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Three experimental arrangements for observing Fraunhofer diffraction patterns (a) with an expanded laser beam illuminating the mask, and a converging lens which gives the diffraction pattern in its focal plane (b) visually, viewing a distant point source of monochromatic light and putting the mask directly in front of the eye pupil (c) a point star observed by a telescope, where the mask is the telescope aperture. Fig. 3.4. Three experimental arrangements for observing Fraunhofer...

Simulated images of exoEarths obtainable with the Exo Earth Imager

It is interesting to speculate on how a vegetated planet might look from such enormous distances. The simulated image of an exo-Earth shown in figure 9.1(c) has 50 x 50 resolution elements (resels). It was calculated from a satellite picture of the Earth, convolved with the spread function of a nonredundant 150-aperture array shown in figure 9.1(c). It was then multiplied by the image envelope, as shrunk by the pupil densification. Some contrast enhancement was finally applied to correct the...

An Introduction To Optical Stellar Interferometry

NISENSON Cambridge, New York, Melbourne, Madrid, Cape Town, Singapore, Sao Paulo Cambridge University Press The Edinburgh Building, Cambridge cb2 2ru, UK Published in the United States of America by Cambridge University Press, New York www.cambridge.org Information on this title www.cambridge.org 9780521828727 A. Labeyrie, S. G. Lipson, and P. Nisenson 2006 This publication is in copyright. Subject to statutory exception and to the provision of relevant...

Masking the aperture of a large telescope

Despite its restriction to bright objects, we shall first discuss the application of Fizeau's and Michelson's method of aperture masking, since it is a good introduction to speckle methods and has recently had some nice applications to bright stars. It is probably fair to say that, given enough light, aperture masking gives the closest approach to diffraction-limited images of compact objects attainable through the atmosphere. For more complicated objects, the method is restricted by the...

Peter Nisenson 19412004

Peter received his BS degree from Bard University in New York, and continued with post-graduate work in Physics and Optics at Boston University. He was then employed as an optical scientist by the Itek Corporation in Lexington, MA, where he worked for 14 years. Both of us first met him there in 1973. At that time he was working on a programmable optical memory device (the PROM) which used a photoconducting crystal as a recording medium. When he first heard...

Superposition

So far we have discussed individual waves, each having a sinusoidal profile. In fact, most waves are more complicated than this but fortunately, in a linear medium, the more complicated waves can always be expressed as a weighted sum of many individual simple waves. In most cases (including, in particular, electromagnetic waves) this summation is simple one considers the propagation of each wave individually, and then sums the results. This idea is called superposition. The way in which a...

Apodization

If an image, focused by a lens or a telescope, contains light from a bright source concentrated in a small region, the bright source always contaminates the surrounding pixels, beyond its geometric image, with diffracted light, thus affecting the detection of images from adjacent fainter sources. Part of this light is diffracted by the abrupt edges of the imaging lens or mirror and appears in the form of the concentric rings in the classical Airy pattern. Obscurations such as a spider structure...