The Large Binocular Telescope (LBT), with dual 8.4 m optics on a common mount, is unique among the large-aperture interferometers. Deformable secondaries on the telescope capable of adaptive atmospheric correction allow beam combination after only three warm reflections. The design allows the implementation of two powerful uses of interferometry: suppression of starlight (or nulling interferometry) and wide-field imaging (or Fizeau interferometry). Nulling will allow detection of extrasolar planetary systems (from either zodiacal emission or giant planets) down to solar system-equivalent levels for nearby stars. This will dramatically increase our knowledge of the prevalence and make-up of extrasolar planetary systems. Fizeau interferometry will allow imaging of even complex structure at the resolution of a 22.8 m telescope. To implement these two powerful techniques the University of Arizona and NASA are collaborating to build the Large Binocular Telescope Interferometer (LBTI) a cryogenic instrument capable of sensitive interferometric observations in the infrared.
