G. 4 is a block diagram showing another constitution of three primaries dividing section of the first embodiment. [0014]FIG. 5 is a block diagram showing still another constitution of three primaries dividing section of the first embodiment. [0015]FIG. 6 is a sectional view showing another example of a constitution of a screen of the first embodiment. [0016]FIG. 7A and FIG. 7B are a front view and