摘要:

Toute tentative d'interprétation des propriétés optiques des couches minces suppose, nécessairement, une connaissance aussi exacte que possible de la structure géométrique de ces couches. En effet, celles-ci ne sont pratiquement jamais assimilables à une simple lame homogène, à faces planes et parallèles, mais ont une forme et une structure beaucoup plus compliquées. Les couches relativement épaisses sont généralement lacunaires et sont limitées par des surfaces irrégulières; les plus minces sont le plus souvent granulaires, c'est-à-dire formées par une répartition bidimensionnelle de grains séparés. En plus des méthodes classiques en microscopie électronique, on décrit une technique, qui permet de connaître exactement le profil des surfaces et la forme des grains. On donne quelques uns des résultats ainsi obtenus, notamment pour des couches lacunaires de fluorure de calcium et des couches granulaires de sélénium. L'étude optique des couches minces métalliques permet de mettre en évidence l'existence de bandes d'absorption qui ne se retrouvent pas lorsque le métal est à l'état massif ou qui font appel á des mécanismes encore mal connus. Ce sont ces bandes que l'on qualifie d'anormales. Récemment, grâce à la mise en service de groupes de pompage permettant d'atteindre des vides très poussés et à la mise au point de techniques particulières (supports refroidis) ces recherches ont été étendues aux métaux alcalins et alcalino-terreux. Les résultats obtenus seront rapidement résumés. Enfin, on a réussi à préparer des lames minces sans support, optiquement homogènes et continues, d'épaisseur égale ou supérieure à 200 Å pour les lames polycristallines et 600 Å pour les lames monocristallines, ayant une surface de l'ordre du centimètre carré.

ISSN:0030-3909    

DOI:10.1080/713818229

出版商:Taylor & Francis Group    

年代:1969

数据来源: Taylor

摘要:

Les franges de l'interférométrie holographique sont étudiées pour les mouvements types d'un objet, et la forme et la localisation des franges sont obtenues. Il résulte de ces études que le faisceau d'éclairage de l'objet est parallèle à la direction d'observation et que la séparation des franges d'égale inclinaison de celles d'égale épaisseur permet de mesurer le déplacement global et la déformation pure longitudinale et latérale.

ISSN:0030-3909    

DOI:10.1080/713818220

出版商:Taylor & Francis Group    

年代:1969

数据来源: Taylor

摘要:

Theoretical and experimental studies are described on the formation and localization of holographically produced interference fringes. The fringes were shown to be localized where the correlation between the wave fields produced by the two objects identical in shape but different in the relative position attains the maximum value. A grating model of a diffusely reflecting surface was proposed, in exact agreement with the theory. Experiments were carried out to verify the discussions.

ISSN:0030-3909    

DOI:10.1080/713818223

出版商:Taylor & Francis Group    

年代:1969

数据来源: Taylor

摘要:

A laser coherence analyser is described which yields simultaneous temporal and spatial coherence analysis of laser beams. It is of particular application to high power pulsed laser systems, for high speed holography and non-linear optics, where the short duration of the pulse (often less than 50 nsec) excludes the use of photoelectric spectrometers, employing time variation scanning of the optical path length. The instrument consists of two high quality spherical mirrors, having dielectric multilayer coatings of reflectivity typically 0.95 to 0.97, separated by a cylindrical invar spacer of adjustable length. In use, the spacer is normally set so that the pole separation of the plates is a few hundred micrometres less than their common radius of curvature (typically 10 cm). The resulting defocusing term combines with spherical aberration to yield a multiple beam interferogram having an annular region of nearly linear dispersion. Spectral resolving powers in the range 107to 108are readily obtainable. When the input beam possesses a high degree of spatial coherence, the fringes of the concentric rings interference pattern are alternately of high and low intensity, the visibility of the alternation being a direct measure of the spatial coherence. This alternation effect may be eliminated by obstructing one-half of the input aperture. Any spatial, spectral or intensity variations across the laser beam are superposed on the fringe pattern, since the spherical interferometer is not translationally invariant in a parallel beam. This is in contrast to the behaviour of a plane Fabry-Pérot etalon. The experimental characteristics of the instrument, and its properties, as predicted by numerical computation, are examined both for C.W. and pulsed lasers. The effect of the finite response time is described. This is particularly important when the coherence analyser is employed in conjunction with an image tube streak camera to obtain time-resolved spectra of pulsed systems. Both time-integrated and time-resolved fringe profiles are considered for various types of laser pulse. The effect of plate defects on fringe profiles is also considered in outline. In addition to providing quasi-linear dispersion and information on coherence and other spatial properties of the input, the instrument described has the advantages of providing high illumination, and of being easy to use in practice, the plates remaining permanently in alignment.

ISSN:0030-3909    

DOI:10.1080/713818221

出版商:Taylor & Francis Group    

年代:1969

数据来源: Taylor

摘要:

The maximum likelihood receiver (MLR) to detect a pulsed signal propagated through a turbulent medium is found under assumptions that approximate optical propagation over a long path through the atmosphere. Limiting cases of the MLR are the coherent heterodyne receiver (CHR) and the total-energy-measuring receiver. With an additional assumption, the probability of error of the MLR is approximated. The CHR, even with an optimally chosen aperture weighting function, can be markedly inferior to the MLR. Unlike the optimized CHR, the MLR can effectively use arbitrarily large apertures. A coherent optical system is given that, in principle, realizes the MLR.

