Multi-beam index crt with horizontal phosphor lines

Abstract

A multi-beam color index cathode ray tube (CRT) includes vertically spaced, horizontal phosphor stripes on the inner surface of its display screen. The parallel phosphor bands are arranged in groups of three, with each phosphor stripe in a group providing a respective one of the three primary colors of red, green and blue. An electron gun directs three electron beams onto the display screen, with the three electron beams deflected over the display screen in unison in a raster pattern. The three electron beams are focused in the form of three spots on the display screen, with each spot coincident with a respective horizontal phosphor stripe of a given color. The intensity of each electron beam is independently modulated as it sweeps across the width of the display screen by a respective color video signal in accordance with the displayed image. The three electron beams are each provided with a horizontally elongated cross section, with convergence of the beams provided by a plurality of multi-pole adjustable magnets. By horizontally elongating and vertically offsetting the beams, the vertical spacing between the electron beams as well as between the horizontal phosphor stripes may be reduced for improved video image resolution. The closely spaced electron beams may be focused with a conventional main focusing lens employing a common beam-passing aperture, with electron beam alignment with the horizontal phosphor stripes provided via a beam responsive UV emitter/sensor combination and feedback control arrangement.