Scalar Irradiance (E_o)

A scalar irradiance collector responds equally to light coming from all directions.  The photograph shows a QSP-2200 which is equipped with a solid Teflon^® sphere to collect irradiance over 3.8 pi steradians of solid angle.  A variety of other approaches have been taken, including hollow diffusing glass spheres and paired 2π hemispheres.   Part of the logic behind using the scalar collector is that the light-collecting geometries of many photosynthetic organisms are thought to be better represented by sphere-shaped collectors rather than flat plates.