ISSN:0030-3909    

DOI:10.1080/713820870

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

A significant improvement in instrument efficiency can be obtained through the use of high-efficiency coatings. Their implications on cost, complexity and operation of the instrument are discussed. Moreover, it is essential to have the possibility of assessing the real performances of such coatings. An instrument able to measure coating efficiency on almost any kind of substrate has been successfully built.

ISSN:0030-3909    

DOI:10.1080/713820863

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

A diamond window was used in the Pioneer Venus I.R. radiometer. The paper suggests that diamond should be considered more widely as a possible optical component for windows and small lenses in space-optics and other optical applications. The cost is not high in relation to other costs involved in space research or for some land-based instruments. The optical properties of type II diamond are (i) transparency from 230 nm to far infra-red (with only weak absorption in the near infra-red), and (ii) high refractive index (2·43). Mechanically, diamond is the strongest of all solids and strong vacuum-tight joints to metal can be made. The thermal conductivity is better than copper. The main difficulty and cost is in working surfaces (other than flats) to optical tolerances.

ISSN:0030-3909    

DOI:10.1080/713820872

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

This paper describes an experiment in narrow spectral band speckle interferometry, which uses variations in the spectrum across the astronomical object under study, to obtain information of the object on the millisecond of arc scale. We plan to apply this experiment to the study of spectroscopic double stars, stellar rotation, spectroscopic and magnetic variable stars and other astronomical objects.

ISSN:0030-3909    

DOI:10.1080/713820871

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

Microwave holography differs from optical holography in three distinct ways. First, in microwave holography the reference field may be eliminated and replaced by correct phasing of the local oscillator within the microwave receiver. Second, the reference wave need not coexist in time with the signal or object field. Third, it is not necessary that the object field be measured simultaneously across the array. Aside from these fundamental differences, which give the microwave holographer additional freedom in system design, another practical difference should be noted. Because of the long wavelength used in microwave holography, the aperture must be huge to obtain images with fine resolving power. Such apertures are often mechanically unstable. By introducing adaptivity or self-cohering into the creation and measurement of the reference field, it is possible to ‘straighten out’ a distorted microwave aperture. An instrument which performs these operations is called a radio camera. A twodimensional radar map of a few blocks of a small town in Pennsylvania illustrates the process.

ISSN:0030-3909    

DOI:10.1080/713820868

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

We have already reported the correction of a spectrum observed by a monochromator by means of the optical transfer functions (OTF). In these reports, the grain of a film produced a noise which could be contained in the line profile of a corrected spectrum and the line spread function was used to determine OTF. Therefore, in this study the process of smoothing noise by means of the method of least squares was performed, and then the correction of the spectrum was made. We already knew that the signals and the grains make products which represent the intensity of the light which transmits through films. After considering and examining these relationships, we conclude that the correction of a spectral image by means of OTF is difficult to make, unless the process of smoothing is performed on the noise included in signals.

ISSN:0030-3909    

DOI:10.1080/713820883

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

A simple method for on-line microwave imaging with very high resolution is presented. The imaging principle is based on the use of a synthetic aperture. Resolution is in one dimension but can be extended to two dimensions. Experimental results for one- and two-dimensional imaging are shown.

ISSN:0030-3909    

DOI:10.1080/713820878

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

Direct photographic work over a large field (1°) at the prime focus of the classical Canada-France-Hawaii 3·6 m telescope has been achieved with very good image quality (less than 0·5 arcsec FWHM). The basic characteristics of the wide-field corrector (overall image quality, optical lay-out) based on an original design by Wynne are presented. Our Wynne corrector was in fact redesigned to have the last optical surface flat so that a transmission grating could be replicated thereon. There are three interchangeable last elements, those with gratings being wedged in proportion to the dispersion. This arrangement with only three optical elements locates the gratings at a maximum distance from the focal surface resulting in improved resolution over a 1° field, two times larger than that for the five element arrangement at KPNO. The CFH telescope grating-plus-lens, or ‘grens’ has a brightness limit which is fainter than the Palomar Sky Survey.

ISSN:0030-3909    

DOI:10.1080/713820881

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

A flat-field fastf-ratio reflecting focal reducer which consists of two mirrors is described (figure 1). It can be used particularly for the Cassegrain focus withf-ratio 4–6, and thus anf-ratio 1–2 can be obtained. By way of removing the secondary mirror of the Cassegrain system and choosing the shapes of the two mirrors of focal reducer, not only can the third-order spherical aberration, coma, astigmatism and curvature of field be eliminated simultaneously, but the high-order aberration can also be reduced. This focal reducer has a field of view of 12-24 arc min and its focus is accessible. In this paper an example and its spot diagram are given. A modification of the focal reducer can also be used for prime focus.

ISSN:0030-3909    

DOI:10.1080/713820884

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

The relationship between signals and graininess on radiographs is discussed. It has been reported that the signals are reproduced by Fourier inverse transform even though the spectra of signals are cut off. For this reason, it is considered that the intensity of light which is transmitted through films produces the products of the signals and the radiographic mottles. However, the following could be obtained experimentally: those products which are produced by the signals are the grains of films from the radiographic mottles, and the brightness of reproduced images is related to the size of grains.

ISSN:0030-3909    

DOI:10.1080/713820869

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor