture process, the surface presents a certain anisotropic roughness, which reduces the focusing properties. First, we develop numerical simulations by means of the Rayleigh-Sommerfeld approach, showing how roughness in both levels of the Fresnel zone plate affects the focalization of the lens. We also manufacture Fresnel zone plates over steel tape, and perform experimental verification that corroborates the numerical results.
8 citations
TL;DR: In this paper, the EarthStudy 360 Imager attenuated different types of wave characteristics considered as both random and coherent noise, in particular, different orders of multiples, and non-reflection seismic events such as Rayleigh, refraction, diffraction and side waves.
Abstract: The EarthStudy 360 Imager is an advanced depth imaging system that first maps the full recorded seismic data into the subsurface grid points and then decomposes the data into local angle domain (LAD) bins. It is based on specially designed diffraction operators using bottom-up ray tracing. In this article, we focus on the ability of the EarthStudy 360 Imager to attenuate different types of wave characteristics considered as both random and coherent noise – in particular, different orders of multiples, and non-reflection seismic events such as Rayleigh, refraction, diffraction and ‘side’ waves. The method is based on internal implementation of local slant stack (LSS) operators optimally designed for each primary ray pair associated with a given source-image point-receiver path and the corresponding seismic data event. The LSS is applied in the direction of the horizontal slowness components of the arriving rays at the acquisition surface, where the size of the LSS (the number of traces involved) is computed independently for each ray pair from its first Fresnel zone. Thus, primary reflection events sharing the same traveltime and the same surface directivity as the traced ray pairs are emphasized (highly weighted), while all other events (considered as noise) are simultaneously attenuated. We demonstrate our method in four different land data examples with different levels of geological complexities.
8 citations
TL;DR: In this article, the qualitative features of the lowest order mode profile of an unstable resonator can be predicted by a simple technique based on Fresnel zone theory, which is verified by experimentally measured mode profiles on an unstable cavity He-Xe laser.
Abstract: The qualitative features of the lowest order mode profile of an unstable resonator can be predicted by a simple technique based on Fresnel zone theory. The number of rings in the pattern and the occurrence of a local minimum or a local maximum on-axis can be predicted by computing the number of Fresnel zones subtended at the observation plane by the cavity aperture uniformly illuminated by a point source at the virtual focus. This technique has been verified by computer calculations of mode profiles both inside and external to the cavity for moderate Fresnel numbers. The results were also confirmed by experimentally measured mode profiles on an unstable cavity He-Xe laser. The predicted cyclic nature of the mode loss with cavity aperture diameter was also confirmed experimentally.
8 citations
10 Apr 2016
TL;DR: In this article, a Fresnel Zone Plate (FZPL) antenna working in the V band with half phase correction is reported, and a low cost and straightforward technological process is used to manufacture the dielectric lens using only one foam material whose the Dielectric constant is controlled.
Abstract: A Fresnel Zone Plate lens (FZPL) antenna working in V band is reported in this paper with half phase correction. A low cost and straightforward technological process is used to manufacture the dielectric lens using only one foam material whose the dielectric constant is controlled. Simulation and measurement results are in good agreement that confirms the viability of such a process to fabricate inhomogeneous structures. Good loss efficiency (73% at 60GHz) is obtained for this FZPL design.
8 citations