Spatial irradiance interferometry with sources of arbitrary symmetry*

Abstract
A major limitation of irradiance interferometry in both the space and time domains has been that only sources of even symmetry could be uniquely inferred from far-field irradiance correlations, because only the modulus was derived. However, this restriction can be removed by processing, in addition, the field in a simple way before detection to form a new symmetrized function. This irradiance record corresponds to the radiation pattern derived from the pure even part of the radiance profile. The record is autocorrelated, as before, yielding a spatial power spectrum. But by the central-ordinate and hermitian properties of the spatial Fourier transform, the real part of the transformation can be specified exactly from the symmetrized record. Using the modulus of the total transform together with the real part of the transform, the phase can be inferred with only an ambiguity of sign. Thus a pair of images is derived, one erect, the other inverted. This ambiguity can be resolved, however, by moving the source in a known direction off axis.

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