摘要:

The speckle intensities of both strong scatterers and weak scatterers are modelled as the superposition of N sinusoidal waves whose amplitudes are taken to be correlated random variables in order to account for multipath correlations. Explicit expressions are obtained for the first three moments of the speckle intensity when the correlated amplitudes are gaussian-distributed about a non-zero mean. These moments approach their large-Nasymptotic values independently of the amplitude correlation function. The contrast and skewness parameter are also evaluated, and simplified formulae obtained when N is large. As the number of multipaths become very large, the speckle intensity PDFs tend to limiting functional forms by reason of the central limit theorem; an investigation was made to determine the influence of amplitude correlations on the parameters entering into these limiting functional forms. The implication of these very large-Nasymptotic results is that amplitude correlations are probably not significant in so far as altering the basic structure of the speckle intensity PDF. However, whenNis not large, the amplitude correlations play a significant role.

ISSN:0030-3909    

DOI:10.1080/713820934

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

This paper discusses the radiometric properties of perfectly conductive, slightly rough random surfaces. The Kirchhoff approximation, so far used in this kind of study, is analysed. In particular, its inability to construct models of lambertian rough surfaces is pointed out. The small perturbation method, recently put forward, allows the scope and limitations of this approximation to be established. This method also yields exact expressions for the radiant intensity, for either polarized or unpolarized incident radiation and allows the construction of surfaces which produce a lambertian distribution of intensity.

ISSN:0030-3909    

DOI:10.1080/713820944

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

The present paper describes a new method for measuring the transfer function (TF) of a spectroscopic system by using a sinusoidally modulated spectrum (SMS) and its experimental verification for a plane grating spectrometer of the Czerny-Turner type. The SMS can be obtained by introducing light of broad spectral width into the Michelson interferometer.

ISSN:0030-3909    

DOI:10.1080/713820936

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

A classification of three-mirror systems is given, and their aberrations are described. Systems with the third and main mirrors matched, and plane-field anastigmats are discussed.

ISSN:0030-3909    

DOI:10.1080/713820938

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

The European Southern Observatory (ESO) has immediate plans for the construction of a ‘New Technology Telescope’ (NTT) of about 3–3·5 m aperture and is studying a project for a ‘Very Large Telescope’ (VLT) of 16m equivalent aperture. Some characteristics of these telescopes are discussed, particularly the possibilities of greatly improved optical performance through active optics,closed-loopcontrol. In this connection the problem is approached from the physical origins of the stable or quasi-stable optical aberration function which, apart from high frequency seeing, sets the limits of optical quality of telescopes in practice.

ISSN:0030-3909    

DOI:10.1080/713820945

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

A ‘moth eye’ antireflection surface is a very fine array of protuberances which behaves as a gradation of refractive index, and which substantially reduces the reflectance. The reflection and transmission properties of such surfaces are described, and are shown to be equal to those of the best multilayer antireflection coatings.

ISSN:0030-3909    

DOI:10.1080/713820946

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor