摘要:

A ray-tracing computer programme has been developed to analyse and design Ebert spectrometers. Using this programme the author has found families of spectrometers that have no astigmatism or coma. In general these spectrometers are usable over only a narrow spectral range, but special cases were found that are suitable for use as scanning monochromators. The monochromators are corrected for these aberrations at all wavelengths, but they require auxiliary folding mirrors. The good performance of the monochromators is due to zero incidence angles of the chief ray at both reflections from the spherical mirror.

ISSN:0030-3909    

DOI:10.1080/713818880

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor

摘要:

Mit einem optisch gepumpten, neodymdotierten Glasfaserbündel ist das Bild eines Diapositivs optisch verstärkt worden. Hierzu war das Diapositiv mit Hilfe eines Neodym-YAG-LASERs durchstrahlt und sein Bild am Eingang des Faserbündels in den optischen Verstärker eingekoppelt, derQ-Switch des LASERs über eine Pockels-Zelle mit der maximalen Besetzungsumkehr in den Glasfasern synchronisiert und das verstärkte Bild über einen synchron getasteten Bildwandler photo ; raphiert worden. Die Verstärkung wird durch zwei Photogramme demonstriert; zur Aufnahme des ersten wurden Verstärker und LASER simultan, zur Aufnahme des zweiten nacheinander betrieben.

ISSN:0030-3909    

DOI:10.1080/713818879

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor

摘要:

On the basis of Huygens' principle this paper considers the diffraction and interference of light traversing side-by-side sound fields at relatively low frequencies by which every order in the diffraction spectrum of light cannot be split but overlapped spatially with one another over the field to be observed. The sound fields greatly modify the spatial coherence state of light, so that the diffraction intensity distribution in the receiving plane depends on the electronically controllable sound pressure. From the analysis of the two-beam interference of light the complex degree of coherence is found to vary from the initial state at the entrance face of the sound fields to the completely incoherent state as a function of the sound pressure.

ISSN:0030-3909    

DOI:10.1080/713818886

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor

摘要:

The IDRI effect in a crystal of LiIO3is well pronounced when an intense laser beam is used (E ­ 105V/cm). The effect causes sharp bending of the fundamental ray due to the refraction at the exit face of the crystal whereas the SH does not show such a behaviour, due to the weak field associated with it. This effect is shown experimentally using a laser beam of energy 1·79 eV which is focused near the exit face of the crystal (0·191 cm) of thickness 0·364 cm. The focused laser beam creates opaque sharp edges of size 6 w which produce the fine structure of the ruby radiations due to diffraction. Simultaneously, SHG yields a Fraunhoffer diffraction pattern due to the focusing. The effect of focusing increases the rate of various processes considerably (degradation of SH power, SH structure formation, radiation-induced damaging of the crystal, broadening of the central maximum and the ratio of the first maximum to the last maximum of SHG). The previous results are explained and some new results are verified in the light of the theoretical and experimental approaches. It has been shown independently that the focusing parameter () is always associated in the experiments even with the unfocused laser beams, due to the self-focusing effect which is also expected from theory.

ISSN:0030-3909    

DOI:10.1080/713818884

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor

摘要:

We report the results of a simulation, using diffuse laser light and an optical bench, of our recent holographic interpretation of Labeyrie's speckle interferometry. Our approach applies to a wide class of multiple objects (such as close binary, or higher order, stars) viewed through a turbulent medium (such as the atmosphere, under all ‘seeing’ conditions). Our results should encourage astronomers to attempt to image those multiple star systems whose individual components would be resolvable in large telescopes were there no atmosphere to contend with, but whose details are always, or usually, obscured by atmospheric seeing. We find that we can get clear images of collections of small, isolated objects after processing only 20 speckle interferograms (we must emphasize, though, that the signal to noise ratio is high in our experiments i.e. each interferogram contains several hundred speckles). We find that our reconstructions of large, continuous objects are recognizable, although appreciably distorted. We attribute this to the virtual unavoidable non-linearities introduced by our processing methods, which are entirely optical and photographic. We suggest that improved results would be obtained by a suitable combination of optical and digital processing procedures. We point out that our results support those who hope to improve the performance of inferior optical instruments by using processing methods inspired by statistical concepts.

ISSN:0030-3909    

DOI:10.1080/713818881

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor

ISSN:0030-3909    

DOI:10.1080/716099344a

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor

ISSN:0030-3909    

DOI:10.1080/713818883

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor