  Paths of particles, emitted from distributed sources and passing out through
slits of two gratings, $G_{0}$ and $G_{1}$, up to detectors, have been computed
in details by the path integral method. The slits are represented by Gaussian
functions that simulate fuzzy edges of the slits. Waves of matter be computed
by this method show perfect interference patterns both between the gratings and
behind the second grating. Coherent and noncoherent the distributed particle
sources reproducing the interference patterns are discussed in details.
Paraxial approximation stems from the wave function when removing the
distributed sources onto infinity. The more hard-edged slits of the grating
$G_{1}$ are examined by simulating those slits by a superposition of more hard
the Gaussian functions.
  As for the particles here we consider fullerene molecules. De Broglie
wavelength of the molecules is adopted equal to 5 pm.
