PHASE ERRORS IN NEAR-AXIS BISPECTRAL STELLAR IMAGE-RECONSTRUCTION

Least-squares phase recovery from the near-axis, triple-correlation bispectrum of atmospherically degraded stellar images has been studied for a wide range of light levels, increasing object complexity, different degrees of atmospheric severity, and number of bispectral subplanes used. As one would expect, image quality improves with increasing number of subplanes used, but this improvement is greatest in the region where photon noise dominates and the amount of improvement increases with object complexity. At high signal-to-noise ratios the near-axis Knox-Thompson transfer function has a higher phase variance than the triple-correlation transfer function. Simulation and analysis confirm this result.