“…This progress makes it recently interesting to use these devices as light sources for projection applications. Compared with traditional light sources, for example the mercury arc discharge lamps, LEDs have numerous advantages 1,2 . They are small and robust, have a longer lifetime, exhibit a relatively narrow spectral emission band, resulting in a larger color gamut, and are directly available in R, G, B colors; the supply voltage is lower, they can switch on and off very rapidly, have a high dimming ratio that can be used to improve the contrast, they emit no UV, do not contain dangerous mercury etc.…”