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For an integrating sphere illuminated with a given optical power, calculates the irradiance on its surface, its radiance and the output power as functions of the input optical power, the sphere diameter, the entrance aperture diameter, the output aperture diameter and the albedo.
It is assumed that the light enters through a circular aperture (entrance aperture) with a diameter Dint. It is also assumed that a circular part of the integrating sphere (output aperture) with a diameter Dout is not diffusing and may be dedicated to the light output or to the irradiance measurement, or to any other use.