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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07 May 1990
TL;DR: In this article, the far-field antenna pattern of phase-correcting Fresnel zone plates is analyzed, based primarily on work done in the optical regime, and measured characteristics of zone-plates in the microwave-millimeter-wave region are also presented.
Abstract: The far-field antenna pattern of phase-correcting Fresnel zone plates is analyzed, based primarily on work done in the optical regime. Measured characteristics of zone-plates in the microwave-millimeter-wave region are also presented. Since the zone plate accomplishes focusing through diffraction and interference, rather than refraction, the overall efficiency for collecting the radiation flux that passes through the aperture is an important consideration. This efficiency has been determined analytically to be approximately 40.5% for a phase-reversal plate and 81% for a quarter-period plate. Thus, the intensity at the focus, relative to that produced by a hyperboloidal lens, is 3.9 dB down or 0.9 dB down respectively, for the phase-reversal or quarter-period cases. Early investigations in the microwave-to-millimeter-wave range developed formulas for calculating the radii and depth of annular cuts, and measured the axial intensity variation near the focus and the antenna patterns at 10, 140, and 210 GHz. Measurements have been made of off-axis image intensity and image position errors at 140 GHz, and the results are excellent. >
8 citations
TL;DR: In this article, the authors present two important issues often demanded when patterning DOEs using EBL: the first one is the attainment of accurate resist three-dimensional shaping to increase DOE efficiency, this task is accomplished by developing a new proximity correction algorithm able to shape the resist in one shot of exposure.
8 citations
TL;DR: Zhang et al. as mentioned in this paper proposed a zoom liquid lens employing a multifocal Fresnel zone plate, which can realize zooming using only one tunable liquid-liquid interface, which is not available for conventional liquid lens.
Abstract: We propose a zoom liquid lens employing a multifocal Fresnel zone plate. The proposed lens has two optical surfaces: liquid-liquid interface and Fresnel zone plate. The Fresnel zone plate is designed to have a multifocal point and an increased depth of focus. Therefore, the proposed lens has two obvious advantages. Due to increased depth of focus, the proposed lens can realize zooming using only one tunable liquid-liquid interface, which is not available for conventional liquid lens. Thus, it is possible to remove conventional zooming mechanisms from cameras. Besides, the focal length tuning range is also increased, and a lens system based on the proposed lens can simultaneously collect two images with different magnifications. We present the design, fabrication and characterization of the proposed lens. The shortest positive and negative focal length are ∼17.5mm and ∼-34.5mm and the diameter is 5mm. The zoom ratio of the proposed lens reaches ∼1.48×. Our results confirm that the proposed lens has widespread applications in imaging system.
8 citations
TL;DR: In this article, the optical properties of micro-fabricated Fresnel zone plates (FZPs) were simulated as an alternative to spatial light modulators (SLMs) for producing non-trivial light potentials to trap atoms within a lensless Fresnel arrangement.
Abstract: We have simulated the optical properties of micro-fabricated Fresnel zone plates (FZPs) as an alternative to spatial light modulators (SLMs) for producing non-trivial light potentials to trap atoms within a lensless Fresnel arrangement. We show that binary (1-bit) FZPs with wavelength (1μm) spatial resolution consistently outperform kinoforms of spatial and phase resolution comparable to commercial SLMs in root mean square error comparisons, with FZP kinoforms demonstrating increasing improvement for complex target intensity distributions. Moreover, as sub-wavelength resolution microfabrication is possible, FZPs provide an exciting possibility for the creation of static cold-atom trapping potentials useful to atomtronics, interferometry, and the study of fundamental physics.
8 citations
TL;DR: In this paper, the authors developed an algorithm to calculate multi-phase Fresnel Volume finite-frequency rays, and then presented an inversion method to simultaneous invert for both velocity and reflector geometry by using these multi-phase Fresnel volume finite frequency rays.
Abstract: Traditional ray tomography methods based on the high frequency assumption are sometimes unable to obtain a high resolution tomographic picture due to a deficient coverage of ray paths in real applications, especially for low velocity anomalous regions. In contrast, finite-frequency ray theory is more suitable for handling real seismic propagation problems because the travel time depends not only on the velocity distribution along a central ray (or traditional geometric ray), but also on the velocity values within a region (referred to as the first Fresnel Volume) which incorporates the central ray. In this study, we develop an algorithm to calculate multi-phase Fresnel Volume finite-frequency rays, and then present an inversion method to simultaneous invert for both velocity and reflector geometry by using these multi-phase Fresnel Volume finite-frequency rays. Using synthetic data examples, we compare the reconstructions of the velocity field and the reflector orientation using the Fresnel Volume ray tomographic methods and the traditional ray tomography approach. Results show that the former is advantageous over the latter, especially when the ray density is relatively low. An additional benefit of the Fresnel Volume finite-frequency ray tomographic method is that it can start with a low frequency to capture the coarse velocity structure, thereby mitigating the local minimum trapping problem, and then be tuned to a high frequency for delineating the fine velocity structure.
8 citations