Showing papers on "Physical optics published in 1976"
01 Jan 1976
TL;DR: In this article, the Doppler Reference Record (DRR) was used for anemometrie a : laser a : anemometry a: laser a: anemometric a: a : a : light anemometer b : laser A : laser
Abstract: Keywords: anemometrie a : laser ; anemometrie ; optique ; laser : Doppler Reference Record created on 2005-11-18, modified on 2016-08-08
950 citations
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TL;DR: The double grating shearing interferometry method for determination of the degree of light collimation is described, representing a very strong argument proving the highly diffractive (wave optics) character of the classical Ronchi test.
Abstract: The double grating shearing interferometry method for determination of the degree of light collimation is described. High accuracy is obtained by performing the observation of fringes in the area of the size twice as big as the one usually assumed in shearing interferometry experiments. The conditions under which such a detection mode is feasible are derived. They represent at the same time a very strong argument proving the highly diffractive (wave optics) character of the classical Ronchi test.
65 citations
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TL;DR: In this article, changes in retinal image quality with focus for an aberration-free eye with a 5-mm pupil are discussed in terms of both geometrical and physical optics.
Abstract: Changes in retinal image quality with focus for an aberration-free eye with a 5-mm pupil are discussed in terms of both geometrical and physical optics. Further modulation transfer function curves illustrate the effect of spherical aberration. These theoretical results are compared with analogous experimental data obtained at different wavelengths with quasi-monochromatic illumination, using a double-pass photo-electric, scanning instrument. The comparison shows that the approximations of geometrical optics predict ocular performance quite well, provided that the errors of focus are reasonably large (greater than or equal to 0.5 DS for a 5-mm entrance pupil). Possible sources of error in the experimental measurements are indicated.
63 citations
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TL;DR: In this paper, a uniform low-pass filter model of the scattering process was proposed to estimate the effective surface roughness versus wavelength, and the asymptotic surface height spectral densities fall at least as fast as an inverse cube of spatial frequency.
Abstract: Radio-wave scattering from natural surfaces contains a strong quasispecular component that at fixed wavelengths is consistent with specular-point theory, but often has a strong wavelength dependence that is not predicted by physical optics calculations under the usual limitations of specular-point models. Wavelength dependence can be introduced by a physical approximation that preserves the specular-point assumptions with respect to the radii of curvature of a fictitious, effective scattering surface obtained by smoothing the actual surface. A uniform low-pass filter model of the scattering process yields explicit results for the effective surface roughness versus wavelength. Interpretation of experimental results from planetary surfaces indicates that the asymptotic surface height spectral densities fall at least as fast as an inverse cube of spatial frequency. Asymptotic spectral densities for Mars and portions of the lunar surface evidently decrease more rapidly.
42 citations
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TL;DR: In this paper, an alternative form of Bojarski's POFFIS identity for impulsive point sources was derived for sources of arbitrary time dependence, where the characteristic function is equal to unity in the region occupied by the obstacle and zero elsewhere.
Abstract: The physical optics farfield inverse scattering (POFFIS) identity relates the phase‐ and range‐normalized farfield backscattering amplitude to the spatial Fourier transform of the characteristic function of the scattering obstacle. The characteristic function is equal to unity in the region occupied by the obstacle and zero elsewhere. The original identity was derived by Bojarski for impulsive point sources. Here we extend the result to sources of arbitrary time dependence. We obtain an alternative form of Bojarski’s POFFIS identity. We also derive a POFFIS identity in the time domain. Numerically synthesized checks on the method are provided.Subject Classification: [43]20.30.
35 citations
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TL;DR: In this article, the reconstruction problem of perfectly conducting bodies from far-field scattering data is discussed within the context of physical optics, and the general bistatic scattering configuration, discussed in this investigation, adds inherent complexity to the problem but also introduces possibilities not present in the backscatter limit.
Abstract: The reconstruction problem of perfectly conducting bodies from far-field scattering data is discussed within the context of physical optics. The general bistatic scattering configuration, discussed in this investigation, adds inherent complexity to the problem but also introduces possibilities not present in the backscatter limit.
34 citations
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TL;DR: In this article, the Poynting vector of a plane electromagnetic wave diffracted by the gravitational field of a large spherical body (large compared to its Schwarzschild radius) is given.
Abstract: This paper gives the Poynting vector of a plane electromagnetic wave diffracted by the gravitational field of a large spherical body (large compared to its Schwarzschild radius) and shows in detail how this body works as a gravitational lens. The most interesting results are (1) an extreme amplification of intensity near to the axis of symmetry in the far field behind the body, with a factor of 10 times the Schwarzschild radius divided by the wavelength of the light, and (2) the appearance of double images, differing in shape and position from the predictions of geometrical optics.
