  For an analysis of microlensing observational data in case of binary
gravitational lenses as well as for an interpretation of observations of high
magnification events in multiple images of a lensed quasar it is necessary to
calculate for a given source the microlensing light curve by a fold caustic.
This problem comes to the numerical calculation of a singular integral. We
formulated the sufficient condition of a convergence of the integral sum for
this singular integral. The strictly approach to the problem of a comparison of
model results with the unequally sampled observational data consists in
calculation of the model light curve in equidistant points of the canonical
dissection of the integration segment and a following interpolation of its
values at the moments of observations.
