摘要:

Moiré patterns can be calculated from the vector sums and differences of the spatial frequencies of the generating grids taken locally at various points in the field of overlap. Thus the spatial frequency at any point on a zone plate is given by the vector from that point to the zone-plate centre. Consequently two overlapping zone plates always give a difference moiré pattern represented by the distance between their centres. The analysis has been applied to a number of cases, involving line grids, zone plates, Girard grilles, and sets of equispaced concentric circles. In the latter case unequal sets give rise to a set of Cartesian ovals.

ISSN:0030-3909    

DOI:10.1080/713819386

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

A general relationship between potential functions and moiré patterns can be realized in a number of forms. The potential function can be worked as an optical surface and combined with other potential functions similarly worked to give the solution to a complex potential problem. Contour fringes can be produced from the optical surfaces or generated on a computer graph plotter directly. When superimposed these contour lines generate moiré fringes which are also solutions to potential function problems but with an essential ambiguity of sign. Two circularly symmetrical potential wells have been contoured and moiré fringe solutions to simple problems are given.

ISSN:0030-3909    

DOI:10.1080/713819381

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

Defocused pictures are restored by the convolution operation with a special scanning aperture. The scanning aperture has a circular shape with an extent smaller than twice that of the defocused point-spread function, and is divided into ten concentric rings with equal separation. The restoration experiment is executed using a digital computer image-processing system, and some experimental results evaluating the effectiveness of the aperture are described.

ISSN:0030-3909    

DOI:10.1080/713819389

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

Light interference microscopy has been used to characterize 50 to 100 μm o.d. glass microbubbles for use as laser fusion targets. In support of this programme, we have written a parallel-light, ray-trace code that follows the refracted paths of rays passing through the microbubbles. The code ultimately calculates the increase in optical path length as one moves from rays passing through the centre of the microbubble to those at the edge. The code also predicts four types of ray paths, of which only two are strong enough to produce measurable light in the interference microscope. Most interesting is the code's prediction of a forbidden zone in which no interference fringes appear. Attempts to verify this effect with laser target microbubbles gave inconclusive results because of improper dimensions and lack of sphericity in the microbubbles. Experiments with high-refractive-index, thick-walled glass cylinders might confirm the code's predictions.

ISSN:0030-3909    

DOI:10.1080/713819384

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

Die vorliegende Arbeit stellt einen Beitrag zur Laser-Doppler-Anemometrie dar und beschäftigt sich mit theoretischen Untersuchungen über maximal mögliche Signal-Rausch-Verhältnisse von Laser-Doppler-Signalen. Es sind damit Aussagen über die erreichbare Meßgenauigkeit möglich. Es werden theoretische Berechnungen zur Lichtstreuung kleiner Teilchen beschrieben, die mittels eines bestehenden Computerprogramms für Zweistrahlanemometer durchgeführt wurden. Mittels dieses Programms wurde die Streulichtintensität einschließlich der Modulationstiefe des Laser-Doppler-Signals in Abhängigkeit vom Winkel zwischen den beiden Strahlen und dem Aperturwinkel der Auffangoptik berechnet. Ergebnisse dieser Berechnungen sind in Diagrammen angegeben. Der Einfluß verschiedener Detektortypen auf Laser-Doppler-Signale wird in der vorliegenden Arbeit beschrieben und Signal-Rausch-Verhältnisse sind für verschiedene Detektoren als Funktion der Lichtleistung und der elektronischen Komponenten des Detektors angegeben. Ein Vergleich verschiedener Detektortypen zeigt, daß Photomultiplier bei Messungen der Geschwindigkeit kleiner Teilchen heranzuziehen sind. Neuere Entwicklungen von Avalanche-Photodioden haben zu Photodetektoren geführt, die bei LDA-Messungen zu Signalqualitäten führen, die in einigen Bereichen mit denen von Photomultiplier vergleichbar sein sollten.

ISSN:0030-3909    

DOI:10.1080/713819378

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

Polarizing beam-splitters of the cemented cube form are considered and the designs of a number of multilayer thin-film coatings of ZnS and cryolite giving polarizing efficiencies at the design wavelength of greater than 99·8 per cent are discussed. The refractive index of the cube is chosen to match that of the optical cement, so that wedge fringes due to the cement layer are eliminated.

ISSN:0030-3909    

DOI:10.1080/713819379

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

This paper deals with the problem of microscopic image formation using sources of non-uniform distribution. In the case of partially coherent imagery the source distribution plays a significant role in the final image quality. The question is here discussed from the point of effective transfer function of the system and also from two-point resolution. Some interesting results are obtained and it is suggested that, depending upon the object structure, different source distribution might be optimized with respect to different image assessing criteria, e.g. effective transfer function or two-point resolution.

ISSN:0030-3909    

DOI:10.1080/713819387

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

A new method of computing the reflection coefficients of a stratified medium with discontinuously or continuously varying refractive indices is presented. The method is exact for any film thickness and simple from a computational point of view. Uniaxial anisotropy in the film is allowed for.

ISSN:0030-3909    

DOI:10.1080/713819390

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

ISSN:0030-3909    

DOI:10.1080/713819383

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

ISSN:0030-3909    

DOI:10.1080/713819380

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor