Showing papers on "Fresnel zone published in 1971"
TL;DR: In the case of a periodic object, the wave amplitude in every point of a Fresnel diffraction pattern can be obtained from the values of the wave wave amplitude at a finite number of points in the object.
Abstract: In the case of a periodic object, the wave amplitude in every point of a Fresnel diffraction pattern may be obtained from the values of the wave amplitude at a finite number of points in the object...
99 citations
TL;DR: In this paper, an analytical expression for the irradiance pattern, in both the far field and near field, associated with the field propagating from an aperture with a truncated-gaussian field distribution was obtained by evaluating the diffraction integral subject to the Fresnel approximation.
Abstract: In this paper we obtain an analytical expression for the irradiance pattern, in both the far field and near field, associated with the field propagating from an aperture with a truncated-gaussian field distribution. This is accomplished by evaluating the diffraction integral subject to the Fresnel approximation. Numerical results are presented, which indicate how the patterns vary as the width of the truncated-gaussian field distribution changes.
78 citations
01 Jan 1971
TL;DR: The design and construction criteria for the implementation of an underwater viewing system based on holographic principles are emphasized here.
Abstract: An underwater viewing system based on holographic principles has been presented at the Second International Meeting on Acoustic Holography.1 Since the conceptual aspects have already been outlined in the previous paper,1 the design and construction criteria for the implementation of such a system are emphasized here.
20 citations
Patent•
08 Jul 1971
TL;DR: In this paper, the system is designed to operate as close to the GEOMETRICAL OPTICS LIMIT as is physically possible, and the system operates in a two-dimensional space.
Abstract: FOURIER TRANSFORMS ARE PRODUCED ON AN OUTPUT PLANE WHEN INPUT IMAGES ARE PROJECTED BY MEANS OF SPATIALLY INCOHERENT LIGHT THROUGH A PAIR OF TRANSPARENCIES EACH HAVING A FRESNEL ZONE PATTERN THEREON. THE SYSTEM IS DESIGNED TO OPERATE AS CLOSE TO THE GEOMETRICAL OPTICS LIMIT AS IS PRACTICALLY FEASIBLE.
11 citations
TL;DR: The design and the spark-erosion production technique for circular Fresnel zone plates with focal lengths between 3 m and 40 m when illuminated by a HeNe laser emitting light at 633 nm is described and their image pattern is theoretically investigated.
Abstract: This paper describes the design and the spark-erosion production technique for circular Fresnel zone plates with focal lengths between 3 m and 40 m when illuminated by a HeNe laser emitting light at 633 nm. Their image pattern is theoretically investigated by modifying Lommel’s original approach to the problem in order to determine the effects of a decentered beam, varying zone numbers and a range of gaussian illumination parameters. The equations derived are evaluated and their results graphically illustrated. The theoretical predictions are experimentally verified for three typical zone plates. The results are discussed with particular regard to their bearing upon the use of zone plates as the optical reference elements in an alignment system at present in an advanced stage of development at the U.K. National Physical Laboratory.
11 citations
TL;DR: In this paper, the concept of effective number of Fresnel zones is used in order to discuss some properties of the losses of the open resonators, as functions of the resonator geometry.
Abstract: The concept of "effective" number of Fresnel zones is used in order to discuss some properties of the losses of the open resonators, as functions of the resonator geometry. The cases of the flat-roof resonator and the step-rim resonator are discussed in detail.
4 citations
TL;DR: In this article, the authors investigated the power transfer between two ellipsoidal reflector antennas with common focal points and dual-mode feeds, assuming a circularly symmetric feed pattern, the H-plane pattern of an open-end circular waveguide excited by the TE 11 mode, the maximum transmission coefficient between reflector apertures was found to be within 0.5 percent of the value computed for transmission between two circular aperture with optimum illumination described by the generalized prolate spheroidal function.
Abstract: Power transfer between two ellipsoidal reflector antennas with common focal points and dual-mode feeds has been investigated. Assuming a circularly symmetric feed pattern, the H-plane pattern of an open-end circular waveguide excited by the TE 11 mode, the maximum transmission coefficient between reflector apertures is found to be within 0.5 percent of the value computed for transmission between two circular apertures with optimum illumination described by the generalized prolate spheroidal function. Transmission loss between two reflector antennas versus illumination taper is computed for various values of the parameter [p = (ka 1 a 2 )/R]. The minimum transmission loss is obtained as a compromise between feed spill-over and aperture transmission efficiency. In view of the inconvenience of building different ellipsoidal reflectors for different antenna spacings in order to achieve maximum power transfer, we examine the feasibility of using a defocused ellipsoid to simulate ellipsoids of different focal lengths. The deviation of the aperture phase distribution of a defocused ellipsoid from a required spherical phase front is approximately given by an explicit expression. A simple upper bound of the transmission loss due to small phase deviation is obtained for a given maximum phase deviation.
2 citations