(under subclass 216) Subject matter having an integrating sphere in the optical path between light source and photocell.
(1) Note. An integrating sphere is a hollow body having an interior of highly light reflecting but also diffusing material, and having relatively small openings in the shell of the hollow body to admit light. It has the property of raising the interior illumination to a level which depends only upon the amount of light flux entering the openings and not upon the reflection or diffusion of that incident light flux.
