  In astronomy or biological imaging, refractive index inhomogeneities of e.g.
atmosphere or tissues induce optical aberrations which degrade the desired
information hidden behind the medium. A standard approach consists in measuring
these aberrations with a wavefront sensor (e.g Shack-Hartmann) located in the
pupil plane, and compensating them either digitally or by adaptive optics with
a wavefront shaper. However, in its usual implementation this strategy can only
extract aberrations within a single isoplanatic patch, i.e. a region where the
aberrations remain correlated. This limitation severely reduces the effective
field-of-view in which the correction can be performed. Here, we propose a new
wavefront sensing method capable of measuring, in a single shot, various pupil
aberrations corresponding to multiple isoplanatic patches. The method, based on
a thin diffuser (i.e a random phase mask), exploits the dissimilarity between
different speckle regions to multiplex several wavefronts incoming from various
incidence angles. We present proof-of-concept experiments carried out in
wide-field fluorescence microscopy. A digital deconvolution procedure in each
isoplanatic patch yields accurate aberration correction within an extended
field-of-view. This approach is of interest for adaptive optics applications as
well as diffractive optical tomography.
