Byron M. Welsh

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It is well known that atmospheric turbulence severely degrades the performance of ground-based imaging systems. Techniques to overcome the effects of the atmosphere have been developing at a rapid pace over the past 10 years. These techniques can be grouped into two broad categories: predetection and postdetection techniques. A recent newcomer to the(More)
Current methods for estimating the wavefront slope at the pupil of a telescope using a Shack-Hartmann wavefront sensor (SH{WFS) are based on a simple centroid calculation of the irradiance distributions (spots) recorded in each subaperture. The centroid calculation does not utilize knowledge concerning the correlation properties of the slopes over the(More)
Turbulence has long been recognized as one of the most signiicant factors limiting the performance of optical systems operating in the presence of atmosphere. Atmospheric turbulence over vertical paths has been well characterized, both theoretically and experimentally. Much less is known about turbulence over long, horizontal paths. Perturbations of the(More)
This paper uses the fact that the discrete Fourier transform diagonalizes a circulant matrix to provide an alternate derivation of the symmetric convolution-multiplication property for discrete trigonometric transforms. Derived in this manner, the symmetric convolution-multiplication property extends easily to multiple dimensions using the notion of block(More)
In the past 10 years astronomical image reconstruction based on a variety of speckle techniques have become popular means of enhancing and improving the resolution of turbulence degraded images. These techniques are based on the Fourier processing of a large number of turbulence degraded \snapshots" or frames of the irradiance in the system's image plane.(More)
A new Fourier Series atmospheric phase screen generator is introduced. A Fourier Series (FS) is used to represent the wavefront phase as a two dimensional periodic function. The period of the function is chosen to be much larger than the outer scale of the turbulence and thus the FS accurately represents the power in the low spatial frequencies of the(More)
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