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Showing papers on "Fresnel zone published in 1985"


Journal ArticleDOI
TL;DR: In this article, images formed under incoherent illumination by two gratings in tandem are analyzed using the theory of grating imaging, and the images are categorized on the basis of various integer parameters that arise in the analysis.
Abstract: The images formed under incoherent illumination by two gratings in tandem are analyzed using the theory of grating imaging. The images are categorized on the basis of various integer parameters that arise in the analysis. A transfer function is introduced for describing the imaging process. The image positions are related to the foci of a Fresnel zone plate.

69 citations


Proceedings ArticleDOI
24 Oct 1985
TL;DR: In this article, the use of the Fresnel zone plate as a focusing or frequency-filtering device at millimeter wavelengths is discussed and sample design data are given, as well as references to prior results.
Abstract: A description is given of the use of the Fresnel zone plate as a focusing or a frequency-filtering device at millimeter wavelengths. Sample design data are given, as well as references to prior results. A newer type of zone plate is discussed which employs two dielectrics of equal thickness to produce a flat zone plate.

42 citations


Proceedings ArticleDOI
20 Jun 1985
TL;DR: In this paper, a VG HB5 STEM has been modified to allow computer controlled contamination writing on thin Carbon substrates, with line widths of 20 nM and height to width aspect ratios of better than 5:1.
Abstract: A VG HB5 STEM has been modified to allow computer controlled contamination writing on thin Carbon substrates. Line widths of 20 nM and height to width aspect ratios of better than 5:1 can be drawn. This writing has been used to fabricate Fresnel zone plates. A patching process is involved with registration to an accuracy of 2.5 nM. Methods and techniques have been developed to compensate for non-linearity of the field scans together with specimen drift. Zone plates of 50 NM diameter and outer zone widths of 40 nM have been con-structed.

22 citations


Journal ArticleDOI
TL;DR: Two-dimensional sine, cosine, and Fourier transforms are obtained for objects illuminated by spatially incoherent, bandlimited light for bias removal and shot-noise level performance using a 14-bit digitizer.
Abstract: Two-dimensional sine, cosine, and Fourier transforms are obtained for objects illuminated by spatially incoherent, bandlimited light. A lensless Fresnel zone processor consisting of a double-imaging interferometer, a CCD array, and a digital computer is described and analyzed. Excellent bias removal and shot-noise level performance are obtained using a 14-bit digitizer. Experimental optical transforms are presented for an offset circular aperture and for a binary zone plate transmittance. The space–bandwidth product is derived, and excellent comparison with experiment is obtained.

18 citations


Journal ArticleDOI
TL;DR: In this article, a laser photoplotter was used to study the interaction of a continuously moving focused laser beam with chromium films deposited on glass substrates, and the dependence of the widths of the tracks which were formed on the velocity of motion of the light spot and on the applied power was investigated.
Abstract: A technology was developed for synthesizing optical diffraction elements utilizing thin chromium films. It consists in directing a focused laser beam onto a substrate rotating at a constant angular velocity and coated with a thin chromium film, and subsequently processing it chemically in a selective etchant. Experiments were performed using a laser photoplotter to study the interaction of a continuously moving focused laser beam with chromium films deposited on glass substrates. The dependences were investigated of the widths of the tracks which were formed on the velocity of motion of the light spot and on the applied power. The new technology was used to show that diffraction structures having a resolution of better than 1000 mm−1 could be recorded. The practical possibilities of the technology were illustrated by preparing masks for Fresnel zone plates having a numerical aperture of 0.65 and a diameter of 47 mm, at a wavelength of 0.63 μ. The energy distribution in the Airy disk of these plates was close to the diffraction limit.

17 citations


Journal ArticleDOI
TL;DR: In this article, the radial distribution of irradiance in a Fresnel diffraction pattern behind a circular aperture illuminated by a plane wave was measured using the Fresnel-Kirchhoff theory.
Abstract: The Fresnel–Kirchhoff theory is used to derive formulas which permit rapid calculation by personal computer of the radial distribution of irradiance in a Fresnel diffraction pattern behind a circular aperture illuminated by a plane wave. An experiment to measure the radial distribution of irradiance is described. The experimental results are in good, but not complete, agreement with the theory.

