We present studies of very rich polarization phenomena observed in the light diffracted from regular
geometrical patterns. The ratio of the field amplitudes for the p-and 8-polarized light is accessible in
standard ellipsometric measurements. Forward calculations based on a scalar diffraction integral predict
ellipticity and phase shifts in the specular and higher-order beams. Both one- and two-dimensional patterns
created in general planar filmed structures are dealt with. We identify effects related to propagation
of light in the film system, i.e., to the film thicknesses and their optical properties. Characteristic features
due to the in-plane geometrical arrangement are also identified, especially, the effects of the transient
regions between the neighboring plane segments.