ISSN:0030-3909    

DOI:10.1080/713818224

出版商:Taylor & Francis Group    

年代:1969

数据来源: Taylor

摘要:

Bei der Messung der Übertragungsfunktion optischer Systeme wird im allgemeinen zur Vergrößerung der bildseitigen Intensitätsverteilung ein Mikroobjektiv eingesetzt. Um den Einfluß von Mikroobjektiven auf die Genauigkeit der Ergebnisse der Messung von Übertragungsfunktionen zu untersuchen, wurden mit einem hochgeöffneten gut korrigierten Objektiv Messungen mit und ohne Mikroobjektiv durchgeführt. Ein früher beschriebenes Gerät [1], bei dem die bildseitige Intensitätsverteilung grundsätzlich ohne Zwischenschaltung eines Mikroobjektives abgetastet wird, wurde so erweitert, daß Messungen von Übertragungsfunktionen mit und ohne Mikroobjektiv durchgeführt werden konnten. Nur Mikroobjektive, die im Bereich der ausgenutzten Aperturen als ideale Objektive anzusehen sind, haben keinen Einfluß auf die Meßergebnisse. Auf der Achse ideal gute Mikroobjektive können bei außeraxialen Messungen von Übertragungsfunktionen des Prüflings zu beträchtlichen Meßfehlern führen.

ISSN:0030-3909    

DOI:10.1080/713818232

出版商:Taylor & Francis Group    

年代:1969

数据来源: Taylor

摘要:

This study concerns a boundary-value problem approach to the action of a lens system upon a coherent light beam. For the sake of simplicity, we assume the lenses to be cylindrical and to be composed of homogeneous perfect dielectric substances. In addition, we assume that the cross sections of the lenses are those of two intersecting circles. The solution to Maxwell's equations is sought by means of Green's identity, which permits us to express the electromagnetic field within and outside of each lens in terms of the field values on the lens surfaces. The application of the continuity relations across these same surfaces then yields a system of coupled Fredholm-type integral equations of the second kind. These are reduced, by means of the numerical quadraturing technique, to a finite-order matrix equation, the unknowns of which represent the sampled field values along the lens surfaces. For a large number of lenses and for a large number of sampling points, the inversion of the matrix equation can be accomplished, when computer memory size becomes a limiting factor, by suitable partitioning. No theoretical approximations intervene at any level of the analysis; thus the accuracy of the result is only limited by the number of sampling points and by the word-length capacity of the computer. This approach permits a quantitative measure of the behaviour of the type of diffraction-limited systems which occur in all fields of optics, especially in microscopy, and provides a tool for investigating new types of optical systems which cannot be studied by conventional optical theory.

ISSN:0030-3909    

DOI:10.1080/713818222

出版商:Taylor & Francis Group    

年代:1969

数据来源: Taylor

摘要:

Eine allgemeine, mengentheoretische Formulierung des Begriffs der Messung führt über strukturisomorphe Abbildungen zu drei Niveaus der Skalierung. Im Rahmen eines einfachen psychometrischen Modells wird die ‘Methode der ordinalen Urteilskategorien’ erläutert, eine Möglichkeit zur Quantifizierung von Empfindungsstärken. Mit Hilfe des Matrizenkalküls wird eine mögliche Lösung für die praktische Auswertung gegeben. Schließlich wird die Brauchbarkeit der Methode an experimentellen Befunden zur Bewertung der Blendung getestet.

ISSN:0030-3909    

DOI:10.1080/713818230

出版商:Taylor & Francis Group    

年代:1969

数据来源: Taylor

摘要:

In theory, an optical system with a finite aperture can be coated to produce arbitrarily perfect imagery over a limited field. When the object is of limited extent, this field can be made the optical conjugate to the object, so that the whole object is imaged with arbitrary precision. The required pupil coating approximates low-contrast cosine fringes over its central region, with a frequency and amplitude that rapidly accelerate as the aperture edge is approached. Here the maximum occurs as a narrow spike. The frequency near the central region varies directly with the total extent of the conjugate field, and inversely with the required central core width Δ in the point amplitude response. As Δ is made arbitrarily narrow, the point amplitude response approaches the form of a sinc function over the field of view. This function is precisely the point amplitude for a diffraction-limited pupil with a magnified aperture of 1/Δ times the given pupil aperture ! The only image property that is not in compliance with this effective aperture magnification is that of total illumination. This is severely reduced from that of the original, uncoated aperture, and is the major restriction on practical use of the derived pupil. Applications to microscopy and telescopy are discussed.

ISSN:0030-3909    

DOI:10.1080/713818225

出版商:Taylor & Francis Group    

年代:1969

数据来源: Taylor

ISSN:0030-3909    

DOI:10.1080/713818226

出版商:Taylor & Francis Group    

年代:1969

数据来源: Taylor