16 citations



Proceedings ArticleDOI
21 May 1985
TL;DR: In this paper, the authors discussed several procedures with emphasis on a photographic technique which offers the greatest accuracy in estimating the radio horizon at short distances and at low vertical look angles, respectively.
Abstract: Air-to-ground propagation at 900 MHz exhibits some fading characteristics similar to land-based mobile radio systems and others similar to terrestrial line-of-sight microwave systems. 900 MHz air-to-ground propagation, over long distances and at low vertical look angles, is governed primarily by obstacles blocking the path. At shorter distances the signal sometimes experiences multipath fading. The level varies slowly as the aircraft passes in and out of fresnel zones. When the aircraft is over a ground station, the signal experiences rapid fading similar to land mobile systems. At 900 MHz, with a limited fade margin, the radio horizon is approximately equal to the optical horizon. The horizon can be documented in a variety of ways simplifying the coverage prediction process. Several procedures are discussed with emphasis on a photographic technique which offers the greatest accuracy.

13 citations


Journal ArticleDOI
TL;DR: A new phase zone plate with suppressed higher-order flux is proposed and optimum design calculations are made for Al.asp in the 300–600-A wavelength range.
Abstract: A new phase zone plate with suppressed higher-order flux is proposed and optimum design calculations are made for Al. While the first-order collecting efficiency is equal to that of conventional Fresnel zone plates (∼10%), the ratio of the higher-order flux energy to the first-order energy can be suppressed to <10−3–10−6 in the 300–600-A wavelength range.

13 citations


Journal ArticleDOI
TL;DR: In this paper, the temporal coherence of the observed field is analyzed when a nonabsorbing phase screen is moved at constant velocity in front of an aperture illuminated by quasi-monochromatic plane-wave illumination.
Abstract: We consider how the coherence of the observed field is affected by propagation when a nonabsorbing phase screen is moved at constant velocity in front of an aperture illuminated by quasi-monochromatic plane-wave illumination. It is shown that when the rms value of the profile is not too large, there is always a component of transmitted light whose temporal coherence is unaffected by the motion of the phase screen. Closed-form expressions for the temporal coherence of the observed field are obtained for the following cases: (1) a point aperture, (2) the Fraunhofer region, and (3) limiting cases of Fresnel diffraction for relatively large- and small-grain scatterers. Numerical results are presented.

8 citations


Book ChapterDOI
01 Jan 1985
TL;DR: In this paper, a tutorial review of sound propagation in a random ocean is presented, with emphasis on the oceanography and the statistics of received signals, and a list of references should help the reader who wishes to investigate further specific aspects of the problem.
Abstract: A tutorial review of sound propagation in a random ocean is presented, with emphasis on the oceanography and the statistics of received signals. The list of references should help the reader who wishes to investigate further specific aspects of the problem.

Journal ArticleDOI
A. VanderLugt1
TL;DR: The optimum geometry for obtaining the maximum time spreading for a given signal bandwidth is derived and a permutation of time samples can be achieved and illustrated some of the key features through simulations.
Abstract: In the analysis of coherently illuminated optical systems we distinguish between space planes and spatial frequency or Fourier planes. Between these two planes exists a continuum of Fresnel transform planes; the Fresnel domain therefore shares, more or less equally according to its position, the properties of the space and frequency domains. Since Fresnel transforms are space-variant operations, generalized results are difficult to obtain. When implemented by Bragg cell processors, however, Fresnel transforms have some interesting and useful spatial/temporal properties. We examine the application of Fresnel transforms to analog signal scrambling techniques. We derive the optimum geometry for obtaining the maximum time spreading for a given signal bandwidth. We derive the system response to impulse, short pulse, and cw signals. We show how a permutation of time samples can be achieved and illustrate some of the key features through simulations.

