A New High-Efficiency Parallax Mask Color Tube

The electron transmission through the parallax masks of present-day tricolor tubes is about 12 per cent, thus placing a limit on picture brightness. This paper describes a new tube employing a parallax mask maintained at a potential much lower than that of the screen and a collector mesh maintained at anode potential intermediate to the screen and mask potentials; the brightness of the tube is increased 3-4 fold by virtue of enlarged mesh holes and the ensuing post-deflection focusing. In addition, secondary emission from the mask, which would dilute color, is minimized. In contrast to other post-accelerating tubes, the mask holes and fluorescent screen dots are uniformly spaced over the entire target area. Nineteen-inch round and twenty-four-inch rectangular tubes incorporating the new principle have been built.