32 citations
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TL;DR: In this paper, the higher order corrections to geometrical optics are studied in general relativity for an electromagnetic test wave, and an explicit expression is found for the average energy-momentum tensor which takes into account the first order corrections.
Abstract: The higher order corrections to geometrical optics are studied in general relativity for an electromagnetic test wave. An explicit expression is found for the average energy–momentum tensor which takes into account the first‐order corrections. Finally the first‐order corrections to the well‐known area‐intensity law of geometrical optics are derived.
01 Jan 1976
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TL;DR: In this article, the radiation pattern of a paraboloid is calculated by asymptotic physical optics and geometrical theory of diffraction and the two are compared.
Abstract: Radiation pattern of a paraboloid is calculated by asymptotic physical optics and geometrical theory of diffraction and the two are compared.
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TL;DR: In this article, a physical optics farfield inverse scattering (POFFIS) identity was proposed to generate the image of an anomaly in a plane such as an anticline, syncline, or fault.
Abstract: This paper shows how to process backscattered acoustic data to directly generate the image of an anomaly in a plane such as an anticline, syncline, or fault. The result is based on a physical optics farfield inverse scattering (POFFIS) identity. This identity states that a phase‐ and range‐normalized scattering amplitude is proportional to a function which is unity in the region of the anomaly and zero outside that region.Subject Classification: [43]20.30, [43]20.15; [43]40.50.
01 Mar 1976
TL;DR: In this paper, a focus-fed paraboloid is calculated by asymptotic physical optics (APO) and geometrical theory of diffraction (GTD) for dipole and Huygens source feeds.
Abstract: Radiation pattern of a focus-fed paraboloid is calculated by asymptotic physical optics (APO) and geometrical theory of diffraction (GTD) for dipole and Huygens source feeds. It is shown that the GTD diffraction coefficients are approximations to the PO diffraction coefficients and are valid only in the proximity of the shadow and reflection boundaries. Some errors in the calculation of GTD diffraction coefficients are corrected. Rear radiation is calculated by another asymptotic expansion of the physical optics integral and is compared with the results obtained by other asymptotic techniques. This new expansion is finite in the back direction of the antenna where other methods diverge. Also front to back ratio of a paraboloid, ratio of front radiation to back radiation, is derived by using this new expansion and the results are compared with those predicted by equivalent edge currents method.
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25 Aug 1976
TL;DR: In this article, the authors examined the problem of identifying a target from an analysis of band-limited viewing apertures and showed that the target surface can be identified where the target normal lies within the range of viewing directions; outside of this range, no information is available.
Abstract: : The limited aperture problem of physical inverse scattering is examined i.e., the problem of identifying a target from an analysis of band- limiting viewing apertures. The target may be completely identified from an analysis of high frequency, bandlimited data. If the directions of viewing angles are limited as well, it is shown that the target surface can be identified where the target normal lies within the range of viewing directions; outside of this range, no information is available. It is shown that this phenomenon is totally a feature of the Fourier transform of characteristic (one- zero) functions and independent of the inverse scattering formalism. Numerical examples are given for the case of a perfectly reflecting circular cylinder.
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TL;DR: In this paper, the propagation of the electromagnetic wave field in a nonlinear medium is discussed in the framework of generalized nonlinear geometrical optics, where the nonlinearity of the medium and the angles between the rays and the general orientation of the wave's beam are not assumed to be small.
Abstract: The propagation of the electromagnetic wave field in a nonlinear medium is discussed in the framework of generalized nonlinear geometrical optics. In this approach the nonlinearity of the medium and the angles between the rays and the general orientation of the wave's beam are not assumed to be small. The exact analytical solutions of the equations of this generalized nonlinear geometrical optics are constructed. These solutions show the possibility of a peculiar mechanism of space stratification of the field.
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01 Nov 1976TL;DR: In this article, a critical evaluation of available asymptotic methods for the determination of the near field of parabolic cylinder reflector antennas is made, where the analysis is restricted to reflectors fed at their focus by a line current radiating an E polarisation field.
Abstract: A critical evaluation is made of available asymptotic methods for the determination of the near field of parabolic cylinder reflector antennas. The analysis is restricted to reflectors fed at their focus by a line current radiating an E polarisation field. Reference results, obtained in a numerically precise manner from solutions of the integral equation associated with the rigorous formulation of the radiation problem, serve as the basis of comparison of the asymptotic methods. The latter are the aperture methods, physical optics method and the Keller geometrical optics method in its original and modified forms. This study revelas that: (a) the physical optics method is accurate and reliable for medium and large size reflectors as well as for reflectors with aperture diameters as small as two wavelengths (b) the aperture methods and the modified Keller geometrical optics method are satisfactory for medium and large size reflectors (c) all of the considered asymptotic methods (excepting the Keller method in its original form) lead to results that are practically identical to those of the rigorous theory for reflectors whose diameters exceed or are equal to ten wavelengths (d) the modified Keller method constitutes the best accuracy-calculational economy trade-off for the near field analysis of the parabolic cylinder reflector antennas ordinarily encountered in microwave applications.
