Abstract

Interferometric, or aperture synthesis, imaging of faint astronomical objects requires large collecting aperture diameters. For ground-based imaging, the presence of the atmosphere serves to limit the aperture diameters to values no greater than r_o, the atmospheric spatial coherence scale, unless the star wave front is processed adaptively or otherwise. We present here an application of low-pass spatial filtering as a technique of enhancing the spatial coherence in each aperture beyond r_o by eliminating the high spatial frequencies of the atmospherically induced wave-front aberrations. We shall show that although spatial filtering of a wave front reduces the signal power throughput, reduction is more than compensated for by the increased spatial coherence in each aperture. By analyzing the coherence loss factor in a two-aperture Michelson stellar interferometer, we demonstrate a clear improvement of the sensitivity of the interferometer when a spatial filter is used in each arm. A possible implementation of spatial filters in an adaptive optics setup will also be discussed.

© 1992 Optical Society of America