ISSN:0030-3909    

DOI:10.1080/713820937

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

ISSN:0030-3909    

DOI:10.1080/713820933

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

ISSN:0030-3909    

DOI:10.1080/713820942

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

On the basis of Wolf's wave equations for the propagation of coherence a new, explicit representation of the cross-spectral density function is obtained in terms of a generalized radiance function which is constant along geometrical rays. By means of a series development of this representation it is shown that the laws of classical radiometry and free space radiative transfer are valid provided the radiance function (the specific intensity) may be considered constant over distances comparable to the transverse coherence length. The corresponding expression for the cross-spectral density function is identical to a result previously obtained by Ovchinnikov and Tatarskii and implies that, forquasi-homogeneous wavefields, the radiance function is everywhere uniquely related to the field coherence by a generalized van Cittert-Zernike theorem. Furthermore, by use of the central limit theorem, the field statistics are shown to be gaussian, so that a complete statistical description is provided in terms of the phenomenological radiance function. The analogy of this statistical model with kinetic descriptions of transfer phenomena in other fields of physics is discussed.

ISSN:0030-3909    

DOI:10.1080/713820948

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

A method of picture reconstruction from image projections using the principle of discrete coincidence is presented. Discrete input information is processed directly in computer operations to yield discrete output information without interpolation to obtain intermediate continuous quantities. Points seen by less thannviews out of a total ofmviews at different angles are rejected, wheren(m) is the coincidence criterion. In general, 3,⩽n(m)<mand the coincidence criterion is also a function of other design parameters: ray width, dead width and flux intensity. The algorithm is simple and lends itself to easy implementation on hardware.

ISSN:0030-3909    

DOI:10.1080/713820947

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

Quantitative microscope interferometry has, until recently, been limited to observations at small apertures with, consequently, limited image brighteness and resolution. Also, in the beam splitting comparison techniques, specimen shape and area are necessarily limited because of the requirement for an adjacent background reference area. We have previously described a quantitative finite aperture theory (FAT) for incident light interferometry which avoids these endemic problems and operates with cones of incident light having included angles between 30° and 105°. In addition to determining thicknesses, it is possible to derive film refractive index by making measurements at several different apertures, a unique feature among optical methods because it is capable of measuring over areas less than 0·05 wm2. We report here new measurements which confirm the correctness of finite aperture theory to a high level of precision.

ISSN:0030-3909    

DOI:10.1080/713820943

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

Optical bleaching of F centres has been studied in radiation-coloured NaCl crystals. It has been shown that the amounts of different aggregates (R, M and N) generated due to the bleaching are strongly dependent on the bleaching intensity at a certain total energy falling upon the crystal. This observation is of importance when looking for optimum conditions for holographic recording on colour centres.

ISSN:0030-3909    

DOI:10.1080/713820941

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

Observations of the solar diameter and shape are of considerable interest for astrophysicists dealing with the interior structure, rotation, pulsations and evolution of stars. Also there has been considerable interest in longterm variations in the solar output and diameter as it relates to climatic variations. The paper describes an experiment which holds promise for accomplishing these observations with very high precision over a long period of time. With it, it might even be possible to detect the gradual evolutionary change of the Sun within decades. More rapid changes related, for example, to climatic variations on Earth would be detectable in a short time. The experiment has a component both in space and on Earth. The space component consists of a flat reflector 1–2 m in diameter in geostationary orbit. It acts as a reflecting pin-hole telescope forming an image of the Sun on the Earth 350 km in diameter. The earth component consists of the machinery needed to measure this image. This paper elaborates on these concepts and defines problem areas which need further studies.

ISSN:0030-3909    

DOI:10.1080/713820939

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

We examine and optimize the image quality of a laser recorder based on a multi-beam acousto-optical modulator producing a vertical fan of beams and a light deflector for scanning the beams horizontally. Besides the first-order scattered image-forming raster beams, some ‘parasitic’ beams due to threephonon scattering are also generated in the modulator. These beams interfere with the raster beams in the image plane of the recorder and give rise to spatial fluctuations of the exposure recorded along a line. We show that the horizontal distributionẼ(x) of the total energy incident on a vertical line is given by a sum over differences of the optical frequencies of the different beams, where each term is the product of the number of intermodulations at the given frequency, a cosinusoidal factor and a ‘noise transfer function’ depending only on the system parameters and the spatial frequency. We introduce a SNR defined as reciprocal of the relative RMS variation ofẼ(x) and evaluate its dependence on the system parameters and the acoustic carrier frequencies. We minimize the effect of intermodulations by finding sets of carrier frequencies that maximize the RMS and the minimum of the intermodulation frequencies respectively, and we calculate numerically the SNR for different distributions of acoustic frequencies.

ISSN:0030-3909    

DOI:10.1080/713820935

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

A new type of image dissector tube is described. The tube contains new electro-optics involving a combination of ring-electrodes and a metallic mesh. The positioning of the mesh is determined by a relation involving the number of focusing loops. The LRM tube (from loop-related-mesh positioning) implies that very high resolution can be obtained at fairly low accelerating voltages. The resolution is uniform over the whole photocathode when dynamic focusing is used. The high resolution is obtainable in tubes where the ratio between the photocathode diameter and the length of the image section is as high as 0·4. Thus large photocathodes can be combined with short tube lengths. An LRM tube design with a 100 mm photocathode diameter and an image section 250 mm long is described.

ISSN:0030-3909    

DOI:10.1080/713820940

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor