Comparison of monochromatic and polychromatic modeling of sparse-aperture image quality

Optical sparse-aperture (SA) telescopes are a promising new technology to increase the effective diameter of a telescope while reducing its weight and possibly decreasing its stowable size. An SA system is constituted of an array of sub-apertures that are phased to synthesize a telescope with a larger effective diameter than any of the constituent sub-apertures. SAs were first proposed in 1970 and have been under study ever since. This paper introduces a model to simulate the performance of a sparse-aperture system including the spectral effects introduced by the differential spectral scene content and differential phase distortion at spectral sub intervals within the overall spectral bandpass of the sensor. The results indicate that when the root mean-square optical path difference from the prescription is small (i.e. < 0.10//spl mu/m) more traditional quasi monochromatic approximation introduce relatively small errors. However, when the larger, perhaps more realistic, error levels are simulated the spectral model and the quasi monochromatic or gray-world models deviate significantly pointing to the value of the spectral approach described here.