  We show that, contrary to popular belief, non only diffraction-free beams may
reconstruct themselves after hitting an opaque obstacle but also, for example,
Gaussian beams. We unravel the mathematics and the physics underlying the
self-reconstruction mechanism and we provide for a novel definition for the
minimum reconstruction distance beyond geometric optics, which is in principle
applicable to any optical beam that admits an angular spectrum representation.
Moreover, we propose to quantify the self-reconstruction ability of a beam via
a newly established degree of self-healing. This is defined via a comparison
between the amplitudes, as opposite to intensities, of the original beam and
the obstructed one. Such comparison is experimentally accomplished by tailoring
an innovative experimental technique based upon Shack-Hartmann wave front
reconstruction. We believe that these results can open new avenues in this
field.
