Flat image display device utilizing digital modulation

Abstract

An evacuated envelope having therein a vertical by horizontal matrix of cells. Each cell includes a line electron source; a digital modulation section; an electron accelerating and focusing region; and a cathodoluminescent phosphor screen. The digital modulation section includes a modulation mask disposed between the line electron sources and the electron accelerating and focusing region. The modulation mask comprises a metal sheet having a plurality of slots therein. Each slot is aligned within a cell and is surrounded by a sensing pad disposed on a surface of the modulation mask which faces the line electron sources, and by a modulation electrode disposed on the opposite surface. A digitally pulsed flow of electrons, produced by the line electron sources, is directed toward the modulation mask. A series of digital voltage pulses are applied to the modulating electrodes. The voltage pulses are synchronized with the digitally pulsed electron flow such that when a voltage pulse appears on the modulating electrodes the corresponding pulse from the line electron source will be denied passage through the slot in the modulation mask. The sensing pads are charged to a desired voltage in order to regulate the level of the pulses which are permitted passage through the slots in the modulation mask. The level of brightness produced at each of the cells in the matrix is a function of the number of digital pulses permitted to pass through the slots in the modulation mask as well as the level of these pulses.