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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.


Papers
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Journal ArticleDOI
TL;DR: In this article, a procedure is proposed to profile the mirror surface needed to produce under coherent illumination, a pre-specified Fraunhofer amplitude distribution U(ξ, ψ).
Abstract: A procedure is proposed to profile the mirror surface needed to produce under coherent illumination, a pre-specified Fraunhofer amplitude distribution U(ξ, ψ). The unknown optical path function ϕ(x y) in the diffraction integral is reconstructed from its stationary points {(x i, y i)}. The points {(x i, y i)} correspond to locations where the first Fresnel zone distribution F(x, y) is an extremum. The reconstruction utilizes the equivalence of the method of stationary points and the method of Fresnel zones. In Fraunhofer diffraction, the F(x, y) has the functional distribution of the inverse Fourier transform of U(ξ, ψ). We consider only Hermitian U(ξ, ψ)'s because they are generated by real F(x, y) distributions. The ϕ(x, y) is deduced from the behaviour of its first derivatives, which are expressed as product series expansions of {(x i, y i)}. The path function ϕ(x, y) which describes all the possible paths taken by the light waves from the point source to the observation plane via the reflecti...

3 citations

Journal ArticleDOI
TL;DR: The susceptibility of radar search antennas to radio-frequency interference (RFI) is determined to a great extent by the minor lobe structure as mentioned in this paper, and the use of detailed, threedimensional patterns to predict RFI is not practical because the fine structure of the antenna pattern changes with frequency, range in the Fresnel zone, and site effects.
Abstract: The susceptibility of radar search antennas to radio-frequency interference (RFI) is determined to a great extent by the minor lobe structure. The use of detailed, three-dimensional patterns to predict RFI is not practical because the fine structure of the antenna pattern changes with frequency, range in the Fresnel zone, and site effects. Statistical gain studies have shown that the characteristics of individual antennas and the mutual gain characteristics of two Interfering antennas can be described with Gaussian curves. The statistical description Is Independent of in-band frequency variations and range changes (including Fresnel zone), but site effects cause small changes in the median gain.

3 citations

Patent
20 Aug 1987
TL;DR: In this paper, the alignment mark of a Fresnel zone target is formed in a predetermined semiconductor chip, which is formed by a scribing line, and the mask is aligned by forming the surface of the semiconductor chips disposed under the target.
Abstract: PURPOSE:To accurately align masks by forming the surface of a semiconductor chip disposed under a Fresnel zone target formed on the mask in a projection or a recess. CONSTITUTION:The alignment mark 33 of a Fresnel zone target is formed in a predetermined semiconductor chip 32 formed by a scribing line 31. Recess regions 34 and projection regins 35 are repeatedly formed at a pitch l, for example, of 5mum on the periphery of the mark 33. When the size l' from the surface A of the region 34 to the surface B of the region 35 becomes 1/4 lambda, where lambda is the wavelength of alignment light. Thus, since the light arrived at the surface f a semiconductor wafer 1 through the surface of the mask 2 and reflected on the surface does not partly coincide with the light reflected on the surface of the mask, they do not extremely strengthen nor weaken each other. Therefore, a difficulty of the erasure of the spot of the Fresnel zone target on the mask can be avoided.

3 citations

Patent
13 Sep 1963

3 citations

Proceedings ArticleDOI
09 Oct 2006
TL;DR: In this article, the authors present a review of interferometric testing methods for aspheric surfaces based on computer-generated holograms (CGHs) and give a detailed discussion of limiting factors and critical issues.
Abstract: Absolute interferometric testing methods for aspheric surfaces based on computer-generated holograms (CGHs) are reviewed. Limiting factors and critical issues such as parasitic diffraction orders and the setup alignment are discussed and measurement results are given.

3 citations


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