Color and Efficiency of Luminescent Light Sources

Calculations have been made for the color and luminous efficiency of single phosphors and of blends of such phosphors. In the latter case, all the emission is assumed to come from the phosphors so that the results apply to cathode-ray tubes or to electroluminescent lamps, but not to fluorescent lamps. In these calculations it is considered that (1) real phosphors have somewhat asymmetrical spectral emission distributions of appreciable width, and (2) phosphors are quantum emitters so that the energy output from a red emitter will be lower than that of a blue emitter of equal quantum efficiency. In the case of phosphors to be used in blends, two preferred peak wavelengths at 445 and 570–590 mμ, as well as an unfavorable region at 500–505 mμ, are found. The existence of these special regions can be explained on the basis of the CIE tristimulus functions.