Journal ArticleDOI
TL;DR: The generalized symmetry-restricted output efficiency maximizing zone plate (GSEZP) as mentioned in this paper is the optimal solution for materials of arbitrary indices of refraction, where k is the absorption constant and δ is the phase-difference constant.
Abstract: A zone-plate transfer function of importance in practical optical systems is the output efficiency, I(1)/IOUT, where I(1) is the total power diffracted into the first order by the zone plate. We apply variational analysis to derive a special symmetry-restricted zone-plate profile that maximizes this output efficiency. Our solution, which we have named the generalized symmetry-restricted output efficiency maximizing zone plate, is demonstrably the optimum such symmetry-restricted solution for materials of arbitrary indices of refraction n^ [n^=(1-δ)+ik], where k is the absorption constant and δ is the phase-difference constant. For purely absorbing materials, i.e., for δ = 0, we show that a simple extension of our general solution in the far field leads to the well-known, but less-efficient, Gabor zone plate, which also has the desirable property of suppressing all diffracted orders higher than the first and minus first. Our theoretical solution, which is optimum in both the near and far fields, is of importance for research in the soft-x-ray range, where most materials are in fact both absorbers and phase shifters, i.e., where neither k nor δ is evanescent.

Patent
Hanspeter Küpfer1
15 Mar 1985
TL;DR: In this article, an antenna arrangement for a radar test apparatus with a radiator (S), which is able to be oriented at least approximately against the antenna (RA) of the radar apparatus (RG) to be examined, the directional axis of which is to be adjusted and/or adjusted, for simulating a target signal emanating from a virtual radiation centre, emits a test signal as wave front, is described.
Abstract: 1. Antenna arrangement (A) for a radar test apparatus with a radiator (S), which is able to be oriented at least approximately against the antenna (RA) of the radar apparatus (RG) to be examined, the directional axis of which is to be examined and/or adjusted, and for simulating a target signal emanating from a virtual radiation centre, emits a test signal as wave front, characterised by the following features : a) the antenna arrangement has a portable, planar, electrically conductive reflector (M) on which a carrier (T) with the mounted radiator (S) is secured at least approximately on the edge and above the conducting plane (MO) of the same, b) the dimensions of the surface of the reflector (M) are selected in such a way that this covers half of the first Fresnel zone in the radiation field, c) for examining the radar apparatus the distance a between the phase centre of the radiator (S) and the conducting plane (MO) is selected such that the direct wave and the wave reflected by the conducting plane (MO) of the reflector (M) support each other maximally at the location of the antenna (RA) of the radar apparatus (RG) to be examined and thus the base point (Q) of the vertical line from the phase centre of the radiator (S) onto the plane reflector (M) forms the virtual radiation centre of the antenna arrangement (A).


Book ChapterDOI
01 Jan 1985
TL;DR: In this article, backscattering from the seafloor from an explosive sound source is received by an array and processed to form images of backscatter features of the sea floor and to estimate scattering strength.
Abstract: Backscattering from the seafloor from an explosive sound source is received by an array and processed to form images of backscattering features of the seafloor and to estimate scattering strength. The images are helpful in determining parameters used for calculating scattering strengths of specific physiographic features and understanding the results. Images of some features are improved by processing with a non-linear technique. Reverberation measurements in the Tyrrhenian Sea show that scattering from the coastal margin occurs in two distinct zones. Scattering strength increases slowly with frequency over the 700 Hz band.

Patent
21 Sep 1985
TL;DR: In this article, a single element plate lens with a high numerical aperture is obtained by forming a fine striped pattern like a hologram lens and a Fresnel lens on both surfaces of a transparent plate.
Abstract: PURPOSE:To obtain the single element plate lens with a high numerical aperture which converges laser light into a fine spot by forming a fine striped pattern like a hologram lens and a Fresnel lens on both surfaces of a transparent plate. CONSTITUTION:A hologram or Fresnel zones 2 and 3 are formed on both surfaces of the transparent plate 1. Incident laser light (a) is converged through the striped pattern 2 toward a point P as a light beam (b) and the numerical aperture sintheta1 at this time is 0.2-0.3 at most. Then, it is converged on a point Q as a light beam C through the striped pattern 3 and the numerical aperture sintheta2 is increased to about 0.5, but the striped pattern 3 operates as a lens with a 0.2- 0.3 numerical aperture to the light beam (b), and aberrations are reduced enough to ignore.

