Investigation of the uniformity and ageing of integrating spheres

A diode laser device was used to investigate the uniformity and ageing of typical integrating spheres. The device could be rotated about two axes enabling the input laser beam to be positioned sequentially at any point inside the sphere. For each point the resulting reflected beam flux was collected by a photodiode at a fixed position. The measurements were repeated at an interval of several months to determine if the degree of uniformity had changed. Three spheres, each incorporating a different internal white reflecting surface, were investigated. The results of sphere uniformity and temporal stability are discussed. (C) 1999 The National Physical Laboratory. Published by Elsevier Science B.V. All rights reserved.