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TL;DR: In this paper, a physical optics solution is presented for the scattering of plane waves from a perfectly conducting corrugated surface in the case of waves incident from an arbitrary direction and for an observer far from the surface.
Abstract: A physical optics solution is presented for the scattering of plane waves from a perfectly conducting corrugated surface in the case of waves incident from an arbitrary direction and for an observer far from the surface. This solution is used to compute the radar cross section of the surface in the case of backscatter from irregular (i.e., stochastic) corrugations. An interesting feature of the solution is the occurrence of singularities in the scattered fields. These singularities appear to be a manifestation of focussing by the surface at its "stationary" points. Whether or not the singularities occur in the solution depends on the manner in which one restricts the analysis to the far-field.
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TL;DR: In this article, the first prediction of a molecular structure (intramolecular OI-O of 90°) was made by using optical second harmonic generation measurements on a single crystal of TlIO3 (d311/d333= 0·54).
Abstract: Optical second harmonic generation measurements on a single crystal of TlIO3(d311/d333= 0·54) allow the first prediction of a molecular structure (intramolecular O–I–O of 90°) by such a technique.
01 Feb 1976
TL;DR: In this paper, a basic process for producing 3D isometric images of a radar target from measured multiple frequency scattering data has been modified to image targets with more complex geometrical shape from non-mutually orthogonal look angle data.
Abstract: : A basic process for producing three-dimensional isometric images of a radar target from measured multiple frequency scattering data has been modified to image targets with more complex geometrical shape from non-mutually orthogonal look angle data. Other modifications include changes in the use of the physical optics approximation beyond the shadow boundary, use of polarization diversity information, and estimates of the length to width ratio of the target are given and illustrated. Images produced using these modifications are presented. Recommendations for further research to provide a more versatile imaging procedure are made. The computer programs presently used in the imaging process are given in appendices of the final report. (Author)
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TL;DR: In this article, a nonlinear partial differential equation for the path taken by a light ray in any optical system is defined, based on dynamic programming applied to geometrical optics.
Abstract: Dynamic programming applied to geometrical optics leads to a nonlinear partial differential equation for the path taken by a light ray in any optical system.
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TL;DR: In this article, the Ewald and Oseen apparatus of integral equations in linear optics for nonlinear media has been developed and the relations between micro-and macroscopic values have been found for anisotropic and non-linear media.
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TL;DR: An overview of paraboloidal reflector systems can be found in this paper, where the dyadic Green's function over the currents induced on the reflector is estimated using geometrical optics.
Abstract: Publisher Summary This chapter presents an overview of paraboloidal-reflector systems. The rf performance of paraboloidal reflectors may be analyzed using various techniques of diffraction theory. Such techniques generally involve the integration of the dyadic Green's function over the currents induced on the reflector. These induced currents are estimated using geometrical optics. In principle, however, they may also be calculated using moment-method techniques or by applying classical results to appropriate boundary-value problems. Once the currents are determined, evaluation of the fields becomes straightforward although the computations may be lengthy and laborious. Computers are generally needed for all but a few special cases that may be integrated in closed form. The analysis of the transmitting properties of the antenna is presented in the chapter. An analysis and the geometry of the paraboloid with a prime-focus feed are also elaborated and illustrated. The aperture projection of blocked portions of a paraboloidal reflector is displayed and the classical dual-reflector antenna systems are analyzed. The calculation of radiation from dual-reflector systems by applying physical optics (PO) is also discussed.
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TL;DR: In this paper, the Debye-Sears effect and the frequency fluctuations in a plane light wave induced by atmospheric turbulence and a steady cross wind are discussed, and the intensity law of geometrical optics is generalized to read Iσ/ν2 = constant, where ν is the frequency of the light wave.
Abstract: The basic relations of geometrical optics for the case of an isotropic, time-dependent medium are derived from Fermat’s principle. The time-dependent theory is applied by discussing the Debye-Sears effect and the frequency fluctuations in a plane light wave induced by atmospheric turbulence and a steady cross wind. In the former case it is shown that the Brillouin scattering relation Δω = VΔk holds in the geometrical optics limit where V is the sound velocity, while in the latter case we find, using a method due to Tatarski, that the fluctuations in frequency are of the order of a few kilohertz under the most extreme conditions of turbulence, wind speed, and range. The intensity law of geometrical optics, Iσ = constant, is generalized to read Iσ/ν2 = constant, where ν is the frequency of the light wave.