A hierarchical phasing algorithm for multi-element optical interferometers

Large multi-aperture interferometers are expected to provide snap-shot images with milli- to nano-arcsecond resolution, directly at the combined focus. This requires a densified exit pupil and phased beams for all the wavelengths used. The wave analysis methods serving for adaptive optics in monolithic telescopes being inadequate for diluted apertures, we have developed a different phasing algorithm. It involves a hierarchy of aperture triplets and uses image sharpness criteria. Numerical simulations on unresolved and resolved objects show that a single iteration is generally sufficient. On wavelength-dependant objects, the proper position indexing of the monochromatic image components appears also efficiently achievable.