Characterization of surface cleanliness with particulate obscuration

Michael C. Fong; Aleck L. Lee

doi:10.1117/12.190135

19 October 1994 Characterization of surface cleanliness with particulate obscuration

Michael C. Fong, Aleck L. Lee

Proceedings Volume 2261, Optical System Contamination: Effects, Measurements, and Control IV; (1994) https://doi.org/10.1117/12.190135
Event: SPIE's 1994 International Symposium on Optics, Imaging, and Instrumentation, 1994, San Diego, CA, United States

Abstract

An analysis has been performed to define the obscuration ratio (OR) of surface particles by considering not only the geometric cross sections of the particles but also their irradiance absorption/scattering characteristics. This analysis shows that part of the `extinct' irradiance due to interaction with the surface particles will be recovered by the surface via forward scatter of the radiant energy flux. Over-prediction of irradiance loss based on the often used assumption of opaque particles can thus be avoided. Consideration of the combined effect of absorption and forward scatter permits defining a more realistic effective OR. Sample solutions have shown that for opaque particles, the OR would be reduced by 50%, and for dust particles, the reduction would be by a factor of 10.

Citation Download Citation

Michael C. Fong and Aleck L. Lee "Characterization of surface cleanliness with particulate obscuration", Proc. SPIE 2261, Optical System Contamination: Effects, Measurements, and Control IV, (19 October 1994); https://doi.org/10.1117/12.190135

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