Visual appearance of microcontacts for solar windows

We explore the visual appearance of microscale silver grids for use in solar windows. The distortion of view is investigated by ray optical computations and experiments. We find that the visual appearance strongly depends on the geometric properties of the microcontacts (i.e., shape, aspect ratio, and periodicity) as well as on the viewing angle. From a perpendicular view, glass substrates appear marginally darker with microcontacts. In the case of effectively transparent triangular cross-section microcontacts, observation of scenes under a steep angle with respect to the substrate leads to the appearance of "ghost images." Scenes are projected through redirection of rays by triangular cross-section microcontacts which can be tuned by adjusting aspect ratio and periodicity.