Fresnel zone

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

Seismic Reflection Principles: Basics

Abstract: Seismic reflection events are caused by the impedance contrasts at layer interfaces having a minimum width (Fresnel Zone). Seismic studies to represent reliably the subsurface geology, require quality data, which depend on signal-to-noise ratio and resolution, the latter being the ability to image thin geologic features separately. This calls for a seismic broad-bandwidth source consisting of both low and high frequencies that can improve resolution limits to layer thicknesses.

Fresnel zone imaging of Bloch-modes from a Hollow-Core Photonic Crystal Fiber Cladding

Abstract: A Fresnel zone imaging technique at the output of a short length of hollow core photonic crystal fiber allows the identification of the photonic crystal cladding Bloch-modes. The experimental results show excellent agreement with theory.

Application of the edge wave superposition method

Abstract: Numerical examples of high-frequency synthetic seismograms of body waves in a 2-D layered medium with complex interfaces (faults, wedges, curvilinear, corrugated) are presented. The wave field modeling algorithm combines the possibilities of the ray method and the edge wave superposition method. This approach preserves all advantages of the ray method and eliminates restrictions related to diffraction by boundary edges and to caustic effects in singular regions. The method does not require two-point ray tracing (source-to-receiver), and the position of the source, as well as the type of source, and the position of receivers can be chosen arbitrarily. The memory and the time required for synthetic seismogram computation are similar to ray synthetic seismograms. The computation of the volume of the medium (the Fresnel volume or Fresnel zones), which gives the essential contribution to the wave field, is included in the modeling program package. In the case of complicated irregular interface (or a layered medium with a regular ray field at the last interface), the method displays a high accuracy of wave field computation. Otherwise, the method can be considered a modification of the ray method with regularization by the superposition of edge waves.

Methods and apparatus for scanning microscopy using one or more fresnel zone plates

Abstract: Microscopy methods and apparatus in which one or more microfabricated optical elements (e.g., one or more Fresnel zone plates) operate as one or an array of objective lenses. A single object or a plurality of objects may be scanned in parallel. A single, low-numerical-aperture relay optic can be used with the one or more optical elements eliminating the need for one or more confocal pinhole apertures. When an array of optical elements is used, hundreds to thousands of objects can be imaged or inspected simultaneously onto a two-dimensional imaging device, such as a CCD array. The microfabricated optical elements can be readily configured for imaging with a solid immersion medium. Imaging resolutions on the order of one wavelength of the illumination source, and less, can be achieved.

Multilevel Fresnel zone lenses capable of being fabricated with only one binary mask

Abstract: Multi-level approximated Fresnel zone lenses with reduced level numbers in the outer zones are investigated and compared with Fresnel zone lenses of unique level numbers over the whole lens. Calculations of the fabrication error effects on diffraction efficiency for both lens types are performed. Measurements of focussing efficiency show that. especially for Gaussian beam illumination, segmented Fresnel zone lenses can reach nearly as high focussing efficiencies as normal Fresnel zone lenses. Arrays of segmented lenses can be fabricated using only one binary Fresnel zone lens mask with the aid of a modified optical stepper with fixed scaling down factors in the ratio of 1: 1/(root)2 from one to the next step of pattern transfer in the lithographic process. The fabrication of such lenses could be advantageous because the generation of precise e-beam written masks with a large number of binary ring zones is time consuming and expensive.