Fresnel zone

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

Comment on the “Corrected Fresnel Coefficients for Lossy Materials”

Abstract: It is shown that the “corrected” Fresnel reflection and transmission coefficients derived recently by Canning [1] using a complex transmission wave vector approach and involving a real true angle of refraction are identical to the traditional coefficients based on a complex angle of refraction.

Fresnel lens combination

Abstract: A focusing unit includes a Fresnel lens combination, where the Fresnel lenses are oriented to reduce shadowing losses. Shadowing is a scattering of light from reflection at the facet walls that separate adjacent Fresnel zones on a given Fresnel lens. Two substantially adjacent Fresnel lenses make up the focusing unit, which can be used as a condenser that collects light from a source in a projection system. Both Fresnel lenses have non-faceted sides that face the light source. The first Fresnel lens collimates the light from the source. The second Fresnel lens receives the collimated beam, with a range of incident angles determined by the spatial extent of the source. Components such as reflective polarizers and anti-reflection coatings can be used between the Fresnel lenses and can be applied to the non-faceted side of the second Fresnel lens.

Turbulent Lidar: I−Design

Abstract: Two designs of a laser radar system based on the backscatter amplification effect (BSA) are suggested. The system is a micropulse aerosol lidar with two receiving channels, one of which records an increase in the lidar returns at the laser beam axis as the atmospheric turbulence intensifies. The second channel does not respond to the BSA and is required for calibration. The BSA effect manifests itself in a narrow spatial region around the laser beam axis; so, the receiver aperture should be small enough and comparable with the Fresnel zone. The creation of the turbulent lidar became possible with the advent of compact diode-pumped micropulsed lasers with high pulse repetition rates. The lidar is intended for continuous long-term unattended operation. It is eye-safe. Two designs of the turbulent lidar based on an afocal Mersenne telescope (mirror collimator) are suggested. BSA-2 and BSA-3 turbulent lidars are described. An algorithm is suggested for retrieval of the structure parameter of optical turbulence C 2 from lidar data based on the Vorob’ev’s approximation for a statistically homogeneous turbulent medium.

Amplitude, Fresnel zone, and NMO velocity for PP and SS normal-incidence reflections

Abstract: Inspired by recent ray-theoretical developments, the theory of normal-incidence rays is generalized to accommodate P- and S-waves in layered isotropic and anisotropic media. The calculation of the three main factors contributing to the two-way amplitude — i.e., geometric spreading, phase shift from caustics, and accumulated reflection/transmission coefficients — is formulated as a recursive process in the upward direction of the normal-incidence rays. This step-by-step approach makes it possible to implement zero-offset amplitude modeling as an efficient one-way wavefront construction process. For the purpose of upward dynamic ray tracing, the one-way eigensolution matrix is introduced, having as minors the paraxial ray-tracing matrices for the wavefronts of two hypothetical waves, referred to by Hubral as the normal-incidence point (NIP) wave and the normal wave. Dynamic ray tracing expressed in terms of the one-way eigensolution matrix has two advantages: The formulas for geometric spreading, phase shif...