The measured optical spectrum of a typical white-light
(Luxeon STAR) LED is show in Fig. 1(a). It can be seen that
the emitted white light consists of a blue component (containing
10% of the overall emitted power) from the LED and a
yellow component from the phosphor. The measured frequency
responses of different components (white, blue, and yellow) of
the emission are shown in Fig. 1(b).