摘要:

The degree of spatial coherence S n12(0) S has been measured for a CO2laser beam of radiation emerging from a central output-coupling hole, or four output-coupling holes in the centre-symmetric annular region, in a plane mirror of the Fabry-Perot resonator. The effects of these two kinds of output-coupling apertures on the spatial coherence are studied in association with mode structure in the resonator. The value of S n12(0) S is always above 0·9 for two points in any location in the beams of radiation emerging from the four output-coupling holes, while it varies with the time in the range 0·5 to 1·0 in a beam of radiation emerging from the central output-coupling hole. Some analytical considerations are given, according to which the value of S n12(0) S should be approximately unity over the cross-sectional area of a beam of radiation emerging from an output-coupling hole of 6 mm in diameter. This is partly in agreement with the results of the measurements. For the central coupling hole, the fact that S n12(0) S varies with time is explained qualitatively to be due to the intensity fluctuation in every operating mode, competing with each other in the active resonator. For the four coupling holes a particular mode may be made to survive due to relatively strong mode competition arising from the mode selective effects of the off-centred four coupling holes. On this account a high value of S n12(0) S may be obtained at two points in the beam separated by 25 mm.

ISSN:0030-3909    

DOI:10.1080/713818408

出版商:Taylor & Francis Group    

年代:1971

数据来源: Taylor

摘要:

Time averaged as well as doubly exposed speckle patterns of in-plane moving objects are studied. These speckle patterns are recorded photo-graphically; their Fourier transform shows, interference fringes corresponding to the lateral displacement of the object. It leads to a very simple engineering tool for the analysis of mechanical vibrations as well as lateral displacements. Theoretical and experimental results will be shown.

ISSN:0030-3909    

DOI:10.1080/713818406

出版商:Taylor & Francis Group    

年代:1971

数据来源: Taylor

摘要:

The use of non-uniform sampling in optical processing is considered. The filtering operations needed to recover the spectrum of a non-uniformly sampled band-limited function are examined. Serious limitations are shown to exist for markedly non-uniform sampling.

ISSN:0030-3909    

DOI:10.1080/713818409

出版商:Taylor & Francis Group    

年代:1971

数据来源: Taylor

摘要:

Die Durchlässigkeit und das Reflexionsvermögen von Beryll, Topas, Datolith und Zoisit wurde mit Hilfe eines Gitter-Polarisators für Wellenlängen zwischen 1 w m und 5 w m bzw. zwischen 7,5 w m und 15 w m gemessen. Die Spektren zeigen charakteristische Unterschiede, je nachdem die Schwingung parallel oder senkrecht zur optischen Achse (Beryll) bzw. parallel zura-b- undc-Achse (Topas, Zoisit) bzw. parallel oder senkrecht zur 1. Mittellinie erfolgt (Datolith). Vom Beryll wurden farblose, grüne und blaue Kristallvarietäten untersucht. Die Dotierungen der Kristalle, durch welche die verschiedenen Farben verursacht werden, beeinflussen sowohl die IR-Durchlässigkeits- als auch die IR-Reflexionsspektren.

ISSN:0030-3909    

DOI:10.1080/713818405

出版商:Taylor & Francis Group    

年代:1971

数据来源: Taylor

摘要:

Es werden lichtstarke katadioptrische Objektive von einfachem Aufbau beschrieben. Sie bestehen aus einer Vorsatzlinse, zwei Mangin-Spiegeln und einem Bildfeldebnungssystem. Die Objektive haben kleinen sphärischen Zonenfehler (unter 0, 1 ‰f) und bei niedrigen Frequenzen einen hohen Bildkontrast. Sie sind leichter und wirtschaftlicher in der Herstellung als die bekannten Objektive gleicher Leistung.

ISSN:0030-3909    

DOI:10.1080/713818410

出版商:Taylor & Francis Group    

年代:1971

数据来源: Taylor

摘要:

The optimum apodizers have been designed with the tacit assumption that the point-spread functions of the optical instruments that could use them are due to spatially coherent waves. In practice, there is considerable deviation from this ideal condition. In the present paper analytical expressions are given which can be used for a comprehensive study of the performance of the optimum apodizers in partially coherent illumination. The loss of coherence is assumed to be due to atmospheric turbulence. Numerical results concerning the dependence of the encircled energy, the central intensity, the expected resolution etc., for two chosen apodizers show that the performance, in partially coherent illumination, of the optimum apodizers may be contrary to their expected performance. It is therefore very important to take into account the actual state of coherence of the aperture illumination in the designing of apodizers that are to be used under non-ideal conditions.

ISSN:0030-3909    

DOI:10.1080/713818402

出版商:Taylor & Francis Group    

年代:1971

数据来源: Taylor

ISSN:0030-3909    

DOI:10.1080/713818403

出版商:Taylor & Francis Group    

年代:1971

数据来源: Taylor

ISSN:0030-3909    

DOI:10.1080/713818404

出版商:Taylor & Francis Group    

年代:1971

数据来源: Taylor

ISSN:0030-3909    

DOI:10.1080/713818407

出版商:Taylor & Francis Group    

年代:1971

数据来源: Taylor