
4.3 LED White Light Emissions 121
4.3 LED White Light Emissions
White light can be created with the use of different color LEDs (red, green, blue,
or yellow and blue, or four different colors) or by using a phosphor on a UV or
blue LED (UV LED with a trichromatic powder or a blue LED with a yellow
powder—YAG: Ce). Figure4.14 presents the different methods.
With three or more primary LEDs (Figures4.15 and 4.16), all colors can be
created. Red LEDs are the most sensitive to temperature and therefore corrections
need to be made as the LEDs heat up. Moreover, the light intensity and angle of
incidence of each LED must match and mix appropriatel ...