Measurements of the spatial angular variability of an internally illuminated integrating sphere have been made in the interest of using such a sphere to calibrate instruments with large angular fields of view. Spatial uniformity across a 29.8-cm aperture was found to be 1.9% or better for full twelve-lamp illumination and 2.6% for one-lamp illumination. Angular uniformity from normal to ±40° was found to be 3% or better.
Warren A. Hovis and John S. Knoll, "Characteristics of an internally illuminated calibration sphere," Appl. Opt. 22, 4004-4007 (1983)