Abstract

Traditional optical performance criteria such as resolution and encircled energy are woefully inadequate for specifying image quality for many phased telescope array applications. Variations in the subaperture geometry which produce only subtle effects on the core of the point spread function may produce highly undesirable artifacts or spurious images as well as a modulation transfer function (MTF) which exhibits zero (or negligible) values over substantial regions within the cutoff spatial frequency characteristic of a filled aperture circumscribing the array. Clearly, some minimum value of the MTF exists below which spatial information cannot be retrieved in the presence of noise. The MTF thus becomes the image quality criteria of choice for those applications where fine detail is required from extended objects. Phased telescope arrays also suffer from severe field-of-view limitations (perhaps as small as a few tens of seconds of arc) due to both pupil-mapping errors and the somewhat benign field curvature of the individual telscopes making up the array. This rapid degradation of off-axis optical performance affects target acquisition and tracking as well as imaging applications.

© 1986 Optical Society of America