  Focal plane wavefront sensing is an appealing technique to cophase multiple
aperture telescopes. Phase diversity, operable with any aperture configuration
or source extension, generally suffers from high computing load. In this
Letter, we introduce, characterize and experimentally validate the LAPD
algorithm, based on a fast linearized phase diversity algorithm \rev{with a
capture range comparable to classic phase diversity.} We demonstrate that a
typical performance of lambda/75 RMS wavefront error can be reached.
