CONVERTING A THREE PRIMARY COLOR INPUT SIGNAL INTO FOUR DRIVE SIGNALS

摘要

A method of converting a three primary color input signal comprises a first, a second, and a third input signal (Cl, C2, C3) into a four primary color drive signal comprising a first, second, third, and fourth drive signal (Pl, P2, P3, P4) for driving four primary colors of a multi-primary color additive display (3). Three functions (Fl, F2, F3) representing the first, second, and third drive signal (Pl, P2, P3) as a function of the fourth drive signal (P4) are defined. The intersection values (P4i) of the fourth drive signal (P4) are determined at a set of intersections of: the three functions (Fl, F2, F3) mutually, and of the three functions (Fl, F2, F3) and a line (F4) defined by the fourth drive signal (P4) being equal to itself, wherein only the intersection values (P4i) of functions having opposite signs of their first derivative are relevant. The associated first, second and third drive signals (Pl, P2, P3) are calculated at (i) the intersection values (P4i) of the fourth drive signal (P4) to obtain calculated values (CVl, CV2, CV3), and (ii) at boundary values (P4min, P4max) of a valid range (VR) of the fourth drive signal (P4) wherein all drive signals (Pl, P2, P3, P4) have valid values. The values of interest (CVl, CV2, CV3, P4i) comprising the intersection values (P4i) of the fourth drive signal (P4) and the associated calculated values (CVl, CV2, CV3) are determined. The maximum value (Vmax) or minimum value (Vmin) of the values of interest (CVl, CV2, CV3, P4i) at the intersection values (P4i) are calculated. And finally, the intersection value (P4i) at which the maximum value (Vmax) or minimum value (Vmin) is minimum or maximum, respectively, is selected.