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Published April 2019 | Published
Journal Article Open

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.

Additional Information

© 2019 The Authors. Published by SPIE under a Creative Commons Attribution 4.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI. Paper 19009 received Feb. 4, 2019; accepted for publication Apr. 17, 2019; published online May 13, 2019. We thank Pim Venderbosch, Chris van de Stadt, and Cock Harteveld for help with setting up the experiments. We thank Matthijs Velsink for advice regarding the design of the ray tracing program. We thank Pim Venderbosch, Haider Zia, Sisir Yalamanchili (Caltech), and Thomas Russell (ETC Solar), the Caltech ETC team and the COPS chair for helpful discussion. We thank Peter Van den Wyngaert – www.littleplanet.be for photo usage permission. R.S. was funded by the University of Twente tenure-track start-up funding. L.M. acknowledges Lawrence University, Wisconsin, USA, for funding to be awarded as part of the Lawrence University Research Fellow (LU-RF) program.

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