Polychromatic source calibration by one or more spectrally filtered photodetector currents

A system for establishing intensity and spectral distribution of radiation emitted by a light source comprising:

• means for energizing the light source with electric current to emit radiation;
• photodetector means for detecting the radiation in a plurality of frequency bands, said photodetector means having a fixed relationship between radiation incident upon said photodetector means and photodetector current outputted by said photodetector means in response to the incident radiation;
• means for simultaneously monitoring current outputted by said photodetector means in response to radiation incident upon said photodetector means from the light source, said monitoring means providing an indication of radiation intensity at each of said plurality of frequencies of an actual spectral distribution of the radiation, said actual spectral distribution being dependent on an amount of power inputted to the light source by said energizing means;
• means for comparing said actual spectral distribution with a reference spectral distribution to obtain a differential distribution of the radiation;
• altering means for activating said energizing means to alter the actual spectral distribution of said radiation to decrease and/or increase said differential distribution;
• and
• means for adjusting the intensity of the radiation to produce a reference value of photodetector current, the reference value of photodetector current indicating a reference value of radiation intensity.