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The relationship between the first Fresnel zone and the normalized geometrical spreading factor 1
Author(s) -
Sun Jianguo
Publication year - 1996
Publication title -
geophysical prospecting
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.735
H-Index - 79
eISSN - 1365-2478
pISSN - 0016-8025
DOI - 10.1111/j.1365-2478.1996.tb00153.x
Subject(s) - fresnel zone , fresnel number , fresnel diffraction , fresnel integral , fresnel equations , fresnel zone antenna , paraxial approximation , optics , zone plate , diffraction , reflection (computer programming) , geometrical optics , point (geometry) , enhanced data rates for gsm evolution , geometry , physics , geology , refractive index , mathematics , telecommunications , beam (structure) , smart antenna , dipole antenna , computer science , antenna (radio) , programming language
Conventionally, the Fresnel zone and the geometrical spreading factor are investigated separately, because they belong to different theories of wave propagation. However, if the paraxial ray method is used for establishing the Fresnel–Kirchhoff diffraction formula for a laterally inhomogeneous multilayered medium, it can be shown that the normalized geometrical spreading factor is inversely proportional to the area of the first Fresnel zone associated with the reflection point. Therefore, if no diffracting edge cuts the first Fresnel zone, the geometrical optics approximation represents the principal part of the wavefield obtained by Fresnel–Kirchhoff diffraction theory. Otherwise, the geometrical optics approximation has to be corrected by adding edge diffractions. It is also shown that Kirchhoff‐type migration and geometrical spreading factor correction both reduce the first Fresnel zone to a zone with unit area.