Correction of port reflection effect for integrating sphere-based reflection measurements

Abstract

We investigate the effect of port reflection in reflection measurements. Due to a high reflection coating of a sphere, the sphere's ports have thick edges, which cause reflection and contribute to the reflectance of the sphere. When the sphere is used in reflection measurements, the measured result may show a discrepancy with the theoretical prediction dealing with an ideal sphere with non-reflecting ports. To correct the reflection effects occurring at the port edges, we analytically calculate the contribution of the port edge reflection to the sphere reflectance and obtain a new correction factor for the absolute reflection measurement of Sharp and Little. Through a numerical calculation, we investigate the dependence of the new correction factor on the thickness of the port edges. For an experimental example, we perform a Sharp–Little measurement to determine the reflectance of a sample using the new correction factor.