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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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Patent
29 Apr 2015
TL;DR: In this article, a near-surface tomographic velocity analysis method based on the Fresnel zone is proposed, which has the advantages of the physical geography significance, the stability is strong, the efficiency is high, and calculation results are more real and reliable.
Abstract: The invention discloses a near-surface tomographic velocity analysis method. The near-surface tomographic velocity analysis method comprises the following steps: picking up travel time of first arrival by aiming at pre-stack data, and obtaining an initial model reflecting underground medium velocity distribution by pre-stack processing; performing a shortest path ray tracing method on the model to obtain simulated travel time; performing wave field simulation on the model by utilizing a frequency domain wave equation to obtain a sensitive kernel function reflecting disturbance of a medium to the travel time; establishing a corresponding inversion equation and solving to obtain a slowness updating amount. According to the tomographic velocity analysis based on the Fresnel zone, the problem that the solution of a large-scale sparse matrix is instable during the traditional temographic velocity analysis based on the ray theory is solved, and the seismic wave propagation rule is more truly portrayed; the near-surface tomographic velocity analysis method has the advantages that the physical geography significance is obvious, the stability is strong, the efficiency is high, and calculation results are more real and reliable.

9 citations

Journal ArticleDOI
TL;DR: In this paper, the lateral shift of Fresnel images is explained and derived for a one-dimensional amplitude grating of arbitrary transmittance profile, where the amplitude is defined as the amplitude of the image.
Abstract: The lateral shift of Fresnel images is explained. Derivations are presented for a one-dimensional amplitude grating of arbitrary transmittance profile.

9 citations

Journal ArticleDOI
TL;DR: In this paper, the irradiance covariance and variance functions associated with a reflected Gaussian-beam wave from a glint target (retroreflector) are calculated and compared with similar results based on a specular target (smooth finite mirror).
Abstract: The irradiance (intensity) covariance and variance functions associated with a reflected Gaussian-beam wave from a glint target (retroreflector) are calculated and compared with similar results based on a specular target (smooth finite mirror). Detailed results are presented for the normalized irradiance variance, or scintillation index, of the reflected wave for both types of reflector in an improved model of atmospheric turbulence that incorporates a high-wave-number rise just before the dissipation range in addition to inner–outer-scale parameters. Numerical comparisons show that values of the normalized irradiance variance based on the improved model of refractive-index fluctuations (henceforth called the modified spectrum) can be up to 32% greater than those predicted by the Kolmogorov power-law spectrum when the inner scale is comparable in size with the first Fresnel zone. All analytic expressions derived here are based on weak-fluctuation theory using generalized spectral representations of the complex phase perturbations.

9 citations

Journal ArticleDOI
TL;DR: In this paper, the authors applied the iterative Fresnel integrals method for the numerical computation of Fresnel diffraction patterns from rectangular apertures tilted at an arbitrary angle to the optical axis.
Abstract: We applied the iterative Fresnel integrals method for the numerical computation of Fresnel diffraction patterns from rectangular apertures tilted at an arbitrary angle to the optical axis. Detailed theoretical formalism is developed and discussed, and then is applied for the numerical computation and simulation of the actual diffraction patterns for an arbitrary optical configuration. The generated intensity distributions (images) show distortion and stretching in the direction of the tilt, but not in the other orthogonal direction. Significant decrease of the intensity is also predicted and observed, the decrease being proportionate with the tilt angle. The simulated images qualitatively resemble those published in the literature. In addition to single-axis tilts, simultaneous rotations (tilts) of the aperture in two orthogonal coordinate axes were also briefly considered and simulated.

9 citations

01 Sep 2003
TL;DR: In this paper, the authors present experimental results and analysis on the application of a new variable in the design of zone plate antennas, which is the choice of phase reference used in the definition of the Fresnel zones from which zone plates are constructed.
Abstract: I present experimental results and analysis on the application of a new variable in the design of zone plate antennas. This variable is the choice of phase reference used in the definition of the Fresnel zones from which zone plates are constructed. The standard zone plate construction assumes a specific choice for this reference phase which, however, can be chosen to have any value between 0 o and 360 o . When the reference phase is varied, antenna pattern measurements reveal small systematic changes in the main lobe gain accompanied by large improvements in the overall sidelobe level and position in both the E- and H-planes. Measurements also show that through variation of the reference phase, the phase of the main lobe can be varied controllably through 360 o . I conclude that reference phase is a useful new tool available to

9 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202326
202249
202137
202052
201965
201878