7 September 2006 Formation of contaminant droplets on surfaces
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The effects of molecular film contamination on optical systems depend strongly on the film uniformity and thickness. Molecular films of uniform thickness are responsible for light transmission losses through absorption. For example, a partially darkened film of dioctyl phthalate 100 Å thick may cause losses of about 2% in the visible spectrum. However, Ternet, et al, Villahermosa, et al, and others, have shown that scattering from droplets or "puddles" can cause transmission losses of 30%. In this paper, we examine properties of the contaminant and surface that drive the formation of smooth films and droplets. It is shown that surfaces play a strong, and sometimes dominant role in controlling film or droplet formation. DC 704, a high purity, siloxane liquid, is shown to assume both droplet and smooth film character depending on the surface.
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Kenneth T. Luey, Kenneth T. Luey, Dianne J. Coleman, Dianne J. Coleman, } "Formation of contaminant droplets on surfaces", Proc. SPIE 6291, Optical Systems Degradation, Contamination, and Stray Light: Effects, Measurements, and Control II, 62910G (7 September 2006); doi: 10.1117/12.678563; https://doi.org/10.1117/12.678563

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