Parameters
Pin : input power in the integrating sphere
Dsph : diameter of the integrating sphere
Dint : diameter of the entrance aperture (aperture through which the light illuminates the integrating sphere)
Dout : diameter of the output aperture (that can be used as a secondary source made of the illuminated integrating sphere or as an opening to a detector for measuring the irradiance in the integrating sphere or for any other purpose)
Ref : albedo of the integrating sphere
Er : irradiance on the integrating sphere
Lr : radiance of the integrating sphere
Pout : output power from the integrating sphere
