Retroreflectance measurements of photometric standards and coatings Part 2

Abstract
Measurements of the opposition effect (brightening in the retroreflectance direction) have been extended to geometries with the normal of reflecting surface tilted up to 60° from the incident direction. Surface tilt appears to have little or no effect on the retroreflecting properties of MgCO3, BaSO4 paint, colloidal sulfur, or white Nextel paint for 0.6328-μm laser or 0.6-μm low coherence illumination. Source collimation–sensor acceptance angle decrease from 1° with 0.6328-μm laser illumination increases the opposition effect. The theoretical explanation of the effects observed may lie in the use of the Mie theory for highly collimated incident radiation.

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