Intensity modulation in each i-th image of the polarization set of four coronal images expressed in Eq. (4) as a function of the “polar angle”, α, shown in Fig. 5. The LCVR retardances, δ_i, were derived from the regression in Eq. (5). The data come from a quadruplet acquired during the “roll n.0” of the IT-7 campaign (June 8, 2020; Fig. 8) for a fixed heliocentric height (620 pixels from the Sun center in this particular case).