Journal ArticleDOI
TL;DR: In this article, a review of recent experimental and theoretical studies of the influence of the sea surface on the transmission of airborne sound into the ocean is presented, where the authors focus on conditions where the refracted grazing angle is greater than approximately 30° since the loss is very large for smaller angles.
Abstract: This is a review of recent experimental and theoretical studies of the influences of the sea surface on the transmission of airborne sound into the ocean. Most applications will depend upon conditions where the refracted grazing angle is greater than approximately 30° since the loss is very large for smaller angles. For grazing angles larger than 30°, two parameters serve fairly well to characterize the transmission loss through the sea surface. The first is a roughness parameter R which is equal to the sea wave height measured in airborne sound‐speed wavelengths. The second is a diffraction parameter DL which is equal to the Fresnel zone diameter measured in correlation lengths of the sea surface slopes. When R is less than unity and DL is less than 3, there is usually no effect due to surface roughness. When either condition is not satisfied, there is usually more transmission loss than there would be through a flat surface. Exceptions to this depend upon the refracted grazing angle and upon the angle b...

Patent
20 Nov 1985
TL;DR: In this article, the authors proposed a method to enable alignment of stability and high accuracy by preventing the phenomenon of light disturbance in a target made of resist by a method wherein a plurality of concentric rings constituting the Fresnel zone target are composed of assemblages of micro plane parts each isolated at micro intervals.
Abstract: PURPOSE:To enable alignment of stability and high accuracy by preventing the phenomenon of light disturbance in a target made of resist by a method wherein a plurality of concentric rings constituting the Fresnel zone target are composed of assemblages of micro plane parts each isolated at micro intervals. CONSTITUTION:The surface of an Si substrate 17 is coated with a thin film of SiO2, polycrystalline Si, Al, or the like, which is then patterned into the Fresnel zone target 10. In this construction, the target 10 is composed of four concentric rings 11-14 as a whole, and the widths and the gaps of the respective concentric rings 11-14 in the radius direction are successively reduced from the center toward the periphery. In such a manner, micro plane parts 11b-14b are generated in the concentric rings 11-14, thus making the coating state uniform when the whole surface is coated with the resist 16, and making the film thickness of each part uniform. Such a manner can prevent the light disturbance due to light interference at the time of alignment; then, stable diffraction is caused, and the alignment becomes increased in accuracy.

01 Jan 1985
TL;DR: In this paper, the authors explain the axial intensity maximum from the geometrical focus toward the diffracting aperture, known as the focal shift, in terms of the asymmetry of the Fresnel diffraction about focus.
Abstract: The migration of the axial intensity maximum from the geometrical focus toward the diffracting aperture, known as the focal shift, is explained in terms of the asymmetry of the Fresnel diffraction about focus. Conditions for the reversal or elimination of the focal shift are predicted. 8 refs.

Patent
16 Feb 1985
TL;DR: In this paper, the Fresnel zone plate is made by an interference on a plane plate P of two optical waves of luminous flux W1 and W2, and if a wavelength is the same as a wavelength of a recording light source in case of condensing a light from a point O to I, the focal position is constant with regard to any annular zone.
Abstract: PURPOSE:To reduce an aberration in case a titled zone plate is used by a shorter wavelength than a wavelength used for a holography by recording an interference fringe by the holography on a curve surface which is curved symmetrically in its rotation. CONSTITUTION:In case a Fresnel zone plate is made by an interference on a plane plate P of two optical waves of luminous flux W1 and W2, it is the same as what is called a hologram of a point image, and if a wavelength is the same as a wavelength of a recording light source in case of condensing a light from a point O to I, the focal position is constant with regard to any annular zone, and a point image of non-aberration is obtained in a position of I. In case the Fresnel zone plate prepared in this way is used by other wavelength than a wavelength of a recording light source, a large aberration is generated and it does not become practical, therefore, the aberration is corrected by forming a hologram of a point image on the spherical surface. That is, in case a relative relation of the recording light source is constant, the aberration can be corrected by forming the zone plate to a spherical surface, therefore, the Fresnel zone is improved remarkably by forming it on a curved surface.


Book ChapterDOI
01 Jan 1985
TL;DR: This chapter devotes itself to illustrating methods for solving specific problems, and also serves as a collection of practical examples involving diffraction phenomena.
Abstract: The best way to understand the principles associated with a given discipline is through examples which apply these principles. This chapter devotes itself to illustrating methods for solving specific problems, and also serves as a collection of practical examples involving diffraction phenomena.