Patent ID: 7151517

Claim:
An apparatus of driving a display device including a plurality of four color pixels, the apparatus comprising: an input unit receiving three color image signals; an image signal modifier converting the three color image signals into four-color image signals; and an output unit outputting the four-color image signals, wherein the image signal modifier (a) compares grays of the input image signals in a set of three color image signals to determine a maximum input gray (Max), a middle input gray (Mid), and a minimum input gray (Min) among the input image signals and to assign an order index to the signal set; (b) gamma-converts the Max, Mid, and Min luminance values into Γ(Max), Γ(Mid), and Γ(Min), respectively, wherein an inverse gamma conversion is indicated by Γ −1 ; (c) determines a maximum output gray (Max′), a middle output gray (Mid′), a minimum output gray (Min′), and an output white signal (W′) such that if Γ(Max)>2Γ(Min), Max′=Max, Mid′= Max Γ −1 {[Γ( Mid )−Γ(Min)]/[Γ(Max)−Γ(Min)]}, Min′=0, and W′ =Max Min/Γ −1 [Γ(Max)−Γ(Min)]; if Γ(Max)≦2Γ(Min) and 2Γ(Min)≦Γ( G max), where G max is a highest gray, Max′=Γ −1 [2Γ(Max)−2Γ(Min)], Mid′=Γ −1 [2Γ( Mid )−2Γ(Min)], Min′=0, W′=Γ −1 [2Γ(Min)]; and if Γ(Max)>2Γ(Min) and 2Γ(Min)>Γ( G max), Max′=Γ −1 [2Γ(Max)−Γ( G max)], Mid′=Γ −1 [2Γ( Mid )−Γ( G max)], Min′=Γ −1 [2Γ(Min)−Γ( G max)], and W′=Gmax; and (d) generates the four-color image signals from the Max′, Mid′, Min′, and W′ based on the order; and wherein said apparatus drives said display device according to the four-color image signals.