Fresnel zone


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Fresnel zone

[freznel′]
Etymology: Augustine J. Fresnel, French physicist, 1788-1827
the region nearest the face of an ultrasound transducer. It is characterized by a highly collimated beam with great variation in ultrasound intensity and is generally the area of best image resolution. Also called near field.

Fresnel zone

in ultrasonography, the area of the sound beam between the transducer and the focal zone in which complex diffraction patterns occur.
References in periodicals archive ?
For example, while in the classroom, I learned that communications signals experience propagation loss over water, but the training did not address the underlying Fresnel Zone concept (p.
Focus X-rays in this system must be carried out using diffractive optical X called Fresnel Zone Plate.
Even the best x-ray microscope lenses (concentric circles of metal known as Fresnel zone plates), can't focus x-rays with high efficiency, so to get an image means using such intense radiation that it more quickly damages biological specimens.
As the corresponding effect at the point of observation P is attributable to the central Fresnel zone at Q acting alone, there is no need to know the nature of this aniso-tropy and hence it follows that dU(P) = (i/[lambda])U(Q) exp (ikQP)/QP.
The tech rep responds, "That's good to know, but what about proper Fresnel Zone clearance?
This area, known as the Fresnel Zone, must be kept clear of all obstructions (see figure).
Although the deployment was Near-Line-of-Sight (nLoS), with a partially obstructed fresnel zone, radio and radar interference at and around the airport prevented wireless systems from reliably connecting.
An algorithm is presented for assembling tiles into a variable spaced grating, the one-dimensional analog of a Fresnel zone plate.