The tube has a light surface with regularly arranged red, green and blue strips and index strips. The surface is scanned with a single electron beam. The beam position is controlled according to an index signal. Each strip region is divided into a grid structure and the red, green and blue strips are arranged in the horizontal direction at regular intervals of one mesh width. The index strips (I1-I5) are arranged at regular intervals of 3 and 1 mesh widths in the horizontal and vertical directions respectively and are shaped as vertical ellipses so as to connect the upper and lower edge regions of the corresp. grid positions.
