ISSN:0030-3909    

DOI:10.1080/713820298

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Intensity fluctuations arising from a random walk in 2α dimensions are governed by the gamma-distribution of parameter α. When 2α is fractional, conventional methods of calculating statistical properties of the integrated intensity, based on a gaussian noise theory approach, can no longer be used. In this paper the single interval statistics of an integrated gamma-distributed variable with lorentzian spectrum are derived directly from a rate equation for the process. The results include, as a special case, the integrated photon statistics predicted by a model for single-mode thermal radiation in a cavity.

ISSN:0030-3909    

DOI:10.1080/713820299

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

ISSN:0030-3909    

DOI:10.1080/713820303

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

This paper presents the theoretical basis of a technique for observing reflecting surfaces which have been perturbed from a completely plane configuration. Surface distortions that are uniform in one direction are considered, a case relevant to the observation of long-crested water waves. The technique employs the direct visual or photographic observation of the reflections of straight-line sources in the surface, and is a commonly used and extremely simple technique for the examination of water-surface phenomena. Expressions are found for the observed image shape in terms of the shape of the surface and the relative dispositions of the light source and the observer, for the case in which the source is held parallel with the undisturbed surface at the same height as the observer. Experiments are described, using a reflecting solid surface of known profile, and the observed images are shown to be closely in agreement with the predictions of the theory. A qualitative explanation of the relation of the image to the surface shape is given and the conditions are examined for the occurrence of gaps in the image as the surface distortions become steep.

ISSN:0030-3909    

DOI:10.1080/716099517a

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

The theoretical investigation of the use of a long straight-line light source and a camera to determine the profiles of reflecting surfaces, started by Gilbert and Scott [1], is continued. In the earlier paper, expressions were found describing the observed image in terms of the configuration of the apparatus and the surface shape for surfaces whose cross-section is uniform in a fixed direction. In this paper, these expressions are inverted, so that the surface profile may be deduced from the observed image. The inversion process is shown to be equivalent to the problem of solving a certain ordinary differential equation with appropriate boundary data, but it is found that the problem does not have a unique solution. The use of a second photograph yields a problem which does admit a unique solution, and for some configurations of the apparatus, a solution in closed form is found. Numerical experiments to test the ordinary differential equation and the closed form of solution, and practical experiments to check the prediction of non-uniqueness are described.

ISSN:0030-3909    

DOI:10.1080/716099517

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

This paper presents an investigation of the self-focusing of an elliptically gaussian laser beam propagating along the static magnetic field in a non-linearly absorbing magnetoplasma. The electron concentration and temperature and the static magnetic field are allowed to be non-uniform. The direct coupling as well as the indirect coupling between the right- and left-handedly polarized modes has been taken into account. Coupled equations for the beamwidth parameters have been derived by using the Akhmanov approach. It is seen that axial symmetry of the intensity distributions of the two modes is not preserved in the presence of the direct coupling. The variations of the beamwidth parameters become considerably aperiodic on account of the indirect coupling and non-uniformity in the plasma parameters. Though the investigation is explicitly related to a magnetoplasma, the analysis presented herein can be easily extended for some other anisotropic media.

ISSN:0030-3909    

DOI:10.1080/713820313

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

A digital method of evaluating holographic interferograms obtained with dual object illumination is introduced. By shifting the interference field phase the total interferometric content can be reduced to in-plane displacement information. Electronic processing permits fast automatic evaluation with a high degree of accuracy.

ISSN:0030-3909    

DOI:10.1080/713820296

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

The purpose of the work is to specify tolerances for the alignment of binocular instruments. Contrast threshold levels, time-to-fuse and accommodation were recorded for binocular view of a target at a distance of 1·3 m, in a group of six observers and under prismatic conditions requiring a range of different horizontal and vertical fusional responses. It is confirmed that the derived values of binocular summation are maximal when the prism arrangement corresponds to natural viewing of the target. Values of convergence, divergence or supravergence in excess of 1° from this natural condition produce significant reductions in binocular summation. Measurements of time-to-fuse reveal rate differences between the horizontal and vertical fusional mechanisms and further produce a more stringent condition, 0·5°, on supravergence tolerance. Measurements using a speckle optometer show only small changes in accommodation over the whole investigated ranges of vergence and provide clues to the mechanism of the observed reduction in binocular summation.

ISSN:0030-3909    

DOI:10.1080/713820316

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

ISSN:0030-3909    

DOI:10.1080/713820304

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Incoherent diffraction imagery formed by a polarizing microscopy with crossed polarizers is studied. Closed form solutions are obtained for the cumulative point spread function, the line spread function, and the edge spread function. Representative numerical results are displayed. The image of a bar target is also evaluated.

ISSN:0030-3909    

DOI:10.1080/713820301

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor