Anomalies in integrating sphere measurements on structured samples.

Anomalies are reported in total and diffuse reflectance values obtained from measurements on structured samples with a double-beam integrating sphere. It is demonstrated that these anomalies are caused by an interplay between the sample structure and geometric sphere imperfections. The sample structure causes a confinement of the diffuse reflectance which may suffer port losses as well as erroneously high signal levels. This can lead to deviations in the recorded reflectance values as high as 50%.