Angular Dependence of the Atmospheric Turbulence Effect in Speckle Interferometry

Publisher Website
Google Scholar
Abstract
The concepts of speckle interferometry, as developed by Labeyrie, and of speckle imagery, as formulated by Knox and Thompson, are analysed for dependence on field-of-view size. The preliminary analysis, assuming isoplanatism, rederives the results of Korff and derives the result, previously inferred by Knox and Thompson from computer simulation, that allowable spatial frequency separation for determining the difference of phase shift must be less than r 0 /λ. When the assumption of isoplanatism is dropped, results are obtained for the expected object power spectrum in speckle interferometry and for the expected bispectrum in speckle imagery, showing the dependence on angular spread for an object consisting of a pair of point sources. An angle, ϑ0, is defined (in terms of an integral over the strength-of-turbulance distribution along the propagation path) which bounds the range within which there are no significant anisoplanatism effects. It is noted that the effect of anisoplanatism is not to attenuate the information bearing signal, but rather to impose incorrect information on the signal. Thus anisoplanatism can result in incorrect conclusions with no indication that there is a problem.