Glinting and shadowing, problems in lighting three-dimensional objects, can be reduced with uniform illumination. Spherical, hemispherical and ring illuminators are discussed in terms of uniformity, efficiency and practicality. For diffuse surfaces, ring illuminators are satisfactory. For specular surfaces, constant luminance reduces glint and makes the surface visible. High luminance uniformity requires external sources. A high-reflectance integrating enclosure increases both uniformity and the efficiency.
Gordon T. Uber,
"Uniform Illuminators For Inspection", Proc. SPIE 0850, Optics, Illumination, and Image Sensing for Machine Vision II, (12 March 1988); doi: 10.1117/12.942855; https://doi.org/10.1117/12.942855