  We simulate the polarized radiative transfer in vicinities of the UX Ori type
stars during their minima. Our model of an eclipse by an extended disc
perturbation generalizes the compact gas-dust cloud eclipse model. We apply the
radiative transfer method based on enumeration using the directions grid to
model the influence of the perturbation extensions along azimuth and radius on
the eclipse depth and parameters of the linear polarization. We investigate
eclipses both for the flared disc and for the disc with a puffing-up in the
dust sublimation zone. The puffing-up is obtained by adding a disc wind to the
model. Comparison with a compact cloud eclipse model reveals that the eclipse
by a large-scale azimuthally extended perturbation may be significantly deeper
and show a greater linear polarization degree. We also demonstrate that the
perturbation extension together with the disc puffing-up can strongly affect
the degree of polarization and colour index of the star during the eclipse. The
position angle of the linear polarization may also change markedly during and
after an eclipse by a large scale perturbation for the model with a puffed-up
inner rim. Also, in this model, the maximum degree of the linear polarization
can be achieved not at the brightness minimum but closer to the end of the
eclipse. We discuss the modelling results in the context of the
photopolarimetric observations of UX Ori stars.
