  We theoretically investigate droplet quasi-Bessel beams for different shapes
of the round-tip axicon. Exact solutions for the Fresnel diffraction integrals
describing the axial distribution of the electric field amplitude behind the
axicon are demonstrated. The analysis of the exact solutions shows that the
period of {\guillemotleft}light droplets{\guillemotright} is not a constant
value, but depends on the axial distance and on the deviation of the axicon
surface from the conical shape far from the rounded region. The predicted
effect can be applied for the reconstruction of the exact shape of the axicon
surface without 3D scanning.
