Absolute reflectometer for the 0.8–2.5-μm region

A reflectometer based on an integrating sphere operating in the 0.8–2.5-μm region is described. The reflectometer is of the absolute type and does not need a standard diffuse reflecting surface to obtain absolute reflectance values. The system is fully automatic, using computer-controlled circular variable filters as monochromators. Results for BaSO4 in the region between the visible and 2.5 μm show considerable deviations from the accepted values of reflectivity for this substance.